Plant and animal cells can be grown outside the organism they come from, and some can be propagated in cell cultures within laboratory glassware for years. Through morphic resonance, if some cells from the culture adapt to a new challenge, similar cells should be able to adapt to the same challenge more rapidly even when they are separated.

The morphic field hypothesis proposes that minds are systems of fields that are located inside brains but also extend far beyond them, just as the fields of magnets are both within magnets and extend invisibly beyond them. Morphic fields contain attractors (goals) and chreodes (habitual pathways towards those goals) that guide a system toward its end state. They effect all self-organizing systems, and systems within systems, in a nested hierarchy or holarchy of morphic units. Morphic fields of social groups may help to coordinate flocks of birds and schools of fish, which can rapidly change direction without individuals colliding.

In this paper I discuss the sense of being stared at and telepathy as natural consequences of the hypothesis of morphic fields. Although this hypothesis could perhaps account for clairvoyance, psychokinesis, and precognition, it only does so through chains of additional hypotheses, whereas possible explanations for the sense of being stared at and telepathy emerge naturally and directly from this hypothesis. I also differentiate this hypothesis from other explanatory models of psi and discuss its application to non-psi phenomena, like protein folding, inheritance, collective memory, learning, and navigation in animals.

Ervin Laszlo's concept of the Akashic Field includes the idea of a cosmic memory. This field is a universal field, and Laszlo's (2004) Laszlo, E. 2004. Science and the Akashic Field, Rochester, VT: Inner Traditions International. [Google Scholar] scientific starting point is the physics of the vacuum underlying space itself. A similar idea of a memory in nature arises from the hypothesis of formative causation, with its central concept of morphic fields. This hypothesis arose from biology rather than physics. Morphic fields help to explain embryology, biological development, habits, memories, instincts, telepathy, and the sense of direction. They have an inherent memory. In its most general form this hypothesis implies that many of the so-called laws of nature are more like habits.

Since ancient times, a strong and pervasive belief in the efficacy of prayer–for the living and the dead–reinforces the notion that consciousness is not limited to the physical body. Not only do traditions throughout the world share a belief that prayers may in some way help (or invoke help from) deceased ancestors, many cultures throughout history have believed that prayer can bring about changes in the physical circumstances of the living.

The hypothesis of formative causation predicts that as animals of a given species learn a new pattern of behaviour, other similar animals will subsequently tend to learn the same thing more readily all over the world, a a result of a process called morphic resonance. The more that learn it, the easier it should become for others. This possibility was tested with day-old chicks using a simple learned response, a conditioned aversion. The test took place in the laboratory of Steven Rose, a sceptic, following a standard procedure used routinely in his laboratory, and was carried out blind by a summer student who knew nothing of the purpose of the experiment nor of morphic resonance. The chicks were exposed either to a test stimulus, a small yellow light-emitting diode (LED), or a control stimulus, a chrome bead. Half an hour after pecking the stimulus, the control chicks received an injection of saline solution, and the test chicks an injection of lithium chloride, which made them mildly sick. They were then tested three hours later, each chick being exposed sequentially to the control and the test stimulus, when most test birds were averse to pecking the yellow LED, but not averse to pecking the control bead. The response of the chicks was measured by recording the latency, the time delay in seconds before they first pecked the stimulus. The same experimental procedure was repeated for 37 days. If morphic resonance were occurring, successive batches of chicks should have shown an increasing aversion to the yellow LED, even in the initial training procedure, by morphic resonance from their averse predecessors. The controls should have shown no such increasing aversion. I think the results are consistent with such an effect, which shows up with a high degree of statistical significance (p < 0.01) when the aversion to the yellow bead is measured relative to the control. Rose disagrees with this interpretation.

Rose's predictions about the outcome of this experiment were refuted by the empirical data. His aggressive tone and extravagant rhetoric conceal this simple fact. I will not attempt to answer his polemic, ranging from Nietzsche to ley-lines, but simply start by looking again at his predictions about the chicks: "No secular trends apparent; latencies to peck the illuminated bead after ten weeks are no different from those on week I, and the differences between latencies for illuminated and chrome beads, if they occur, are also unchanged". In fact secular trends were very apparent, latencies to peck the illuminated bead after ten weeks were very different from those on week I, and the differences between latencies for illuminated and chrome beads were not unchanged. Rose and I discussed various interpretations of the data over a period of eighteen months. At the outset, he seemed certain that the hypothesis of formative causation would be disconfirmed. He had already publicly denounced it in the strongest terms. He appeared to have no doubt that when tested in his own laboratory, under his own supervision, in my absence, by an experimenter working blind, the data would reveal no trace whatever of morphic resonance. But it soon became clear that there had been an effect of the kind predicted by the hypothesis of formative causation. (I discuss below Rose's alternative interpretation of this effect in terms of "floors" and "ceilings"). After lengthy delays, Rose withdrew from our agreement to write a joint paper, and no longer wanted to publish the results.

Ranchers throughout the American West have found that they can save money on cattle grids by using fake grids instead, consisting of stripes painted across the road. Real cattle grids, usually made of a series of parallel steel tubes or rails with gaps in between, which make it physically impossible for cattle to walk across them. However, cattle do not usually try to cross them; they avoid them. The illusory grids work just like real ones. When cattle approach them, they "put on brakes with all four feet", as one rancher expressed it to me.

In this essay, I am going to discuss the concept of collective memory as a background for understanding Jung's concept of the collective unconscious. The collective unconscious only makes sense in the context of some notion of collective memory. This then takes us into a very wide-ranging examination of the nature and principle of memory-not just in human beings and not just in the animal kingdom; not even just in the realm of life-but in the universe as a whole. Such an encompassing perspective is part of a very profound paradigm shift that is taking place in science: the shift from the mechanistic to an evolutionary and wholistic world view.

The approach I am putting forward is very similar to Jung's idea of the collective unconscious. The main difference is that Jung's idea was applied primarily to human experience and human collective memory. What 1 am suggesting is that a very similar principle operates throughout the entire universe, not just in human beings. If the kind of radical paradigm shift 1 am talking about goes on within biology ? if the hypothesis of morphic resonance is even approximately correct ? then Jung's idea of the collective unconscious would become a mainstream idea: Morphogenic fields and the concept of the collective unconscious would completely change the context of modern psychology.

This is the third in our series of essays by Rupert Sheldrake on the implications of his hypothesis of Formative Causation for the psychology of C. G. Jung. The intense controversy this hypothesis generated with the publication of his first book, A New Science of Life (1981), has stimulated a number of international competitions for evaluating his ideas via experimental investigations.

Sheldrake's paper claims that the results of the experiment which we jointly planned, and which was conducted by myself and Ms Harrison, are in conformity with the hypothesis he describes as "formative causation". Before demonstrating that Sheldrake's interpretation of these results is invalid, and that they by no means confirm his hypothesis, I wish to comment briefly on the background to the experiment. His book A New Science of Life seemed when I first read it, and still seems, to propose an entirely empty hypothesis. The circumstances in which novel hypotheses (paradigms) become important in science have been well described by Thomas Kuhn; they emerge when there is an accumulation of observational anomalies which existing hypotheses cannot account for, or when a theory becomes excessively cumbersome and "inelegant" and the alternative seems to handle the same material more coherently. To Kuhn's account we can, at least in the particular context of the present discussion, add the well-worn view that to have utility, a hypothesis should be capable of disconfirmation.

This paper examines the central theoretical concepts in the work of Rupert Sheldrake. The first section examines Sheldrake’s account of morphic fields and questions whether difficulties arise when these concepts are extended upwards from the biological level. The second section reviews Sheldrake’s concept of extended mind and considers the criticism that it is reductionist about mentality. In considering both of these criticisms it is argued that Sheldrake’s theories can be taken in a reductive direction, but need not be. The third and final section draws on the work of Joseph Bracken and David Ray Griffin to suggest a panpsychist metaphysics of field as one possible way that Sheldrake could sidestep these dangers and strengthen his approach.

Many animals escaped the great Asian tsunami on Boxing Day, 2004. Elephants in Sri Lanka and Sumatra moved to high ground before the giant waves struck; they did they same in Thailand, trumpeting before they did so. How did they know? The usual speculation is that the animals picked up tremors caused by the under-sea earthquake. This explanation seems to me unconvincing.

Aimée Morgana noticed that her language-using African Grey parrot, N'kisi, often seemed to respond to her thoughts and intentions in a seemingly telepathic manner. We set up a series of trials to test whether this apparent telepathic ability would be expressed in formal tests in which Aimée and the parrot were in different rooms, on different floors, under conditions in which the parrot could receive no sensory information from Aimée or from anyone else.

During these trials Aimée and the parrot were both videotaped continuously. At the beginning of each trial, Aimée opened a numbered sealed envelope containing a photograph, and then looked at it for two minutes. These photographs corresponded to a prespecified list of key words in N'kisi's vocabulary, and were selected and randomized in advance by a third party. We conducted a total of 149 two-minute trials. The recordings of N'kisi during these trials were transcribed blind by three independent transcribers. Their transcripts were generally in good agreement. Using a majority scoring method, in which at least two of the three transcribers were in agreement, N'kisi said one or more of the key words in 71 trials. He scored 23 hits: the key words he said corresponded to the target pictures.

In a Randomized Permutation Analysis (RPA), there were as many or more hits than N'kisi actually scored in only 5 out of 20,000 random permutations, giving a p value of 5/20,000 or 0.00025. In a Bootstrap Resampling Analysis (BRA), only 4 out of 20,000 permutations equalled or exceeded N'kisi's actual score (p = 0.0002). Both by the RPA and BRA the mean number of hits expected by chance was 12, with a standard deviation of 3. N'kisi repeated key words more when they were hits than when they were misses. These findings are consistent with the hypothesis that N'kisi was reacting telepathically to Aimée's mental activity.

Many dog owners claim that their animals know when a member of the household is about to come home, showing their anticipation by waiting at a door or window. We have investigated such a dog, called Jaytee, in more than 100 videotaped experiments. His owner, Pam Smart (PS) traveled at least 7 km away from home while the place where the dog usually waited for her was filmed continuously. The time-coded videotapes were scored "blind". In experiments in which PS returned at randomly-selected times, Jaytee was at the window 4 per cent of the time during the main period of her absence and 55 percent of the time when she was returning (p<0.0001). Jaytee showed a similar pattern of behavior in experiments conducted independently by Wiseman, Smith & Milton (1998). When PS returned at non-routine times of her own choosing, Jaytee also spent very significantly more time at the window when she was on her way home. His anticipatory behaviour usually began shortly before she set off. Jaytee also anticipated PS's return when he was left at PS's sister's house or alone in PS's flat. In control experiments, when PS was not returning, Jaytee did not wait at the window more and more as time went on. Possible explanations for Jaytee's behavior are discussed. We conclude that the dog's anticipation may have depended on a telepathic influence from his owner.

Many dog owners claim that their animals know when a member of the household is coming home, typically showing their anticipation by waiting at a door or window. In previous trials with a dog called Jaytee, recorded on videotape, it was found that he anticipated his owner's arrival more than ten minutes in advance, even when she was returning in unfamiliar vehicles such as taxis, when the people at home did not know when to expect her, and when she set off at randomly-selected times. This paper describes the results of a pre-planned series of ten videotaped trials with a dog called Kane, a Rhodesian ridgeback, who was said to wait by a window while his owner was on the way home. The window-area was filmed continuously while the dog's owner went to places more than 8 km away and came home at a variety of non-routine times, some of which were selected at random and communicated to her by a telephone pager. The time-coded videotapes were scored blind by a third party. In nine out of ten trials Kane spent most time at the window when his owner was on the way home. On average he was at the window 26 percent of the time while she was returning, and only one percent of the time throughout the rest of her absence. This difference was highly significant statistically. Possible explanations for this behavior are discussed.

This is part of an exchange between Sheldrake and Wiseman. For the complete picture see: Richard Wiseman's claim to have debunked "the psychic pet phenomenon"

In the January issue of the Journal Richard Wiseman, Matthew Smith & Julie Milton published a reply to my note (Sheldrake, 1999a) about their claim to have refuted the "psychic pet" phenomenon. This claim was made in the British Journal of Psychology (Wiseman, Smith & Milton, 1998) and widely publicized in the media. It was repeated as recently as February 2 this year in a presentation given by the first author at the Royal Institution entitled "Investigating the Paranormal".

At my invitation, Wiseman and Smith carried out 4 videotaped experiments with a dog called Jaytee, with whom I have carried out more than 100 videotaped experiments (Sheldrake, 1999b). My experiments showed that Jaytee usually waited by the window for a far higher proportion of the time when his owner was coming home than when she was not. This occurred even when his owner, Pam Smart, came at non-routine, randomly-selected times and travelled by unfamiliar vehicles such as taxis. This pattern was already clearly apparent months before Wiseman et al. carried out their tests.

In the 3 experiments that Wiseman and Smith carried out at Pam's parents' flat, the pattern of results was very similar to my own. Their data show a large and statistically significant effect: Jaytee spent a far higher proportion of time at the window when Pam was on the way home than when she was not (Sheldrake, 1999a).

This is part of an exchange between Sheldrake and Wiseman. For the complete picture see: Richard Wiseman's claim to have debunked "the psychic pet phenomenon"

In August 1998 the British Journal of Psychology published a paper entitled 'Can animals detect when their owners are returning home? An experimental test of the "psychic pet" phenomenon' by Richard Wiseman, Matthew Smith and Julie Milton. This paper was widely publicized thanks to a media release issued by the Press Office of the British Psychological Society. The sceptical tone of this announcement, entitled 'Mystic dog fails to give scientists a lead', was reflected in the ensuing newspaper reports: 'Pets have no sixth sense, say scientists' (The Independent , Aug 21); '"Psychic" dog is no more than a chancer' (The Times , Aug 21); 'Psychic pets are exposed as a myth' (The Daily Telegraph , Aug 22). The wire services reported the story world-wide.

Together with Pamela Smart, I have carried out over 200 experiments with the dog in question, called Jaytee. The four experiments that form the basis of the paper by Wiseman and his colleagues were carried out at my invitation (and with the loan of my video equipment). I would like to take this opportunity of putting into context their paper and the publicity it excited.

In 1991, Pamela Smart's (PS) parents first noticed that her dog, Jaytee, seemed to anticipate her return, apparently waiting for her at the window, beginning around the time she was setting off to come home. In May 1994, PS and her parents began to keep notes on her journeys and Jaytee's reactions. In this paper we describe the results of 96 such sets of observations made between May 1994 and February 1995, on which she went up to 51 kms away from home. Jaytee reacted 10 minutes or more in advance of PS's return on 82 occasions, and showed no anticipatory reaction on 14. There was a highly significant correlation between the time at which the dog reacted and the time at which PS set off homewards. Jaytee's reactions did not seem to be attenuated by PS's distance. In some additional experiments, his reactions occurred on 4 out of 5 occasions when PS travelled by unfamiliar means, for example in taxis. He also reacted on 4 out of 4 occasions when she set off home at randomly selected times. In one of these experiments, both Jaytee's reactions and PS's movements were recorded on videotape, and showed that the dog reacted 11 seconds after PS was told to go home at a randomly selected time previously unknown to her. The evidence suggests that Jaytee's reactions depended on an influence from his owner detected by the dog in a manner currently unknown to science.

A survey was carried out by telephone in London to find out how any pet owners had observed seemingly telepathic abilities in their pets. 52% of dog owners claimed that their animals knew in advance when a member of the household was on the way home, compared with 24% of cat owners. Of the animals that reacted, 21% of dogs and 19% of cats were said to do so more than 10 minutes before the person's return. 73% of dog owners and 52% of cat owners said their pets knew when the owners were going out before they showed any signs of doing so. 43% of dog owners and 41% of cat owners said their pets responded to their thoughts or silent commands; and 57% of dog owners and 37% of cat owners said their pets were sometimes telepathic with them. 46% of people with pets now and 37% of people without pets now said that they had known pets in the past that were telepathic. 39% of those with pets now and 38% of those currently without pets said they themselves had had psychic experiences. But significantly fewer of those who had never kept pets had had psychic experiences themselves. The results of this survey are compared with two similar surveys in North-West England and in California. The general pattern was remarkably similar in these three very different locations, and shows that seemingly telepathic abilities in pets are common. In all locations dogs were more responsive than cats to their owners' thoughts and intentions. The potential for experimental investigations of these abilities is discussed.

A telephone survey of 200 households was carried out in North-West California to find out how many pet owners claim to have observed seemingly psychic abilities in their animals. 132 of the households surveyed had pets. 45% of dog owners claimed their animal knew in advance when a member of the household was on the way home, compared with 31% of cat owners, and around 20% of these animals were said to react more than 10 minutes in advance. 65% of dog owners and 37% of cat owners said their pets knew that they were going out before they showed any physical signs of doing so. 46% of dog owners and 41% of cat owners said that their pet responded to their thoughts or silent commands, and 42% of dog owners and 34% of cat owners said that their pet was sometimes telepathic with them. 49% of pet owners and 31% of non-pet owners said that some of the animals that they had known in the past were telepathic. Significantly more pet owners claimed to have had psychic experiences themselves than non-pet owners, and a significantly higher proportion of 'psychic' pet owners claimed that their pets exhibited psychic powers than 'non-psychic' owners. These findings are in general agreement with a previous survey in England. Some implications of these results are discussed.

Pet owners often comment on the perceptivenesso f their animals.F or example, some cat owners say that their animals seem to know when they intend to take them to the vet, and disappear, even when the person has tried to give the cat no clue. And some dogs are said to know when their owners are about to return, sometimes half an hour or more in advance, even when the person comes at an unusual time or in an unfamiliar vehicle (Sheldrake,, t994). Many pet owners ascribe such kinds of perceptivenesst o telepathyo r a mysterious 'sixth sense'.

Such phenomena have, so far, been neglected by biologists and psychologists. One reason for this neglect may be the taboo, widespread among scientists, against taking seemingly 'paranormal' phenomena seriously. Another may be the taboo against taLing pets seriously (Serpell, 1986).

I and my colleagues have recently carried out three surveys to find out what proportion of pet owners have experienced a perceptiveness in their pets that might go beyond the known senses. We asked a series of questions, listed below, in telephone interviews with people in randomly sampled households. The same questionnaire was used in three separate surveys in widely different locations: Ramsbottom, a small town near Manchester, England (Sheldrake and Smart, 1997); Santa Cruz, a university and beach town in California, USA (Brown and Sheldrake, 1998); and London, England (SheldrakeL, awlor and Turney, 1998).

Of course, what people believe about their pets' abilities may not be true. But it may not be false either. Only empirical investigations can shed further light on these phenomena

A telephone survey was carried out in Greater Manchester to find out how many pet owners had observed seemingly psychic abilities in their pets. 46% of dog owners claimed their animals knew in advance when a member of the household was on their way home, compared with 14% of cat owners. Most of these animals reacted 5 minutes or less in advance, but a substantial proportion reacted 10 minutes or more in advance of the person's return. 69% of dog owners and 48% of cat owners thought there pets knew when they were going out before they showed any physical signs of doing so. 53% of dog owners and 33% of cat owners thought their pet responded to their thoughts or silent commands; and similar percentages thought their pet was sometimes telepathic with them. Just over half of those who had kept pets in the past thought that some of these animals were telepathic. More dog than cat owners claimed to have had psychic experiences themselves, and a higher proportion of "psychic" pet owners claimed that their pets exhibited psychic powers than "non-psychic" owners. The potential for experimental investigations of the seemingly psychic powers of pets is discussed.

Objective: To carry out automated experiments on mobile phones to test for telepathy in connection with telephone calls.

Study Method: Subjects, aged from 10 to 83, registered online with the names and mobile telephone numbers of three or two senders. A computer selected a sender at random, and asked him to call the subject via the computer. The computer then asked the subject to guess the caller's name, and connected the caller and the subject after receiving the guess. A test consisted of six trials.

Interactions Evaluated: The effects of subjects' sex and age and the effects of time delays on guesses.

Main Outcome Measure: The proportion of correct guesses of the caller's name, compared with the 33.3% or 50% mean chance expectations.

MainResults: In 2080 trials with three callers there were 869 hits (41.8%), above the 33.3% chance level (P < 1 x 10¹⁵). The hit rate in incomplete tests was 43.8% (P=.00003) showing that optional stopping could not explain the positive results. In 745 trials with two callers, there were 411 hits (55.2%), above the 50% chance level (P=.003). Ananalysis of the data made it very unlikely that cheating could explain the positive results. These experiments showed that automated tests for telephone telepathy can be carried out using mobile phones.

Telepathy in connection with telephone calls is the commonest kind of apparent telepathy in the modern world. It usually occurs between people who have strong bonds or emotional connections with each other, such as parents and children, husbands and wives, and good friends. In experimental tests in which subjects had to identify who, out of four callers, was calling, the average scores were very significantly above the 25% hit rate expected by chance. The callers were selected at random, and the subjects made their guesses before answering the call. These positive results were replicated independently at the universities of Amsterdam, Holland, and Freiburg, Germany. Similar telepathic phenomena seem to occur in connection with emails and SMS messages. Experimental tests using all these methods gave significantly above-chance results. Versions of telephone and SMS tests designed to detect precognition, as opposed to telepathy, gave results at chance level, suggesting that the positive results in the telepathy tests were indeed a result of telepathy rather than precognition. Automated telepathy tests using mobile telephones now enable anyone to participate in this research. These forms of telepathy have evolved in connection with modern communication technologies and probably occur because people's intention to call or send a message can be detected telepathically before the call has been made or the message sent.

Can people sense telepathically who is sending them an email before they receive it? Subjects, aged from 12 to 66, registered online with the names and email addresses of 3 senders. A computer selected a sender at random, and asked him to send an email message to the subject via the computer. The computer then asked the subject to guess the sender's name, and delivered the message after receiving the guess. A test consisted of 6 or 9 trials. In a total of 419 trials, including data from incomplete tests, there were 175 hits (41.8%), significantly above the 33.3% chance level (p = .0001). Hit rates in incomplete tests were higher than in complete tests. There was no significant difference between hit rates with male and female subjects. The highest hit rates were with subjects in the 20-29 age group. The effect size in these tests was lower than in previous telephone and email telepathy tests, in spite of the fact that they were unsupervised. One reason may be that the subjects were being asked to guess who had sent them a message several minutes earlier, rather than thinking about them simultaneously.

Objective: To carry out automated experiments to test for telepathy in connection with text messages.

Method: Subjects, aged from 11 to 72, registered online with the names and mobile telephone numbers of 3 senders. A computer selected a sender at random, and asked him to send an SMS message to the subject via the computer. The computer then asked the subject to guess the sender's name, and delivered the message after receiving the guess. A test consisted of 9 trials.

Interactions evaluated: The effects of subjects' sex and age and the effects of delay on guesses.

Main outcome measure: The proportion of correct guesses of the sender's name, compared with the 33.3% mean chance expectation.

Results: In 886 trials there were 336 hits (37.9%), significantly above the 33.3% chance level (p = .001). The hit rate in incomplete tests was 38.4% (p = .03) showing that optional stopping could not explain the positive results. Most tests were unsupervised, which left open the possibility of cheating, but high-scoring subjects were retested under filmed conditions, where no cheating was detected, with 19 hits in 43 trials (44.2%; p = 0.09).

Key words: SMS messages, telepathy, ESP, automated test, internet experiment.

In an automated online telepathy test, each participant had four senders, two actual and two virtual, generated by the computer. In a series of twelve 30-second trials, the computer selected one of the senders at random and asked him to write a message to the subject. After 30 seconds, the participant was asked to guess who had written a message. After the computer had recorded his guess it sent him the message. In a total of 6,000 trials there were 1599 hits (26.7%), significantly above the chance expectation of 25%. In filmed tests the hit rate was very similar. The hit rate with actual senders was higher than with virtual senders, but there was a strong guessing bias in favour of actual senders. When high-scoring subjects were retested, hit rates generally declined, but one subject repeatedly scored above chance.

This paper describes an automated online telepathy test in which each receiver had four senders. In a series of 10 trials the computer picked on of the senders at random and asked her to write a short message to the receiver. At the end of the one-minute trial period, the receiver was asked to guess which sender had written a message, and she received the message only after this guess had been recorded by the computer. The receivers chose their own senders when they registered for the test. If they chose only two or three, the computer supplied virtual senders so that there were four senders altogether. In a total of 1,980 trials there were 581 hits (29%), significantly above the chance expectation of 25% (p = 0.000006). In tests with two real and two virtual senders, there were significantly more hts with real than virtual senders. Receivers had significantly higher hit rates with family members than with non-family members. Cheating seems unlikely, but it could not be ruled out, and for evidential purposes the hit rates can be regarded as suggestive only. Telepathy could provide on possible explanation for the above-chance results, but other forms of ESP could not be eliminated.

This study investigated possible telepathic communication in connection with e-mails. On each trial, there were four potential e-mailers, one of whom was selected at random by the experimenter. One minute before a prearranged time at which the e-mail was to be sent, the participant guessed who would send it. 50 participants (29 women and 21 men) were recruited through an employment web site. Of 552 trials, 235 (43%) guesses were hits, significantly above the chance expectation of 25%. Further tests with 5 participants (4 women, 1 man, ages 16 to 29) were videotaped continuously. On the filmed trials, the 64 hits of 137 (47%) were significantly above chance.

The authors tested whether participants (N = 4) could tell who was calling before answering the telephone. In each trial, participants had 4 potential callers, one of whom was selected at random by the experimenter. Participants were filmed on time-coded videotape throughout the experimental period. When the telephone began ringing, the participants said to the camera whom they thought the caller was and, in many cases, also how confident they felt in their guesses. The callers were usually several miles away, and in some cases thousands of miles away. By guessing at random, there was a 25% chance of success. In a total of 271 trials, there were 122 (45%) correct guesses (p = 10^-12). The 95% confidence limits of this success rate were from 39% to 51%. In most trials, some of the callers were familiar to the participants and others were unfamiliar. With familiar callers there was a success rate of 61% (n = 100; p = 10^-13). With unfamiliar callers the success rate of 20% was not significantly different from chance. When they said they were confident about their guesses, participants were indeed more successful than when they were not confident.

The ability of people to guess who is calling on the telephone has recently been tested experimentally in more than 850 trials. The results were positive and hugely significant statistically. Participants had four potential callers in distant locations. At the beginning of each trial, remote from the participant, the experimenter randomly selected one of the callers by the throw of a die, and asked the chosen caller to ring the participant. When the phone rang, the participant guessed who the caller was before picking up the receiver.

By chance, about 25% of the guesses would have been correct. In fact, on average 42% were correct. The present experiment was an attempt to replicate previous tests, and was filmed for television. The participant and her callers were all sisters, formerly members of the Nolan Sisters band, popular in Britain in the 1980s. We conducted 12 trials in which the participant and her callers were 1 km apart. Six out of 12 guesses (50%) were correct. The results were significant at the p=0.05 level.

Muchas personas afirman saber quien llama antes de atender el teléfono, o haber pensado en alguien sin razón aparente, y la persona luego llama. Llevamos cabo una serie de experimentos para testear si la gente podía o no decirnos realmente quien estaba llamando por teléfono. Cada participante tuvo cuatro posibles "llamadores" potenciales, y cuando el teléfono sonaba se les invitaba a decir quien estaba llamando antes que la otra persona hablara. La probabilidad estadística de éxito se calculó en un 25% de un total de 571 ensayos no videograbados, involucrando a 63 participantes. El resultado global fue del 40% con un 95% de confiabilidad dentro de los límites entre 36 a 45%. El efecto fue altamente significativo (p= 4x10^-16 ). Investigamos subsiguientes pruebas con cuatro participantes bajo condiciones más rigurosas, de las cuales fueron videograbadas las sesiones experimentales, y estas videocintas evaluadas en forma independientemente por un sujeto a "ciegas" de los detalles experimentales. De un total de 271 ensayos videograbados, el rango de éxito fue de 45% (p= 1x10^-12). El nivel de confiabilidad fue de un 95% dentro de un rango de éxito de entre el 39% al 51%. Los participantes tuvieron mucho más éxito con llamadas de familiares que con llamadas de extraños y esta diferencia fue estadísticamente significativa. No hubo efecto de declinación con la distancia, aún cuando algunos llamadores se encontraban a 18.000 km. de distancia. Estos efectos parecen ser inexplicables en términos de habiliades o fraude y produjo una fuerte evidencia de la realidad de la telepatía telefónica.

Many people claim to have known who was calling before they picked up the telephone, or to have thought about someone for no apparent reason, and that person then called. We carried out a series of experiments to test whether or not people really could tell who was telephoning. Each participant had four potential callers, and when the telephone rang had to guess who was calling before the other person spoke. By chance the success rate would have been 25%. In a total of 571 non-videotaped trials, involving 63 participants, the overall success rate was 40%, with 95% confidence limits from 36 to 45%. This effect was highly significant statistically (p= 4x10^-16). We then carried out further trials with four participants under more rigorous conditions in which they were videotaped throughout the experimental sessions, and the videotapes were evaluated independently by a person blind to the experimental details. In a total of 271 videotaped trials the success rate was 45% (p= 1x10^-12). The 95% confidence limits of this success rate were from 39% to 51%. Participants were much more successful with familiar callers than unfamiliar callers, and this difference was highly significant statistically. There was no decline with distance, even when callers were 18.000 km. away. These effects do not seem to be explicable in terms of artefacts or cheating and provide strong evidence for the reality of telephone telepathy.

Many people claim to have known who was calling before they picked up the telephone, or to have thought about someone for no apparent reason, who then called. We carried out a series of experiments to test whether or not people really could tell who was telephoning. Each participant had four potential callers, and when the telephone rang had to guess who was calling before the other person spoke. By chance the success rate would have been 25%. In a total of 571 trials, involving 63 participants, the overall success rate was 40%, with 95% confidence limits from 36 to 45%. This effect was hugely significant statistically (p = 4 x 10^-16). We obtained similar positive effects when the calls were made at randomly chosen times, and when the calls were made at fixed times known to the subject in advance. With 37 participants, we compared the success rates with familiar and unfamiliar callers and found a striking difference. With familiar callers, 53% of the guesses were correct (n = 190; p = 1 x 10^-16). With unfamiliar callers, only 25% of the guesses were correct, exactly at the chance level. This difference between the responses with familiar and unfamiliar callers was highly significant (p = 3 x 10^-7). We also investigated the effects of distance between the callers and participants. With overseas callers at least 1,000 miles away, the success rate was 65% (n = 43; p = 3 x 10^-8). With callers in Britain, the success rate was lower (35%). In most cases, the overseas callers were people to whom the participants were closely bonded. For the successful identification of callers, emotional closeness seemed to be more important than physical proximity.

Some nursing mothers claim that when they are away from their baby they often know when their baby needs them because their milk lets down. Some are convinced that this response is telepathic. In order to find out more about this phenomenon, 100 mothers who had recently had babies were surveyed and asked a series of questions about their experiences when breastfeeding. 62% had experienced milk let-down when away from their babies and 16% had noticed that this seemed to coincide with their baby needing them. Most of these women breastfed their babies for more than six months. In addition, 3 women said they had felt there was something wrong with their baby when they were away from home, and found that it was indeed in distress because of a fall or other accident, and 5 women commented that they often woke up shortly before their baby needed them in the night.

200 randomly-selected people were surveyed in Santa Cruz County, California to investigate the frequency and nature of anticipations of telephone calls. 78% of the people surveyed said that they have had the experience of telephoning someone who said that they were just thinking about telephoning them. 47% of the respondents said that they had had the experience of knowing who was calling them when the phone rang without any possible cue. 68% of those surveyed said that they had thought about a person that they haven't seen for a while, who had then telephoned them that same day. A higher proportion of women than men gave positive answers to these questions. These results are in general agreement with two previous surveys in England, although there were several significant differences, which we discuss. These surveys reveal that seemingly telepathic experiences in connection with telephone calls are remarkably common. We suggest ways that this phenomenon can be investigated empirically.

Many people claim to have thought about a particular person who then calls them on the telephone. Through informal surveys I have found that seemingly telepathic telephone calls are common. Two telephone surveys were carried out in London and Bury to investigate the frequency of these experiences in a random sample of the population. In both surveys, half the respondents said they had felt that someone was about to telephone them just before they did. In Bury, 45 per cent of the respondents said they had thought about a person they had not seen for a while who then telephoned the same day, and two thirds of the Bury respondents said they had telephoned people who said they were just thinking about telephoning them. In Bury, 37 per cent of respondents who said they had know in advance who was calling without any possible clue said this happened often. In both surveys significantly more women than men gave positive responses, and in both surveys more pet owners than people without pets gave positive responses. In London significantly more people claimed to have anticipated telephone calls that to have had psychic experiences. Telepathic telephone calls may be one of the commonest kinds of psychic experience in the modern world, and I suggest ways in which they can be investigated empirically.

Many people report that they know in advance who is on the phone when the telephone is ringing. Sheldrake and Smart [1, 2] conducted experiments where participants had to determine which one of four possible callers is on the phone while the telephone was still ringing. They report highly significant hit rates that cannot be explained by conventional theories.

We attempted to replicate these findings in a series of three experiments. In study one, 21 participants were asked to identify the callers of 20 phone calls each. Overall 26.7 % were identified correctly (mean chance expectation 25%, ns). In a second study a pre-selection test was introduced in a different experimental setting. Eight participants identified 30% of the calls correctly (p = .15). However one of the participants recognized 10 out of 20 calls correctly (p = .014). We conducted a third study with only this participant. In an additional 60 trials she could identify 24 callers correctly (p = .007). We conclude that we could not find any anomalous cognition effect in self-selected samples. But our data also strongly suggest that there are a few participants who are able to score reliably and repeatedly above chance.

Can we guess who is calling us on the phone before picking up, and does local sidereal time (LST) affect how often we guess right? Reviews of anomalous cognition studies have shown that effect sizes are highest around 13.30 LST (Spottiswoode, 1997). A post-hoc analysis of telephone telepathy data of Sheldrake (2003) also showed a peak at that time. LST (peak or non-peak) was an independent variable in our prospective telephone telepathy study. Six women who indicated they often experienced telephone telepathy were selected to participate. Each participant chose four close friends or relatives to act as callers. All completed a total of 36 trials; six sessions of six trials each, three sessions at peak time (between 8.00 and 9.00 local time) and three at non-peak time (between 17.30 and 18.30 local time). One of the experimenters was at the participant's home during the sessions. The experimenter made sure no irregular communication was going on and logged times of the calls and responses of the participant. At a different location another experimenter used a dice to select a caller about five minutes before the scheduled trial. Then he or she contacted the caller who was asked to call the participant in five minutes and to concentrate his or her thoughts on the participant for the last two minutes before the call was made. When the phone rang at the participant's home, the participant guessed who she thought was calling before picking up. Analyses show a significant over-all scoring rate of 29.4% (p = .05). Almost all of this effect originates from the sessions at peak time with a scoring rate of 34.6%. Exploratory analyses show that a stronger emotional bond between particpant and caller is associated with a higher hitrate. It is concluded that results provide tentative support for the hypothesis that Local Sidereal Time is related to a phenomenon like telephone telepathy. In addition, the results are in support of the existence of telephone telepathy. Other explanations of the anomalous effect cannot be ruled out, such as precognition, retro psychokinesis by the experimenter or the participant so the dice throw would coincide with the particular caller the participant would guess, or clairvoyance of the dice throws. Future studies should aim at teasing apart the supposed effects of LST and local time on 'telephone telepathy.'

Part 1: Is it Real or Illusory?
Part 2: Its Implications for Theories of Vision
The Non-Visual Detection of Staring - Response to Commentators

The complete edition, entitled Sheldrake and His Critics: The Sense of Being Glared At is available in paperback.

In 1981 Rupert Sheldrake outraged the scientific establishment with his hypothesis of morphic resonance. Subsequently he devoted his research to pioneering science, winning popular acclaim and continued establishment opprobium with a series of ground-breaking works. In this special edition of JCS, Rupert summarises his case for the 'non-visual detection of staring'. His claims are scrutinised by fourteen critics, to whom Rupert then responds. Anthony Freeman, in his editorial introduction, explores the concept of "heresy" in science and in religion and asks why it provokes such hostility.

In previous research on the sense of being stared at participants worked in pairs, with the starer behind the staree. In a series of 20 randomized trials, the starer looked or did not look at the staree, who had to guess "looking" or "not looking". We here describe an automated, internet-based version of this standard staring experiment. In 498 tests, each with 20 trials, the computer gave an automatic sound signal to indicate when each trial began. The average hit rate was 53.0% (p <1x10^-6); 268 participants scored above the chance level of 10 out of 20, 150 below, and 80 at the chance level. There was no significant difference between male and female starees, and little effect of starees' age. The highest hit rates were with parent-child participants. Hit rates were significantly higher when starees received trial-by-trial feedback, but there was no increase in the second half of the test compared with the first. Although these tests were unsupervised, the results replicated many of the features of previous tests and illustrate the potential for carrying out research through the internet, enabling widespread participation.

Simple experiments on the sense of being stared at have given repeatable, positive results that are highly significant statistically. In these experiments, people work in pairs. The staree sits with his or her back to the starer, who either looks at the back of the staree's neck, or looks away, in a random sequence. In each trial, the staree has to guess whether or not the starer is looking. However, when Marks & Colwell (2001) and Lobach & Bierman (2004) conducted tests of this kind, some of their experiments gave results not significantly different from chance, and they attempted to explain the positive results in staring tests as artifacts. Their hypotheses predict that positive scores should arise only in trials with feedback, only in trials with one particular kind of randomization, and that scores should increase towards the end of the experimental session. I have examined the data from the first and second halves of more than 19,000 trials to test these predictions. Both with and without feedback, and also with different randomization methods, the scores were positive and statistically significant in both the first and the second halves of tests. With feedback there was a small increase in scores in the second halves, but this was not statistically significant. Without feedback, there was a tendency for the scores to decline. In a trial-by-trial analysis of one large-scale experiment, the highest hit rate occurred in the very first trial for starees who were about to receive feedback, before any feedback had actually been given! Thus the beneficial effect of feedback may not depend so much on the feedback itself as the state of mind of the participants.

The sense of being stared at, or scopesthesia, was investigated experimentally with participants working in pairs. Two participants were tested repeatedly and the effect of attentional transition was investigated. In some tests, in the pre-trial period the starer stared at the staree, who was blindfolded, and in others the starer did not stare during the pre-trial period. Their overall hit rate in these attentional transition tests was 52.8% (2,800 trials; p=0.002), but there was no significant difference in hit rates between the two kinds of test. Participants were given trial-by-trial feedback, so if there was any learning, there should have been a progressive increase in hit rates. This did not happen. The participants also took part in a control tests in which there was no staring at all. In these tests hit rates were at chance levels, indicating that other forms of ESP, such as telepathy and clairvoyance, could not account for the results in scopesthesia tests. There were only 3 recording errors in 2,800 trials (0.1%), and two of these cancelled out, leaving a net error rate of 0.04%.

The sense of being stared at from behind can be investigated by means of simple experiments in which subjects and lookers work in pairs, with the looker sitting behind the subject. In a random sequence of trials the looker either looks at the back of the subject, or looks away and thinks of something else. In each trial the subject guesses whether or not he or she is being looked at. There is a 50% probability of getting it right by chance. More than 15,000 trials have already been conducted, involving more than 700 subjects, with extremely significant excess of correct over incorrect guesses (Sheldrake, 1999), indicating that people really can tell when they are being looked at from behind. In this paper I discuss possible artifacts that could have affected these results and describe the results of experiments carried out in a school in London in which I investigated the effects of blindfolding subjects and giving them feedback about whether their guesses were correct or not. Blindfolding and feedback had no significant effects. Under all conditions the scores in looking trials were positive and statistically significant, and in not-looking trials at chance levels. I also describe the results of a series of experiments carried out in schools in Ireland with blindfolded subjects who were not given feedback. The significant positive scores in these experiments confirmed that the feeling of being stared at from behind does not depend on visual clues, nor does it depend on the subjects knowing if their guesses are right or wrong.

Two recent articles in the Skeptical Inquirer have claimed that the feeling of being stared at is an illusion. Both have attempted to refute my own experimental research on the subject, which indicates that many people do indeed have an unexplained ability to detect stares.

A variety of surveys have shown that most people believe they can feel unseen stares (Sheldrake 1994). In his article "Can we tell when someone is staring at us?" (March/April 2000 SI) Robert A. Baker, a CSICOP Fellow, dismissed this belief as false. "Skeptics.... believe that it is nothing more than a superstition and/or a response to subtle signals from the environment." (Baker 2000, p. 40). He claimed to provide empirical evidence to support his presuppositions.

Simple experiments to test whether or not people can tell when they are being stared at from behind were carried out in schools in Germany and the United States. Lookers and subjects worked in pairs, with the lookers sitting behind the subjects. In a series of trials the lookers either looked or did not look at the subjects in a random sequence determined by tossing a coin. In each trial, the subjects guessed whether or not they were being looked at. The results show an overall positive effect, with 56.9% correct guesses as opposed to 50% expected by chance. 97 of the subjects were right more often than they were wrong, and 42 were wrong more often than they were right. This positive effect was highly significant statistically (p=3x10^-6). The data showed a consistent pattern. There was a positive effect when the subjects were being looked at, while the guesses were not significantly different from chance when they were not being looked at. In one school in Germany where sensitive subjects were tested repeatedly, 71.2% of the guesses were correct, and two students were right about 90% of the time. Possible sources of artefacts in these experiments are examined, and the implications of the results are discussed.

Simple experiments to test whether or not people can tell when they are being stared at from behind were carried out in schools in Germany and the United States. Lookers and subjects worked in pairs, with the lookers sitting behind the subjects. In a series of trials the lookers either looked or did not look at the subjects in a random sequence determined by tossing a coin. In each trial, the subjects guessed whether or not they were being looked at. The results show an overall positive effect, with 56.9% correct guesses as opposed to 50% expected by chance. 97 of the subjects were right more often than they were wrong, and 42 were wrong more often than they were right. This positive effect was highly significant statistically (p=3x10^-6). The data showed a consistent pattern. There was a positive effect when the subjects were being looked at, while the guesses were not significantly different from chance when they were not being looked at. In one school in Germany where sensitive subjects were tested repeatedly, 71.2% of the guesses were correct, and two students were right about 90% of the time. Possible sources of artefacts in these experiments are examined, and the implications of the results are discussed.

The "sense of being stared at" can be investigated by means of simple experiments in which subjects and lookers work in pairs, with the looker sitting behind the subject. In a random sequence of trials, the looker either looks at the back of the subject, or looks away and thought of something else. More than 15,000 trials have already been conducted, involving more than 700 subjects, with an extremely significant excess of correct over incorrect guesses (Sheldrake [1999]). This effect was still apparent in experiments in which subjects were blindfolded and given no feedback, showing it did not depend on visual clues, nor on the subjects knowing if their guesses were right or wrong (Sheldrake [2000]). In this paper I describe experiments I conducted in schools in England in which the subjects were not only blindfolded and given no feedback, but looked at through closed windows. There was again a very significant excess of correct over incorrect guesses (p<0.004). At my request, teachers in Canada, Germany and the United States carried out similar experiments and found an even more significant positive effect than in my own experiments (p< 0.0002). The fact that positive results were still obtained when visual clues had been effectively eliminated by blindfolds, and auditory and olfactory clues by closed windows, implies that the sense of being stared at does not depend on the known senses. I conclude that peoples' ability to know when they are being looked at depends on an influence at present unknown to science.

The feeling of being stared from behind is well known all over the world, and most people claim to have experienced it themselves. There have been surprisingly few empirical investigations of this phenomenon. I describe a simple experimental procedure with subjects and lookers working in pairs. In a random sequence of trials, the looker either looked at the back of the subject, or looked away and thought of something else. Such experiments showed a very significant excess of correct over incorrect guesses. When subjects were being looked at, they guessed correctly about 60% of the time, whereas in control trials, when they were not being looked at, their guesses were close to the chance level of 50%. The same pattern of results was found in my own experiments with adult subjects, with two different procedures: in experiments conducted in schools in Connecticut, USA: in experiments conducted by volunteers all around the world; and in a previous series of experiments in schools in Germany and the USA. All these sets of data showed a highly significant effect. Taken together they showed that in looking trials, 427 people were more often right than wrong, as opposed to 157 who were more often wrong than right. This difference is extremely significant (p<1x10-25). In the control trials, there was no significant difference between the number of people who were more often right than wrong (294) and more often wrong than right (287). These results suggest that the feeling of being looked at from behind is a real phenomenon that depends on factors as yet unknown to science. Non-human animals may also share this kind of sensitivity, which may be of evolutionary sugnificance in the relationships between predators and prey.

Findings in parapsychology suggest an effect of distant intentionality. Two laboratory set-ups explored this topic by measuring the effect of a distant intention on psychophysiological variables. The 'Direct Mental Interaction in Living Systems' experiment investigates the effect of various intentions on the electrodermal activity of a remote subject. The 'Remote Staring' experiment examines whether gazing by an observer covaries with the electrodermal activity of the person being observed. Two meta-analyses were conducted. A small significant effect size (d =.11, p = .001) was found in 36 studies on 'direct mental interaction', while a best-evidence-synthesis of 7 studies yielded d = .05 (p = .50). In 15 remote staring studies a mean effect size of d = 0.13 (p = .01) was obtained. It is concluded that there are hints of an effect, but also a shortage of independent replications and theoretical concepts.

The standing wave patterns formed on the surface of a vertically oscillated fluid enclosed by a container have long been a subject of fascination, and are known as Faraday waves. In circular containers, stable, radially symmetrical Faraday wave-patterns are resonant phenomena, and occur at the vibrational modes where whole numbers of waves fit exactly onto the surface of the fluid sample. These phenomena make excellent systems for the study of pattern formation and complex nonlinear dynamics. We provide a systematic exploration of variables that affect Faraday wave pattern formation on water in vertical-walled circular containers including amplitude, frequency, volume (or depth), temperature, and atmospheric pressure. In addition, we developed a novel method for the quantification of the time taken for patterns to reach full expression following the onset of excitation. The excitation frequency and diameter of the container were the variables that most strongly affected pattern morphology. Amplitude affected the degree to which Faraday wave patterns were expressed but did not affect pattern morphology. Volume (depth) and temperature did not affect overall pattern morphology but in some cases altered the time taken for patterns to form. We discuss our findings in light of René Thom’s catastrophe theory, and the framework of attractors and basins of attraction. We suggest that Faraday wave phenomena represent a convenient and tractable analogue model system for the study of morphogenesis and vibrational modal phenomena in dynamical systems in general, examples of which abound in physical and biological systems.

Context
Joint attention is the shared focus of two or more individuals on the same object. Sensory cues, such as detecting the direction of another person׳s gaze, play a major role in establishing joint attention. It may also involve a kind of mental resonance that might be felt by the people involved.

Objective
The aim of this study was to find out whether people could feel when another person was looking at the same picture at the same time, even when the participants were many miles apart.

Method
Participants registered online with their names and e-mail addresses, and worked in pairs. After they both logged on for the test they were simultaneously shown one of two photographs, with a 0.5 probability of seeing the same picture. After 20 s they were asked if their partner was looking at the same picture or not. After both had registered their guess, the next trial began, with a different pair of pictures. The main outcome measure was the proportion of correct guesses, compared with the 50% mean chance expectation. This test was symmetrical in that all participants were both “senders” and “receivers.”

Results
In the first experiment, with 11,160 trials, the hit rate was 52.8% (P < 1 × 10−6); in the second experiment with 2720 trials, 51.3% (P = .09). The third experiment involved music as well as pictures, and with 8860 trials, the hit rate was 51.9% (P = .0003). Some partners were more than 1000 miles apart, but there were no significant effect of distance. Participants who received immediate feedback about whether their guess was right or wrong did not score significantly better than those without feedback.

This study investigated whether people could tell when another person was looking at teh same object.participants looking directly at the same object. Participants worked in pairs. They were separated by a wall in such a way that they could not see each other, but both could see a target object such as an apple. Tests consisted of 20 trials, each lasting about 10 seconds. One of the participants (the ‘ looker’) either looked at the object, or did not look, in a random sequence, and the other participant (the ‘guesser’) had to guess whether or not the other person was looking at the object. Altogether there were 310 tests with 6,200 trials. The total number of hits was 3,255 (52.5%), significantly above the chance level of 50% (p = 0.00003).

Why are many schoolchildren still told to write up their science reports in the passive, as though experiments happened of their own accord? Many scientists abandoned this convention years ago. Watson and Crick's famous paper on the structure of DNA in Nature was in the active voice in 1953.

In scientific research, as in everyday life, our beliefs and biases often influence how we observe and interpret the world. In experimental psychology and clinical research, this problem is widely recognized, which is why experiments in these subjects are often carried out under blind or double-blind conditions. There is solid experimental evidence that experimenters' attitudes and expectations can influence the outcome of experiments.

Most scientific journals accept papers in the active voice and some, including Nature, positively encourage it. When I surveyed the current issues of 55 journals in the physical and biological sciences I found only two that still required contributors to use the passive.

In everyday life, as in scientific research, "our beliefs, desires and expectations can influence, often subconsciously, how we observe and interpret things", as a recent article in the Skeptical Inquirer expressed it.(note 1) In experimental psychology and clinical research, these principles are widely recognized, which is why experiments in these subjects are often carried out under blind or double-blind conditions. There is overwhelming experimental evidence that experimenters' attitudes and expectations can indeed influence the outcome of experiments.

A survey of recent papers published in a range of scientific journals showed that the used of blind methodologies is very rare in the so-called hard sciences. In the physical sciences, no blind experiments were found among the 237 papers reviewed. In the biological sciences, there were 7 blind experiments out of 914 (0.8%). There was a higher proportion in the medical sciences, 6 out of 102 (5.9%), and in psychology and animal behaviour, 7 out of 143 (4.9%). By far the highest proportion (85.2%) was in parapsychology. A survey of science departments in 11 British Universities showed that blind methodologies are neither used nor taught in 22 out of 23 physics and chemistry departments, or in 14 out of 16 biochemistry and molecular biology departments. By contrast, blind methodologies are sometimes practised and taught in 4 out of 8 genetics departments, and in 6 out of 8 physiology departments. I propose a simple procedure that could be used to detect possible experimenter effects in any branch of science, by comparing the results of a given experiment conducted both under open and blind conditions.

Probably most skeptics would agree with Michael Mussachia (SI Nov/Dec 1995) that "our beliefs, desires and expectations can influence, often subconsciously, how we observe and interpret things". In psychology and clinical medicine these principles are widely recognized, which is why experiments in these subjects are often carried out under blind or double-blind conditions.

Controversial biologist Rupert Sheldrake has recently published surveys suggesting that much of the current research in science may suffer from an important methodological problem that could seriously challenge the validity of many scientific findings. This article sets in motion a project designed to assess the impact of Sheldrake's provocative findings.

Short-duration pigeonpea can give up to three harvests in environments with mild winters (eg. minimum temperature above 10*C) such as those prevailing in peninsular India (Sharma, Saxena & Green, 1978; Chauhan, Venkataratnam & Sheldrake, 1984). This is mainly due to the short time (about 120 days) taken to produce the first flush, and the strong perennial character of pigeonpea. The seed yield of short-duration pigeonpea in this multiple-harvest system may reach 5.2t/ha (Chauhan et al. 1984).

Venkataratnam & Sheldrake (1985) found that the yield of the second harvest of medium-duration pigeonpea was significantly influenced by the method of harvesting of the first flush. The lower the plants were cut, the smaller were the second-harvest yields. A positive relationship between the height at which the stem was cut and success of ratooning was also reported by Suarez & Herreara (1971). Tayo (1985), however, found that in the lowland tropics, plants of a dwarf pigeonpea variety ratooned at 0.3 m had better growth and yield than hand-picked plants; ratooning at 0.6 m height was intermediate. Information on the effect of different harvest methods on yield of short-duration pigeonpea in subtropical, semi-arid environments is not available. The objective of this study was to obtain this information.

Environmental and cultural factors that may limit the yield of short-duration pigeonpea were investigated over three seasons. Plants in the peninsular Indian environment at Patancheru grew less and produced less dry matter by first-flush maturity than at Hisar, a location in northern India where the environment is considered favourable for the growth of short-duration pigeonpea. However, with a similar sowing date in June, the mean seed yields of three genotypes, ICPL4, ICPL81 and ICPL87, were very similar, at about 2-3t/ha, in both environments. This was mainly due to the higher ratio of grain to above-ground dry matter at Patancheru. In addition to the first harvest, all genotypes showed a potential for two more harvests owing to the warm winters at Patancheru. The potential for multiple harvests was particularly high in ICPL 87, which yielded 5.2t/ha from three harvests in 1982-3, 3.6t/ha from two harvests in 1983-4, and 4.1 t/ha from three harvests in 1984-5. The optimum plant population density at Patancheru was 25-35 plants/m2 for ICPL 87, but was higher for the other two genotypes.

At Patancheru, the total dry-matter and seed yield of first and subsequent harvests were significantly reduced by delaying sowing beyond June. Generally, the second-and the third-harvest yields were lower on vertisol than on alfisol under both irrigated and unirrigated conditions.

The total yield of ICPL 87 from two harvests was far higher than that of a well-adapted medium-duration genotype BDN 1, grown over a similar period. The yield advantage was greater on the alfisol because of the better multiple harvest potential of this soil. The results of this study demonstrate that properly managed short-duration genotypes of pigeonpea may have considerable potential for increased yield from multiple harvests in environments where winters are warm enough to merit continued growth.

The feasibility of growing pigeonpea [Cajanus cajan (LInn.) Millsp.] as a perennial crop was investigated during 1980-82. The medium-duration pigeonpea genotype 'ICP 1-6', sown in the post-rainy season at a population of 30 plants/m2, was allowed to perennate for 18 months, during which it produced 3 flushes of pods at 5,15 and 18 months after sowing. There was a substantial plant mortality after the first-flush harvest, but due to the high-sowing rate many plants survived and regenerated to form a closed canopy in the following rainy season. The mean yield of 2 seasons was 0.5 tonne/ha in the first flush, 1 tonne/ha in the second and 0.05 tonne/ha in the third. The yield from the second flush was obtained without weeding or insecticide spray and was comparable to that of the rainfed crop of medium-duration genotypes. Considerable leaf fall also occurred, which contributed 40kg N/ha to the soil. The yield from the third flush was very low to warrant continuation of the crop for another 3-4 months after the second-flush crop. At this harvest the mean firewood (air-dried stem) yield was 3.5 tonnes/ha. The system has good potential in the wet rainy season fallows in peninsular India, as it enables pigeonpea after the rainy season with little efforts and few inputs.

In Peninsular India medium duration pigeonpeas (Cajanus cajan) are normally sown soon after the onset of the monsoon, in June or July; they mature around December, when they are usually cut down and removed from the field. However, if they are harvested by ratooning or by picking the pods, the plants go on to produce a second flush of pods, which matures around March. In experiments conducted in four growing seasons at ICRISAT Center, second harvest yields were usually greater for non-ratooned than ratooned plants, and in experiments conducted on Vertisols they were greater for the plants ratooned high up in the plant than for those cut closer to the ground. Second harvest yields of non-ratooned plants without irrigation on Alfisols were on average 66% of the first harvest yields, but on Vertisols only 37%, in spite of the greater water-holding capacity of the latter. On Alfisols second harvest yields were approximately doubled by a single irrigation, but there was less response to irrigation on Vertisols. The poorer second harvest yields on Vertisols may have been due to the damaging effects of soil cracking on the root system of the plants. In non-ratooned plants from which the first and second flushes of pods were harvested together, yields were less than the total yield obtained from non-ratooned plants in two harvests, even though the yield loss, mainly due to pod shattering, was as little as 4% in one year. The taking of second harvests from pigeonpeas grown on Alfisols may have considerable potential as a method of obtaining additional yield for little extra cost.

During the 3 years 1974-77 we studied the anatomy of most of the tissues and organs of the pigeonpea and, in the course of this work, have built up a collection of permanent microscope slides. These are retained in the Anatomy Laboratory at ICRISAT as a reference collection and may be consulted by anyone who is interested.

This report contains a brief and preliminary description of pigeonpea anatomy. We have studied the anatomy of several different cultivars; unless otherwise indicated, the following general descriptions apply to all cultivars investigated. We have not noticed any striking qualitative anatomical differences among cultivars; nodoubt quantitative differences exist, but these are difficult to establish with anatomical methods involving very small samples.

Many of the features of the anatomy of the pigeonpea are similar to those of other dicotyledonous plants, described in standard textbooks of anatomy. We have not attempted to duplicate these descriptions. Some aspects of the anatomy of the pigeonpea have been covered in detail by Dr. P. Venkateshwara Rao in his Ph.D. thesis under reference (nodate). A copy of this thesis is available in the ICRISAT library.

Larger seeds of chickpea (Cicer arietinum) and pigeonpea (Cajanus cajan) gave rise to larger seedlings than did smaller seeds. When approximately half the cotyledonary reserves from pigeonpea seeds were removed, seedling weight was reduced to about half of the controls, suggesting that seedling growth was related to the reserve material in the seeds. Seed-grading had no significant effect on the yield of either of these crops grown on a Vertisol and on Alfisol in Andhra Pradesh, or on an Entisol in Haryana or in the Lahaul valley of the western Himalayas. Seeds harvested from pigeonpea grown from larger seeds were significantly heavier than those from plants derived from small seeds, probably because of the genetic heterogeneity of the varieties.

The influence of seed size on seedling growth of pigeonpea [Cajanus cajan (Linn.) Millsp.] and chickpea (Cicer arietinum Linn.) was investigated to predict probable consequnces of selection for seed size in breeding programmes. Seeds of 20 pigeionpea varieties with 100-seed weights of 4.5 to 22 g and 23 chickpea varieties with 100-seed weights of 5 to 32 g were sown in the field, and the leaf area and dry weight of the seedlings were measured at intervals up to 56 and 30 days respectively. In both species there was a close linear relationship between 100-seed weight and seedling weight (r = 0.77* for 14-day-old pideonpea; r = 0.82** for 16-day-old chickpea). In pigeonpea the relationship was even closer (r = 0.95**) when varieties having 100-seed weights of over 15 g were excluded. With the advancement of growth the closeness of these relationships declined. Large-seeded varieties of these crops produce larger and more vigorous seedlings, which will have an advantage in stand establishment under adverse conditions.

Pod photosynthesis is known to contribute to seed filling in a number of legume crops, and may also be of importance in chickpeas (Cicer arietium L.), which have green pods possessing stomata. Although the pods of chickpeas are borne in the leaf axils, they generally hang below the leaves and are consequently more or less shaded; but a few lines have recently been identified in which the pods are borne above the leaves. This *exposed pod* character could be incorporated into new cultivars by breeding if it were shown to be of advantage. The effect on yield and yield components of exposing pods of normal cultivars was investigated in field experiments at three locations in India: at Hyderabad and Hissar during the winter season, and in the Lahaul valley in the Himalayas during the summer season. A significant effect of pod exposure on yield or yield components was not observed in any of the experiments, except at Hissar where a slight but significant increase in 100-seed weight was noted. The *exposed pod* character is unlikely to be of use in breeding for higher yield potentials.

Genotypic differences exist in the sensitivity of cultivars of chickpea to iron deficiency. Sensitive cultivars exhibited typical iron deficiency symptoms when grown on calcareous soils with high pH. FeSO4 sprays (0.5%) corrected deficiency symptoms and increased yields by up to 50% in cultivars inefficient in iron utilization, but gave no increase in cultivars that were efficient.

Research conducted by ICRISAT at Hissar (representative of N. India) and Hyderabad (representative of peninsular India) on the growth, pod development, yield components, nutrient uptake, source/sink relationships, fertilizer and irrigation response, effects of intercropping, apex removal, row orientation, sowing pattern, plant density and seed size, cv. plasticity and cv. differences in germination, Fe chlorosis, salinity tolerance, heat tolerance and water stress response of chickpea is reviewed.

In chickpeas (Cicer arietinum) flowering and pod development proceed acropetally. In plants grown under normal field conditions at Hyderabad, in peninsular India, and at Hissar in north India, at successively apical nodes of the branches there was a decline in pod number per node, weight per pod, seed number per pod and/or weight per seed. The percentage of nitrogen in the seeds was the same in earlier- and later-formed pods at Hyderabad; at Hissar the later-formed seeds contained a higher percentage. Earlier- and later-formed flowers contained similar numbers of ovules. The decline in seed number and/or weight per seed in the later-formed pods of 28 out of 29 cultivars indicated that pod-filling was limited by the supply of assimilates or other nutrients. By contrast, in one exceptionally small-seeded cultivar there was no decline in the number or weight of seeds in later-formed pods, indicating that yield was limited by 'sink' size.

On branches of indeterminate cultivars of pigeonpea, flowering begins at the basal nodes and proceeds acropetally; in morphologically determinate cultivars, flowering begins on the apical racemes and proceeds basipetally. In cultivars of both types, within the racemes flowering proceeds acropetally. Under normal conditions more pods are set from earlier-formed flowers than from later-formed flowers, many of which are shed. Consequently the earlier-formed pods are found at the more basal nodes of racemes, and in indeterminate cultivars at the more basal nodes on the branches. The average weight of earlier- and later-formed pods, collected from the basal and apical nodes of the racemes or of the branches, was similar; so was the number of seeds per pod, the weight per seed and the nitrogen content of the seeds. This pattern differs from that found in most herbaceous legumes, where later-formed pods are smaller, and indicates that pigeonpeas set fewer pods than they are capable of filling. This behaviour may be related to the intrinsically perennial nature of pigeonpeas. The comparison of the weights of earlier-and later-formed pods could provide a simple screening procedure for identifying plants with an annual nature among existing cultivars or in breeders' lines.

In field experiments carried out at Hyderabad, India with early and medium-duration cultivars of Cajanus cajan sown at the normal time, in July, removal of all flowers and young pods for up to 5 wk had little or no effect on final yield. The flowering period of the deflowered plants was extended and their senescence delayed. The plants compensated for the loss of earlier-formed flowers by setting pods from later-formed flowers; there was relatively little effect of the deflowering treatments on the number of seeds per pod or weight per seed. The plants were also able to compensate for the repeated removal of all flowers and young pods from alternate nodes by setting more pods at the other nodes.

The removal of flowers from pigeonpeas grown as a winter crop resulted in yield reductions roughly proportional to the length of the deflowering period, probably because maturation of these plants was delayed and occurred under increasingly unfavourable conditions as the weather became hotter.

The growth and development of two early (Pusa ageti and T-21) and three medium- duration (ST-1, ICP-1 and HY-3C) cultivars of pigeonpea (Cajanus cajan) were compared at Hyderabad, India, in 1974 and 1975; in 1976 cv. ICP-1 was studied. The pigeonpeas were grown on a Vertisol and on an Alfisol. The crop growth rate in the first 2 months was low. The maximum rate of 171 kg/ha/day was found in the fourth month of growth of cv.ICP-1 on Alfisol. The early culitvars, one of which (cv. Pusa ageti) was morphologically determinate, and the other (cv. T-21) indeterminate, did not differ in the proportion of dry matter partitioned into seeds. The mean dry weight of the above- ground parts of the medium cultivars on Vertisol in 1975 was 8.45 t/ha, including 2.23 t/ha of fallen plant material. The mean harvest index (ratio of grain dry weight to total plant dry weight) of these cultivars was 0.24 excluding fallen material and 0.17 taking fallen material into account. Starch reserves were present in the stems during the vegetative phase, but disappeared during the reproductive phase. In 1974 the maximum leaf-area index on Vertisol was 3 and on Alfisol 12.7. The net assimilation rate tended to decline throughout the growth period, but in the medium cultivars increased at the end of the reproductive phase, probably because of photosynthesis in pods walls and stems.

In 1974 and 1975 the growth of roots and distribution of nodules in Vertisol was investigated by means of soil cores. Roots extended below 150 cm and root growth continued during the reproductive phase. Most nodules were found within the first 30 cm of soil, but some were found below 120 cm. In cv. T-21, grown in brick chambers 150 cm deep, at the time of harvest about three-quarters of the mass of the roots was found in the first 30 cm, and the shoot:root ratio was around 4:1.

In 1975 the mean uptake of nitrogen by the medium cultivars on Vertisol was 120 kg/ha, including 34 kg/ha in fallen material. In 1976 the uptake of nitrogen by cv. ICP-1 was 89 kg/ha on Vertisol and 79 kg/ha on Alfisol, including 32 and 23 kg/ha respectively in fallen material. Nitrogen uptake continued throughout the growing period. The percentage of nitrogen in stems and leaves declined as the plants developed and there was a net remobilization of nitrogen from these organs. The pattern of uptake and remobilization of phosphorus resembled that of nitrogen. In 1976 the total uptake of phosphorus by cv. ICP-1 on Vertisol was 5.8 kg/ha and on Alfisol 5.0 kg/ha.

The relatively low yields of pigeonpeas result from a restricted partitioning of dry matter into pods, which may be related to the plants' perennial nature.

In pigeonpeas (Cajanus cajan), most flowers are shed without setting pods. Pod-set is reduced by shading, defoliation and the presence of already developing pods, probably because of the reduced availability of assimilates or other nutrients. In pigeonpeas, unlike most leguminous crops, the average weight per pod of earlier and later formed pods is the same; this indicates that pod-filling is not limited by nutrient supply. Pod-set seems to be controlled in such a way that fewer pods develop than the plants are capable of filling. These processes can be represented by a simple working model, in which the assimilate supply corresponds to water in a reservoir, the axis of a branch or a raceme to a horizontal tube connected to the reservoir, and pods to containers of limited volume at a lower level; the connecting tubes between the axis and the 'pods' have an ascending limb, shorter than the descending limb to the pods, creating a siphon. 'Pods' can 'set' only when the level of water in the reservoir is higher than the threshold of the siphon; during the filling of earlier-set 'pods', the setting of other 'pods' is inhibited by the reduction of pressure within the axis. This model may provide a crude representation of mass flow within the phloem from sources to sinks; it also illustrates some of the hydrodynamical factors involved in competition among sinks.

Pigeonpeas (Cajanus cajan) are normally sown in June or July in India, at the beginning of the monsoon, but trials were carried out at Hyderabad by sowing in October or November as a winter crop. The duration of the crop, especially of the *medium* and *late* cultivars, was much reduced. In 1975*76, October-sown pigeonpeas gave yields comparable to those of the normal season but much lower yields were produced by planting in November 1975. *Medium* and *late* cultivars significantly outyielded early ones. Optimum plant populations for winter crops were 3*5 times higher than are normally used in the monsoon. Pigeonpeas at relatively high population densities could have considerable potential as a winter crop in peninsular India.

The number and percentage of nodes bearing two pods in 'double-podded' cultivars of chickpeas growth in northern India (at Hissar) and peninsular India (at Hyderabad) were compared. At Hissar 11% of the pod-bearing nodes were double-podded; at Hyderabad 28% were double-podded on early-sown and 49% on late-sown plants. In all cases the number of double-podded nodes per plant was similar, but different numbers of single- podded nodes per plant were formed, depending on the length of the growing season. At Hyderabad the percentage of double-podded nodes was not significantly affected by population-density nor by shading the plants throughout the reproductive phase. Partial defoliation of the plants reduced the percentage of double-podded nodes, as did the removal of all flowers from the plants for the first two to four weeks of the reproductive phase. The conversion of 'double-podded' plants to 'single-podded' plants by cutting off one of the flowers at every double-flowered node had no effect on yield at a location in the Himalayas where the double-podded character was poorly expressed, but at Hyderabad the yield of the 'single-podded' plants was significantly reduced compared with the 'double-podded' controls. The results indicate that the double-podded character can confer an advantage in yield of about 6 to 11% under conditions in which the character is well-expressed.

The symptoms of the pigeonpea wilt (causal fungus: Pusarium udum) generally appear during the reproductive phase, particularly while pod-filling is taking place (Mundkur, 1935).

In an off-season crop planted in December 1974 we observed that while there was a high incidence of wilt during the pod-filling phase of untreated plants, almost all the plants where pod development had been prevented by the removal of flowers remained healthy.

Conversely, we found that the incidence of the disease increased when the plants were defoliated during the reproductive phase. In an experiment carried out on medium- duration cultivars grown during the normal season (planted in June 1975) leaves were removed at the time flowering began, and subsequent defoliations were made as new leaves were produced. Different degrees of defoliation were employed: 33% (one leaf out of three removed), 50% (alternate leaves removed), 67% (two leaves out of three removed), 75% (three leaves out of four) and 100% (all leaves removed). We found that, in general, the incidence of the wilt increased with the severity of defoliation.

A second experiment was carried out on medium-duration plants (56 lines in the breeders' plots) which had been ratooned at the time of the harvest of the first flush of pods. These plants regenerated new branches and entered into a second reproductive phase, during which (on March 1 1976) one row of plants of each line was completely defoliated and another row was left as a control. Two months later the plants were scored for wilt. Of the controls, 16 out of 380 plants (4%) had wilted whereas 174 out of 360 defoliated plants (48%) had wilted.

Defoliation of plants in the ICRISAT patholigists' wilt-sick plot has also been found to lead to an increase in the incidence of the wilt disease.

In this review, I discuss the possibility that dying cells produce much of the auxin in vascular plants. The natural auxin, indole-3-acetic acid (IAA), is derived from tryptophan by a two-step pathway via indole pyruvic acid. The first enzymes in the pathway, tryptophan aminotransferases, have a low affinity for tryptophan and break it down only when tryptophan levels rise far above normal intracellular concentrations. Such increases occur when tryptophan is released from proteins by hydrolytic enzymes as cells autolyse and die. Many sites of auxin production are in and around dying cells: in differentiating tracheary elements; in root cap cells; in nutritive tissues that break down in developing flowers and seeds; in senescent leaves; and in wounds. Living cells also produce auxin, such as those transformed genetically by the crown gall pathogen. IAA may first have served as an exogenous indicator of the presence of nutrient-rich decomposing organic matter, stimulating the production of rhizoids in bryophytes. As cell death was internalized in bryophytes and in vascular plants, IAA may have taken on a new role as an endogenous hormone.

1 Although much is known about the effects of plant hormones and their role in the control of growth and differentiation, little is known about the way in which hormone production is itself controlled or about the cellular sites of hormone synthesis. The literature on hormone production is discussed in this review in an attempt to shed some light on these problems.

2 The natural auxin of plants, indol-3yl-acetic acid (IAA) is produced by a wide variety of living organisms. In animals, fungi and bacteria it is formed as a minor by-product of tryptophan degradation. The pathways of its production involve either the transamination or the decarboxylation of tryptophan. The transaminase route is the more important.

3 In higher plants auxin is also produced as a minor breakdown product of tryptophan, largely via transamination. In some species decarboxylation may occur but is of minor important. Tryptophan can also be degraded by spontaneous reaction with oxidation products of certain phenols.

4 The unspecific nature of the enzymes involved in IAA production and the probable importance of spontaneous, non-enzymic reactions in the degradation of tryptophan make it unlikely that auxin production from tryptophan can be regulated with any precision at the enzymic level. The limiting factor fro auxin production is the availability of tryptophan, which in most cells is present in insufficient quantities for its degradation to occur to a significant extent. Tryptophan levels are, however, considerably elevated in cells in which net protein breakdown is taking place as a result of autolysis.

5 An indole compound, glucobrassicin, occurs in Brassica and a number of other genera. It breaks down readily to form a variety of products including indole acetonitrile, which can give rise to IAA. There is, however, no evidence to indicate that glucobrassicin is a precursor to auxin in vivo.

6 Conjugates of IAA, e.g. IAA-aspartic acid and IAA-glucose, are formed when IAA is supplied in unphysiologically high amounts to plant tissues. These and other IAA conjugates occur naturally in developing seeds and fruits. There is no persuasive evidence for the natural occurrence of IAA-protein complexes.

7 Tissues autolysing during prolonged extraction with ether produce IAA from tryptophan released by proteolysis. IAA is produced in considerable quantities by autolysing tissues in vitro.

8 During the senescence of leaves proteolysis results in elevated levels of tryptophan. Large amounts of auxin are produced by senescent leaves.

9 Coleoptile tips have a vicarious auxin economy related to IAA from the seed. These move acropetally in the xylem and accumulate at the coleoptile tip. The production of auxin in coleoptile tips involves the hydrolysis of IAA esters and the conversion of labile, as yet unidentified compounds, to IAA. There is no evidence for the de novo synthesis of IAA in coleoptiles.

10 Practically all the other sites of auxin production are sites of both meristematic activity and cell death. The production of auxin in developing anthers and fertilized ovaries takes place in the regressing nutritive tissues (tapetum, nucellus, endosperm) as the cells break down. In shoot tips, developing leaves, secondarily thickening stems, roots and developing fruits auxin is produced as a consequence of vascular differentiation; the differentiation of xylem cells and most fibres involves a complete autolysis of the cell contents; the differentiation of sieve tubes involves a partial autolysis. There is no evidence that meristematic cells produce auxin.

11 The lysis ad digestion of cells infected with fungi and bacteria results in elevated tryptophan levels and the production of auxin. Viral infections reduce the levels of tryptophan and are associated with reduced levels of auxin.

12 Crown-gall tissues produce auxin. It is suggested that the crown-gall disease may involve at any given time the death of a minority of the cells which produce auxin and other hormones as they autolyse; the other cells grow and divide in response to the hormones.

13 Auxin is produced in soils, particularly those rich in decaying organic matter, by micro-organisms. This environmental auxin may be important for the growth of roots.

14 There is no convincing evidence that auxin is a hormone in non-vascular plants. The induction of rhizoids in liverworts by low concentrations of auxin can be explained as a response to environmental auxin.

15 Abscisic acid is synthesized from mevalonic acid in living cells. It is possible that under certain circumstances, abscisic acid or closely related compounds are formed by the oxidation of carotenoids.

16 The sites of gibberellin production are sites of cell death. It is possible that precursors of gibberellins, such as kaurene, are oxidized to gibberellins when cells die.

17 Cytokinins are present in transfer-RNA (tRNA) of animals, fungi, bacteria and higher plants. They are probably formed in plants by the hydrolysis of tRNA in autolysing cells. There is evidence that they are also formed in living cells in root tips.

18 Ethylene is produced in senescent, dying or damaged cells by the breakdown of methionine.

19 It was shown many years ago that wounded and damaged cells produced substances which stimulate cell division. It now seems likely that the production of wound hormones and the normal production of hormones as a consequence of cell death are two aspects of the same phenomenon. Wounded cells can produce auxin, gibberellins, cytokinins and ethylene.

20 The control of hormone production in living cells is a biochemical problem which remains unsolved. The control of production of hormones formed as a consequence of cell death depends on the control of cell death itself. Cell death is controlled by hormones which are themselves produced as a consequence of cell death.

21 In spite of the fact that dying cells are present in all vascular plants, in all wounded and infected tissues, in certain differentiating tissues in animals, in cancerous tumours and in developing animal embryos, the biochemistry of cell death is a subject which has been almost completely ignored. Dying cells are an important source of hormones in plants; some of the many substances released by dying cells may also be of physiological significance in animals.

A re-examination of the evidence for auxin production by coleoptile tips reveals that it is not conclusive and that several important problems remain unresolved. The possibility that auxin and auxin precursors move acropetally in the xylem was tested by analysing guttation fluid from intact coleoptiles, decapitated coleoptiles and primary leaves of Avena sativa. In all cases two zones of auxin activity were detected on chromatograms of the acidic ether-soluble fraction, one of which corresponded to the Rf of indol-3-yl acetic acid (IAA). Similar auxin activity was found in guttation fluid from seedlings of Zea mays, Triticum aestivum and Hordeum vulgare. Evidence that guttation fluid also contains alkali-labile auxin complexes was obtained. Experiments on the movement of dyes and radioactive IAA introduced into the xylem of transpiring or guttating coleoptiles showed that these substances accumulate at the tip of the coleoptile, or at the apical region of decapitated coleoptiles. The hypothesis that IAA and 'inactive' auxins move acropetally in the xylem from the seed to the coleoptile tip where they accumulate and where the 'inactive auxins' can be converted to IAA is shown to be consistent with the classical work on coleoptiles; it can also explain the autonomous curvature of coleoptiles and the influence of the roots on the auxin contect of coleoptile tips. An analogous accumulation of auxin probably occurs at the tips of primary leaves. The anomalous auxin economy of coleoptile tips is discussed.

Cambium and differentiating xylem and phloem tissues from the trunks of trees of Acer pseudoplatanus L., Fraxinus excelsior L., and Populus tremula L. were extracted with ether and tested for auxin, which was found on chromatograms of the acidic fraction at an Rf corresponding to that of indol-3yl-acetic acid in five solvent systems. In addition, small amounts of auxin with a higher Rf in ammoniacal isopropanol were found in phloem samples. The amounts of auxin were greatest in xylem samples, less in the cambium, and least in phloem. The differences, which cannot be explained in terms of differential losses during extraction and purification, suggest that auxin is actually formed in differentiating xylem tissue. The significance of these results is discussed.

Auxin was detected in samples of substrata supporting bryophytes in a variety of locations in both Britain and Malaya. Activity occurred on chromatograms at zones corresponding to the Rf of indole acetic acid. The range of concentrations found, 0.4-10.4ug/1, probably represents a two-to five-fold underestimate due to losses during extraction and purification. The amounts of auxin in samples of soil on which bryophytes were not growing were within the same range. The importance of this environmental auxin for the induction of rhizoids in liverworts and for roots of higher plants is discussed.

Autolysing plant tissues are known to produce auxin when extracted with ether. It has been shown that autolysing plant, yeast and rat liver tissues produce auxin in vitro; this suggests that relatively unspecific mechanisms are involved. Furthermore, sterile plant and animal tissues which have been killed by freezing and thawing induce nodules of differentiated cells in a previously undifferentiated callus of Phaseolus vulgaris. The callus tissue is known to differentiate in response to applied gradients of auxin. Plant and animal tissues killed by boiling were considerably less effective in inducing differentiation in the tissue. The evidence indicates that auxin is a normal product of autolysing cells. It is suggested that dying cells are an important source of auxin in the plant.

In senescent leaves proteins are hydrolysed to amino-acids and peptides, which might be expected to release protein-bound auxin and also to provide considerable amounts of trypotophan which can be converted by many plant tissues to the auxin indolyl-3-acetic acid (IAA). We have therefore investigated the concentrations of auxin in senescent leaves.

Mature trifoliate leaves from plant of Phaseolus vulgaris and leaves from young plants (2-3 weeks old) of Avena sativa were detached and placed with their petioles or bases in distilled water in the dark at 25° C. In these conditions, the leaves become senescent and turn yellow. Samples were taken at various times (at intervals of 1 or 2 days), weighed and stored in the deep freeze until they were extracted with peroxide-free ether for 3 h at 0° C. The ether extract was partitioned and the acidic fraction was run on paper chromatograms with isopropanol : ammonia : water (8:2:1 v/v). The zone corresponding to IAA was eluted and the auxin was estimated using an Avena coleoptile straight growth bioassay. The amounts of auxin extracted from the leaves at various times are shown in Figs. 1 and 2.

It can be seen that in both cases there is a large increase in the amount of auxin present over a period of 6 days. The amounts measured represent the resultant of auxin production and auxin destruction: in the case of Avena, after about the fourth day the rate of destruction exceeds the rate of production. The fall in total auxin was observed in each of six experiments.

The level of auxin in leaves and petioles is involved in the control of abscission so the production of auxin by senescent leaves, if it is a general phenomenon, may be an important factor which so far has been overlooked.

The formation of callus at the basal end of tobacco internode tissues cultured on a basic medium has been used as an indication of the presence of auxin within the tissues. It has been shown in this way that sections of internode are capable of producing auxin. This production of auxin is related to the continued activity of the vascular cambium. If cambial activity and vascular differentiation are eliminated, auxin is no longer produced. When tissues in which cambial activity and vascular differentiation are taking place are cultured on a medium containing an inhibitor of polar auxin transport, tri-iodo benzoic acid, serried ranks of xylem tracheids are formed. It is suggested that auxin is produced as a consequence of xylem differentiation and the observations reported in this paper are interpreted in the light of this hypothesis. It is also suggested that kinins may be produced as a result of xylem and phloem differentiation, and the possibility that autolysing cells are a major source of both auxins and kinins in the plant is discussed.

Segments of mesocotyls of Avena sativa L. transported (1-14C) indol-3yl-acetic acid (IAA)with strictly basipetal polarity. Treatment of the segments with solutions of sorbitol caused a striking increase in basipetal auxin transport, which was greatest at concentrations around 0.5M. Similar effects were observed with mannitol or quebrachitol as osmotica, but with glucose or sucrose the increases were smaller. Polar transport was still detectable in segments treated with 1.2M sorbitol. The effects of osmotic stress on the polar transport of auxin were reversible, but treatment with sorbital solutions more concentrated than 0.5M reduced the subsequent ability of mesocotyl segments to grow in response to IAA. The increased transport of auxin in the osmotically stressed segments could not be explained in terms of an increased uptake from donor blocks. The velocity of transport declined with higher concentrations of osmoticum. The reasons for the enhancement of auxin transport by osmotic stress are not known.

Auxin (IAA) transport was investigated using crown gall suspension tissue culture cells. We have shown that auxin can cross the plasmalemma both by transport of IAA anions on a saturable carrier and by passive (not carrier-mediated) diffusion of the lipid-soluble undissociated IAA molecules (pK=4.7). The pH optimum of the carrier for auxin influx is about pH6 and it is half-saturated by auxin concentrations in the region of a 1-5u-M. We found that the synthetic auxin, 2,4D specifically inhibited carrier-mediated IAA anion influx, and possibly also efflux. Other lipid-soluble weak acids which are not auxins, such as 3,4-dichlorobenzoic acid, had no effect on auxin transport. By contrast, we found that TIBA, an inhibitor of polar auxin transport in intact tissue inhibited only the carrier-mediated efflux of IAA.

When the pH outside the cells is maintained below that of the cytoplasm (pH7), auxin can be accumulated by the cells: In the initial phase of uptake, the direction of the auxin concentration gradient allows both passive carrier-mediated anion influx (inhibited by 2,4D) and a passive diffusion of undissociated acid molecules into the cells. Once inside the cytoplasm, the undissociated molecules ionise, producing IAA anions, to a greater extent than in the more acidic extra-cellular environment. Uptake by passive diffusion continues as long as the extra-cellular concentration of undissociated acid remains higher than its intra-cellular concentration. Thus, the direction of the auxin anion concentration gradient is reversed after a short period of uptake and auxin accumulates within the cells. The carrier is now able to mediate passive IAA anion efflux (inhibited by TIBA) down this concentration gradient even though net uptake still proceeds because the carrier is saturable whereas passive diffusion is not.

Auxin 'secretion' from cells is regarded as a critical step in polar auxin transport. The evidence which we present is consistent with the view that auxin 'secretion' depends on a passive carrier-mediated efflux of auxin anions which accumulate within the cells when the extra-cellular pH is below that of the cytoplasm. The implications of this view for theories of polar auxin transport are discussed.

The original, basipetal polarity of auxin transport persisted in the stems of inverted cuttings of Tagetes, tomato and tobacco in spite of the reversal of the relative positions of the roots and shoots. No significant acropetal auxin transport could be detected even after four months growth. These results indicate that the polarity of newly formed cells in secondarily thickening internodes is determined by the existing polarity of auxin transport within the tissues.

Auxin transport was investigated in excised stem segments of Nicotiana tabacum L. by the agar block technique using (I-14C) indol-3yl-acetic acid (IAA). The ability of the stems to transport auxin basipetally increased as secondary development proceeded; by contrast the ability of the pith to transport auxin declined with age. By separation of the stem tissues it was shown that the great majority of auxin transport took place in cells associated with the internal phloem and in cells close to the cambium; in both cases similar velocities of transport were found (c 5.0 mm h-1 at 22°C). The effects of osmotic gradients on auxin transport through the internal phloem were investigated. IAA was found by chromatography to account for practically all the radioactivity in receiver blocks and ether extracts of stem segments. The significance of these results is discussed.

The uptake of the auxin indol-3-yl acetic acid (IAA) into plant cells is of interest not only because this compound is a hormone, but also because its movement across the plasma membrane is probably involved in the polar transport of auxin. The plasma membrane contains auxin binding sites and may be a primary site of hormone action.

IAA partitions into non-polar solvents from acidified aqueous solutions because the undissociated acid is more soluble in such lipid solvents than in water. There is known to be a passive, non-metabolic component of the uptake of IAA and of the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) into plant tissue which has been ascribed to the diffusion of the undissociated acid across the plama membrane. A carrier-mediated mechanism for auxin anion uptake is also possible but has not been conclusively demonstrated.

Uptake by the diffusion mechanism is linearly related to the concentration of the undissociated acid which is a function of the acid's pK and the pH of the incubation medium. If the pH of the medium is lower than that of the cells, the cells accumulate weak acid; the equation requires that the concentration of undissociated acid should be the same in each compartment. Thus the relation between the initial rate of uptake and pH should resemble a dissociation curve with a midpoint at the pK of the weak acid. This prediction is realized for the uptake of benzoic acid (pK=4.2) by yeast but not by the bacterium Proteus vularis, when, although the curve is still that of a dissociation, its midpoint is displaced by 1 pH unit above the pK of benzoic acid. Such displacement seems fairly widespread. By collating data from ninety experiments on pH dependence of biological effects of weak acids, a composite curve is obtained relating pH to log concentration of acid required to give a standard response; the midpoint of the curve is at a higher pH than the pK. Data on IAA and 2,4-D uptake reveal a similar effect. Here we suggest an explanation of this displacement which may be of general biological significance.

Almost nothing is known about the establishment of cellular polarity underlying the polar auxin transport system of higher plants. Osborne has suggested that the apical ends of cells derived from an apical meristem by sequential divisions are younger than the basal ends: their polarity and the basipetal transport of auxin are due to this age difference. Sachs in his work on regenerating vascular strands has found that gradients of auxin may be responsible for establishing the cellular polarity and the subsequent transport of auxin in the direction of the initial gradient. Shoot tips and expanding dicot leaves contain relatively high levels of auxin. The basipetal polarity of auxin transport in petioles and stems is therefore associated with basipetal auxin gradients. In grass coleoptiles the greatest amounts of auxin are found at the tip, where basipetal auxin transport is also associated with basipetal auxin gradients."

In monocot leaves which grow by a basal intercalary meristem, the pattern of cell division and of auxin distribution is more or less the reverse of that found in shoot tips. Sequential divisions of the basal meristem presumably make younger the basal ends of cells; and in growing monocot leaves the greatest amounts of auxin are found at the base. The polarity of auxin transport in monocot leaves is therefore of considerable interest.

Hertel and Leopold reported that in the primary leaf of Zea mais, auxin transport was basipetal. No other references to auxin transport in monocot leaves are available and I therefore tested the leaves of a number of species. In every case auxin transport was basipetal.

In leaves of young plants of Avena sativa, basipetal auxin transport took place across the meristematic region at the base of the leaf and also in the leaf sheath, which grows by a basal meristem. Plants germinated and grown in darkness yielded similar results. Less auxin transport was found near the leaf tip than in the younger, more basal parts of the leaf and younger leaves had a greater ability to transport auxin than older leaves. A decline in the ability of cells to transport auxin as they grow older has been observed in a number of other species and tissues.

Homogenates of differentiating xylem and phloem tissue have higher cellulase activities than cambial samples; the highest activity is always found in phloem. Callus tissue, in which no vascular differentiation occurs, contains only low cellulase activity. The results suggest that cellulase is involved in vascular differentiation.

Different pH optima of cellulase activity were found: in cambium, xylem and phloem tissue, cellulase activity with an optimum at about pH 5.9 is predominantly membrane-bound; it is sedimentable at 100,000 g and releasable by Triton X-100. The same may be true of activity with an optimum at pH 5.3. Phloem tissue also contains a soluble, cytoplasmic cellulase of high activity at pH 7.1 and xylem tissue contains cytoplasmic cellulase with an optimum at pH 6.5. Low cellulase activity with a pH optimum similar to that of xylem homogenates was found in xylem sap. Cellulase activity in abscission zones increases greatly just before leaf abscission. Abscission zone cellulase has two pH optima, et 5.3 and 5.9; both activities are increased by Triton treatment of homogenates. The possible existence of several different cellulases forming part of a cellulase complex, and the role of the enzymes in hydrolysing wall material during cell differentiation are discussed.

Using a viscometric method of the latex of Hevea brasiliensis was found to contain a highly active cellulase capable of hydrolysing carboxymethyl cellulose. The enzyme has a pH optimum of around 6.3. It is present in the serum of the latex and is not membrane-bound to any significant extent. Similar cellulase activities were detected in latex from old and new latex vessel rings and also in latex from regularly tapped vessels and newly tapped vessels. The possible role of the enzyme in the removal of cell wall material during the differentiation of latex vessels is discussed.

Cellulase was found to be present in the latex of species with articulated laticifers but it could not be detected in the latex of species with non-articulated laticifers. It is suggested that cellulase is involved in the removal of end walls during the differentiation of articulated laticifers.

Bleeding sap of Actinidia chinensis and Betula populifolia and guttation fluid of Avena sativa were analysed for sugars, amino-acids, auxin, and certain enzymes. A wide range of amino-acids was found in all three. Auxin was not detected in the bleeding sap, but was present in Avena guttation fluid (5.1 ug IAA equivalent/1). 'IAA oxidase', acid phosphatase, ribonuclease, deoxyribonuclease, and protease were detected in the bleeding sap and guttation fluid. The possibility that some of the substances found in sap and guttation fluid are products of autolysing, differentiating xylem cells in the roots is discussed.

Ageing, death, and potential immortality lie at the heart of biology, but two seemingly incompatible paradigms coexist in different research communities and have done since the nineteenth century. The universal senescence paradigm sees senescence as inevitable in all cells. Damage accumulates. The potential immortality paradigm sees some cells as potentially immortal, especially unicellular organisms, germ cells and cancerous cells. Recent research with animal cells, yeasts and bacteria show that damaged cell constituents do in fact build up, but can be diluted by growth and cell division, especially by asymmetric cell division. By contrast, mammalian embryonic stem cells and many cancerous and ‘immortalized’ cell lines divide symmetrically, and yet replicate indefinitely. How do they acquire their potential immortality? I suggest they are rejuvenated by excreting damaged cell constituents in extracellular vesicles. If so, our understanding of cellular senescence, rejuvenation and potential immortality could be brought together in a new synthesis, which I call the cellular rejuvenation hypothesis: damaged cell constituents build up in all cells, but cells can be rejuvenated either by growth and cell division or, in ‘immortal’ cell lines, by excreting damaged cell constituents. In electronic supplementary material, appendix, I outline nine ways in which this hypothesis could be tested.

The ageing and death of cells in higher plants and higher animals are discussed in relation to cellular rejuvenation by growth and division. The full text article is available for download in the the following formats.

Death is out of fashion, rarely discussed forgotten as much as it can be. It is too close to us all. But however much or little we may choose to think about our own inevitable mortality, death is a fact of life which must be considered by any science of life. But even within biology death has been more or less ignored. I think that this has imposed a great limitation on our understanding of life itself.

There has recently been an increased interest in end-of-life experiences (ELEs) in humans, but ELEs in non-human animals have not yet been assessed. In this paper, we present findings from a study we performed to collect and analyze reports about remarkable behavioral aspects of animals during their last phase of life. After public appeals in which we asked for reports about ELEs in animals, we received numerous responses from pet owners. We were able to group these experiences into specific categories, which we termed the last goodbyes, last visits, last rally, retreating into solitude, unusual premonitions of death, somatic surprises, terminal lucidity in animals, and potential near-death visions in animals. We present 43 case reports pertaining to these different categories. Many of them show striking similarities to remarkable behavior reported by dying people. This similarity between animal and human ELEs might be a sign of a common physiology underpinning such experiences and could also increase the recognition that animals share an inner life similar to that of humans during all phases of life. This could lead to a more respectful treatment of pets, as well as of animals in farms, zoos, and in the wild. However, as our study was of a preliminary character and only the first of its kind, we encourage further systematic research in this field. In the Supplementary Material, we publish 71 additional cases for those who would like to study more examples.