Rivista di Biologia - Biology Forum 85 (3/4), 1992, 455-460
by Rupert Sheldrake
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 differencies 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 for-
mative 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. This is the background to my present
paper Formative Causation and Rose's response to it.
Before discussing our interpretations, I briefly review what we have in
common. A large decline in latency with both test and control stimuli
occurred in the first week: in other words the chicks pecked at the
stimuli much sooner. Rose and I agree that this effect was largely, if not
entirely, a result of Ms Harrison learning how to test the chicks. This
was the largest single effect in the whole experiment, and inevitably
dominates the statistics in any overall analysis. We agreed to analyse
separately the results from the second week onwards to see more clearly
what happened in the rest of the experiment. We agree that the continued decline in latency in the control chicks (not predicted by either of
us) is best explained as a result of Ms Harrison's increasing familiarity
with the chicks and the test procedures. Both of us failed to forsee these
obvious experimenter effects, and therefore we were both equally wrong
in our prediction that latencies in the control group would show no secular trend over the course of the experiment.
Our essential disagreement concerns the trend in the differences between the latencies with yellow light (test) and chrome bead (control).
Rose wrongly predicted that there would be no trend in these differences. There was in fact a trend (my Figs 4 and 6), consistent with a
morphic resonance effect. As the experiment progressed, there was a
cumulative increase in the number of previous chicks that had developed an aversion to pecking the yellow light because they had been made sick, and hence by morphic resonance subsequent chicks showed an increasing tendency to avoid it, even though they themselves had not
been made sick. This increasing aversion to pecking the yellow light
countervailed the tendency to peck sooner as a result of the experimenter's practice.
Both Rose and Bateson offer an alternative explanation of this same
trend in terms of "floors" and "ceilings". If their arguments are confusing
to the reader, this is not surprising-, Rose and Bateson each use the
words "floor" and "ceiling" in the opposite sense. They claim that soon
after the experiment began, the latency scores for the yellow light
reached a minimum, which Rose calls a "floor" and Bateson calls "an
obvious ceiling effect", and then stayed at this limit, unable to fall lower
in spite of the experimenter's continued improvement. Meanwhile the
latency scores for the chrome bead, which started off higher, continued
to decline as a result of the experimenter's practice. This, they claim,
explains the difference over time between the latencies for the test and
I acknowledge that "floor" and "ceiling" effects could arise in experiments of this type, and preclude the drawing of strong conclusions. In
future research it will be important to use a design that can rule out
this objection conclusively, for example by repeating the present experiment using control and test stimuli with similar mean latencies, starting off neither too high nor too low. (The preliminary research for such an experiment, comparing the latencies with different stimuli, would
also enable the experimenter to get used to testing the chicks, and hence
reduce the experimenter practice effect within the main experiment).
But can "floor" effects in fact explain the data in the present experiment? An inspection of the actual data (my Fig. 3; cf Rose's Fig. 2a shows that with the yellow light the supposed minimum latency was reached after the first 6-9 days; but far from remaining at this "t\oor"
the latencies thereafter increased up to around the 30th day.
The "floor" explanation is even less convincing when considering the
other relevant set of data, that obtained by testing control chicks after
they had received an injection of saline solution. Here there was a clear
tendency for latencies with the yellow light to increase while those for
the chrome bead declined (my Fig. 5), with no sign of "floor" or "ceiling
effects. Rose and Bateson simply ignore these results.
I should also point out that there is a serious systematic error in the
data used by Rose, as shown in his Fig. 2a and 2b. These data exclude
all the chicks that failed to peck the stimulus during the 30s training
period (recorded as having the maximum latency of 30s). The data on
these maximum-latency chicks had been recorded separately, and were
mistakenly omitted from the data-file entered into the computer.
brought this mistake to Rose's attention at an early stage in our discussions, and supplied him with the corrected data. But he is still using the erroneous data-file. Hence his statistical analysis is wrong, and so is his conclusion: "There are thus no significant differences between the secular trends in either yellow or chrome beads, even with the 'correction' of
omitting the first days of the experiment. Thus the crucial prediction
made by the hypothesis, which Sheldrake agreed before the experiment
began, is also disconfirmed". Repeating Rose's analysis with the right
data shows that the secular trends are in fact significantly different at
the p=0.01 level (using the Williams test, as described by HOWELL (1987). The crucial prediction was confirmed, not disconfirmed.
I now turn to other points raised by Rose in his response:
1 Rose shows in his Fig. la and lb data for the behaviour of chicks that
have been made averse to the yellow light by an injection of lithium
chloride. There is no problem here. We agree that a strong aversion was
in fact established.
Rose and I agreed from the outset that the crucial measurements
were of latencies to peck, rather than the number of pecks the chicks
made after they first pecked and before the end of the 30s test period.
Once the chicks have overcome any initial aversion to pecking the
stimulus, the subsequent number of pecks depends on several factors,
including the remaining time available in the test period (chicks that
first peck at 29s obviously have less scope for further pecks than those
that peck at Is) as well as the general level of activity of the chicks,
which is influenced by the weather during incubation, in particular the
atmospheric pressure, as BATESON (1974) has shown. (Variations in
general activity probably also affect the latency, but may well affect peck
nember to a greater extent). Rose introduced peck numbers in his Fig.
lb and 2b but failed to point out how unreliable they may be as an
index of aversion. In any case, the data in his Fig. 2b and the statistical
analysis based upon them are erroneous for the reasons given above.
Rose quoted Bateson's remarks to add authority to his own position.
But Rose and Bateson differ considerably in their approach. Bateson
employed a method of statistical analysis involving the median latencies
in 7-day blocks. Bafore we received Bateson's comments, Rose and I
agreed that in analysing this experiment, means were in general more
informative than medians. We also agreed that the linear regressions
provided a simple and appropriate way of analysing secular trends.
Bateson's method is much blunter. Instead of looking for overall trends,
it involves the comparison of median latencies for the control and test
stimuli in each separate 7-day block.
Despite quoting Bateson's remarks approvingly. Rose still uses means
(albeit incorrect ones) in his analysis of the data (his Figs 2a and 2b)
and analyses the trends by means of regressions. Thus in terms of statistical methodology, Rose and I are in closer agreement with each other
than we are with Bateson. Indeed, I think one of the best ways of ana-
lysing the data is to use Rose's own method, routinely followed in his
own laboratory, namely to use as a measure of aversion the proportion
of the chicks in any given sample that do not peck at the stimulus with-
in the first 10s. This is the method I used in the analysis of data shown
in my Figs 2, 3 and 4.
If morphic resonance takes place, then the response of chicks to
stimuli routinely used in similar experiments, such as chrome beads and
coloured LEDs, should be influenced by what happened in previous ex-
periments. Such stimuli would not be tabulae rasae. In order to mi-
nimize background morphic resonance, and also to reduce any possible
interference from concurrent aversion experiments with chicks, Rose
and I agreed to use a yellow LED, a stimulus which has not, so far as
we know, been used in previous research with chicks. Red and green
LEDs are commonly employed. The chromium-plated bead used as the
control stimulus has been used in previous aversion experiments, sometimes as a test stimulus and sometimes as a control.
In general, as Bateson points out, the chicks pecked sooner at the yellow
than at the chrome bead. He suggests that this was because "the yellow
light caught the attention of the chicks to a greater extent than the
chrome bead". He does not explain why this should be so. Is the yellow
light more attractive because it is a light, yellow, or both? The first of
these possibilities can be ruled out, because LEDs in other colours are
relatively unattractive. In a subsidiary experiment designed by Rose and
myself and carried out by Ms Harrison, we compared the mean latencies
to peck at the chrome bead, the yellow LED, and a green LED of the
type regularly used by Rose's group in aversion experiments (e.g. BARBER et al., 1989). The mean latencies were 4.1 (n=27) for the yellow LED, 8.9s (n=56) for the chrome bead and 18.0s (n=29) for the green LED. Maybe the chicks' strong aversion to pecking the green LED was,
at least in part, a result of morphic resonance from chicks exposed to
green LEDs in previous aversion experiments.
In this context, Bateson's final remark does not make much sense to me:
"the evidence that, overall, the chicks pecked more quickly at the yellow
bead than at the chrome bead runs counter to the prediction from the
morphic resonance hypothesis, and [Sheldrake's] analysis obscures this
fact". The yellow light was chosen because it was a fresh stimulus, not
associated with a background morphic resonance from averse chicks in
previous experiments, unlike the chrome bead. The fact that the yellow
light was more attractive from the outset does not run counter to any
prediction from the morphic resonance hypothesis; if anything, it tends
to support it. But perhaps Bateson means that the yellow bead, in spite
of being more attractive to start with, should by morphic resonance have
rapidly become less attractive than the chrome bead; if so, he is ignoring
the background morphic resonance from previous chicks averse to the
chrome bead. Or perhaps Bateson means something else. Who is being
On the basis of confused reasoning, erroneous data and selective use of
evidence, Rose announces that the hypothesis of formative causation is
"disconfirmed". This categorical statement is a good example of his polemical style, familiar to me from our debate over the nature of memory in The Guardian, in the course of which he seriously misrepresented the experimental evidence. Rose has had many years of experience in the realm of political controversy. His technique is to try and endow his own
belief with a tone of objective authority. At the same time he tries to discredit opposing opinions by playing on prejudices. In the present case, he gratuitously attempts to associate the hypothesis of formative causation with creationism, pseudoscience, parapsychology, crop circles,
deep ecology, homeopathy, anti-rationalism and whatever else seems
likely to arouse negative responses in readers who share his general
beliefs. I imagine Rose would disapprove of such tactics on moral
grounds if they were used by his political opponents. The results of this experiment do not disconfirm the hypothesis of formative causation, as Rose claims. They are consistent with it.
London, September 1992
For References and Figures, see Sheldrake's first article An Experimental Test of the Hypothesis of Formative Causation
Top of Page