About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Tuesday, January 31, 2012

Rationally Speaking podcast: Parapsychology

In this episode, Massimo and Julia take on parapsychology, the study of phenomena such as extrasensory perception, precognition, and remote viewing.

Its practitioners claim that there is more evidence for it than there is for other areas of scientific inquiry, such as string theory for which there is no empirical data at all. Yet string theory is taken seriously as a science whereas parapsychology is not.

So, what is the scientific status of parapsychology? What does the best academic literature on the subject tell us? Finally, what can we learn from parapsychology about the practice of science in general?


  1. Massimo,

    Of course there is more evidence for paraphenomena than for most other areas of inquiry. In fact, there is so much evidence the majority of the relevant scientific community actually does not *really* reject paraphenomena -- per highly unscientific anonymous surveys most secretly accept the evidence as confirmatory, and those who ostensibly do not accept the evidence simply are biased or wilfully ignorant. In addition, if you are wondering why parapsychology does not enter into mainstream research programmes if most researchers accept paraphenomena as real effects, it is because there is a conspiracy at play.

  2. ... and why is the conspiracy not discovered? Because there is a conspiracy against the conspiracy. It's turtles all the way down.

  3. Julia, so good to hear that you thought you were a psychic when quite young. Me, I had dreams where I could fly. They stopped when I was about 10, but I am awake now and still remember and feel what it was like running down a hall, putting out my arms like Superman and just falling down a bunch of times, but after 4 or 5 tries, I would be gently lifted into the air, feeling it most in my abdomen, and learning to control left and right turns with arm movements. Some nights were so good it was simple, other nights I could not fly at all. The only recurring 'psychic' dream I have (every couple of years) is seeing and feeling myself 'out in space' looking at a very small blue Earth, then immediately be whisked further away. All that I can say for sure is that the Earth is no longer visible, but the feeling of being transported elsewhere is palpable.

    You say you thought you were psychic, I say you experienced stuff that cannot be explained by your beliefs.

    Most of this podcast was about the art and implementation of studies, so it did not resonate, and my commute ended when y'all starting talking about parapsychology itself.

    Re the usual dismissal of PSIers invoking QM, well its just science. Nobody really understands any science anyway, we just like its predictive powers. Anyway, it seems that there are no arguments from the past century based on relativity and QM that couldn't be made hundreds of years ago about how the 'spooky' and 'spiritual' are as real as the nose on your face. Its just easier these days to make the reverse argument, that in no way is the nose real - by any stretch.

    That's why Massimo, I have to stick with anything that can be imagined is possible. Cause as an entity, the only difference between the thing you imagine and the thing you actually do is the potential interference of other entities. To recall a previous thread from this blog in 2010. that's why your real-world flight from NY to Rome is simply an implementation of any number of flights in your head. Other entities operating in self-interest collaborate/conspire to make it become 'real'. Not saying that other entities cannot also be at work in your imagination.

    This is what it means to be rational. It's about playing well with other entities. It's about social and environmental contracts. But the close-mindedness is really stifling. Much like the current state of politics keeps good people out of the field, the way academia still pretty much closes its doors to things allowed via 20th c. science - this is simply not excusable.

  4. Dear Massimo and Julia,

    I was surprised but pleased to see this podcast. Perhaps not surprisingly, I have some comments about what was discussed:


    (1) You mentioned that some Ganzfeld meta-analyses showed positive and significant effects, and that some did not, and your example of one that did not was the Milton-Wiseman meta-analysis in 1999. However, I felt that that was a bit of a misleading characterization of the situation. As I mentioned in my RS post on parapsychology, there have been 8 independent, published Ganzfeld meta-analyses since 1985. And with the exception of the Milton-Wiseman meta-analysis, all of them have reported statistically significant effects well below the 1% level. Moreover, the Milton-Wiseman meta-analysis was later shown by statistician Jessica Utts to have used a fundamentally flawed statistical estimate of the effect size and significance level of the combined results. Utts showed that if you use a method that weighs each study by trial size (e.g. the exact binomial test), then the overall results are significant at the 4% level. I even wrote to Wiseman to ask for his response to Utts' critique, and he confirmed to me that it was a valid criticism. So when one considers this, it turns out that 8/8 Ganzfeld meta-analyses since 1985 have found results that are statistically significant below the 5% level. Ergo, the results of the meta-analyses have actually been quite reliable.

    (2) Re the Bem-Honorton Ganzfeld meta-analysis in 1994 (which combined the results of 11 experiments from the PRL Ganzfeld lab over a period of 8 years), yes, the putative file-drawer was calculated by Honorton to be 15:1 (which Hyman agreed to). But the more important point is that Bem and Honorton explicitly declared that ALL trials were published, so that there is no file-drawer from the PRL lab.

  5. Massimo:

    (1) Re your comment about the effect size in Ganzfeld experiments being too large, it seems to me that it was based on a misunderstanding of the nature of effect sizes in social science. When parapsychologists say the effect size in Ganzfeld studies is "small", they are simply using the convention of effect size measures that are standardly used in statistics and social science. For example, the standard measure of effect size called Pearson's correlation coefficient, r, defines a "small" effect of r = 1 - 3, which is precisely the range within which the overall effect size from Ganzfeld studies falls. Also, with an effect size in this range, one cannot merely assume that positive results should always be obtained in every study. One has to do a power analysis (which is standard statistical practice for the design of any study), which tells you the probability of achieving a statistically significant result in a predicted direction, for a given effect size. For the 31.5% hit rate found in the latest Ganzfeld meta-analysis, and with a study of trial size N = 40 (which is the mean trial size of Ganzfeld studies in the latest meta-analysis), the statistical power to achieve a significant result at the 5% level is only 26%. And in the latest Ganzfeld meta-analysis, you'll notice that 27/102 (or ~26%) of the studies were independently significant at the 5% level (which is still significantly above what would be expected by chance alone).

    (2) The comment about how a "hit" vs "miss" is defined in the Maimonides studies was incorrect, I'm afraid. The Maimonides studies were designed just like the Ganzfeld studies in that there was 1 randomly chosen target image and a set of decoy images (5 in the case of the Maimonides studies). A "hit" was defined as simply when the blind judge ranked the target image a 1st place match with the dream mentation of the receiver (they used rank-ordered judging). The probability of such a 1st place rank-matching occurring by chance is 1/6. Ergo, there is a 1/6 chance of a "hit", and a 5/6 chance of a "miss". That's standard binomial statistics, and there is no ambiguity in it.

    (3) About the file-drawer, it seems you said that it is more of a problem for parapsychology than for other fields, because we don't know much about the publication trends in parapsychology. But this is actually not true. Consider the following points: (a) The parapsych journals have had a policy since the 1970's of publishing replication attempts with null results; (b) Susan Blackmore directly assessed the number of unpublished Ganzfeld studies in 1980 and found that 7/19 were positive and significant, and thereby ruled out the file-drawer for Ganzfeld research; (c) The fraction of Ganzfeld studies from the PRL lab that produced significant results was comparable to the fraction found by Blackmore; (d) the Ganzfeld procedure requires a special laboratory, Ganzfeld research is a small field in which all the researchers know each other, and there are a limited number of journals in which such results would be published.

    (4) Re your comment about the PEAR lab protocol, and the problem of making perfectly random random number generators, it doesn't seem to take into account that they used a tri-polar protocol (where the intention of the human operator was randomly switched between HI, LO, and BASELINE). The PEAR lab data showed the HI and LO deviations from chance matched the tri-polar protocol exactly as predicted, which would be massively implausible if there were just small random biases on the random number generators. Even the 2 German groups found the exact same data trends, even though the trends never went above statistical significance.

  6. (5) Re your comment about the quality of the parapsych research being as good as the quality of research in mainstream psychology, I mentioned to you the NRC study by Harris and Rosenthal, the comment by Chris French, and the study by Rupert Sheldrake (comparing the rate of use of double-blind protocols in parapsych vs mainstream psych), all of which conclude that the best research in parapsych actually exceeds the quality of research in run of the mill mainstream psych.

    (6) Regarding the "lack of theory" in parapsychology, I gave you a couple references to theories that make empirically testable predictions in my rebuttal to your essay on this topic (e.g. Decision Augmentation Theory and Consciousness Induced Restoration of Time Symmetry). Both of them are also consistent with the laws of physics, as far as I can tell (and remember that I am a theoretical physicist).

    (7) You gave the "more than a century" argument again. But recall that in my rebuttal post, I cited the study by psychologist Sybo Schouten, who found that the total financial and human resources devoted to parapsych since 1880, is equivalent to only 2 months worth of such expenditure in mainstream psychology research in 1985. So, caveat emptor!


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