ESP and Statistics

There has been lately much talking among the statistical community on the paper about extrasensory perception recently published by the well recognized Journal of Personality and Social Psychology. To tell the truth I did not read the paper, maybe because I think the articles I read about the subject, like this one and this one, tells me all I need to know.

Shortly, the paper claims to have found evidence of extrasensory perception which is to say that what happens in the future can influence things now. The world of causality as we define it today would be completely shaken because we would no longer be able to say that if X causes Y, then X happens before Y. The paper claims to have found significant effects in experiments, like this, from the linked article:

"In another experiment, Dr. Bem had subjects choose which of two curtains on a computer screen hid a photograph; the other curtain hid nothing but a blank screen.

A software program randomly posted a picture behind one curtain or the other — but only after the participant made a choice. Still, the participants beat chance, by 53 percent to 50 percent, at least when the photos being posted were erotic ones. They did not do better than chance on negative or neutral photos."

It is weird to think people will be able to influence the randomly generated image that they will see in the next moment. Well, in fact I found this non sense because random things generated by a computer are not really random, which is to say that there is no way one would have any influence in the random process since the random sequence is already generated to start with. So to me the experiment does not seems good, but I did not read the details of the experiment, so I don't know.

The point I want to make is that this is likely to be another example of bad use of significance testing, and maybe the paper's biggest contribution will be as and example of how not to do things. The answer to whether or not the effects are real will come only with replication, that is, when others do the same experiment and get the same results.

It is also interesting to see that such a polemic paper was published in such a high level journal. I think when things are polemic the journal should ask for more evidence, maybe, and be more careful on judging the paper.

It will be interesting to watch for what will come on this subject...