Feeling the future

[winterkoninkje]

Hat tip to homasse:

Experimental evidence for precognitive ability

The paper, due to appear in the Journal of Personality and Social Psychology before the end of the year, is the culmination of eight years' work by Daryl Bem of Cornell University in Ithaca, New York. "I purposely waited until I thought there was a critical mass that wasn't a statistical fluke," he says.

It describes a series of experiments involving more than 1000 student volunteers. In most of the tests, Bem took well-studied psychological phenomena and simply reversed the sequence, so that the event generally interpreted as the cause happened after the tested behaviour rather than before it.

The alternative interpretation of this work is that the interpretation of previous studies as causation (e.g., typing a random selection of words causes improved recall of those words in a second task) is flawed. Technically all that has been found is that there's a typing-then-remembering correlation (in previous studies) and a remembering-then-typing correlation (in this study). Correlation does not imply causation; so even though the causative story is extremely plausible in the old studies and no non-precognitive causative story seems plausible in the current study, that doesn't necessarily mean that either causative story is correct.

For all the hard scientifical review the preprint is receiving, I'm surprised that this point hasn't been mentioned anywhere. IMO, refuting the standard causative story would be just as fascinating as supporting the precognitive story. It would imply that there are macro-scale quantum effects (e.g., where remembering words from a list and typing random words from that list are coupled), whereas it has long been believed that quantum effects only arise at scales too small to be detected by unaided human perception. If there really are macro-scale quantum effects, it seriously fucks with both physics and philosophy (to say nothing of psychology). Whichever way it turns out, it's still awesome.

Edit (2011.06.29): Here is an excellent examination of a lot of the debate this article caused.

Comments

[lederhosen]

I'm a bit dubious of the stats here:

"I purposely waited until I thought there was a critical mass that wasn't a statistical fluke," he says.

That bit there is a red flag to me. The decision about when to stop an experiment should NOT be based on the significance figures for results to date, otherwise you're at great risk of cherry-picking.

If I run a random number generator and keep rerunning the p-value, I will see that drift all over the place. Every so often, it'll drift into 'significant' territory; as the trial goes on that drift will slow, but wait long enough and you can meet any significance threshold you like.

If you have a few hundred colleagues running similar experiments, all holding off on publishing until they get a strong finding, you can get some *really* impressive-looking results.

[tim]

...which would certainly explain why no one else has been able to reproduce his results.

[lederhosen]

Now I check the link you posted, it covers this and some other cherry-picking issues really well.