Renaissance Grrrl

Only recently, thanks to the computer, has it become feasible to solve real, nontrivial problems of reasoning from incomplete information, in which we use probability theory as a form of logic in situations where both intuition and "random variable" probability theory would be helpless. This has brought out the facts in a way that can no longer be obscured by arguments over philosophy. One can always argue with a philosophy; it is not so easy to argue with a computer printout, which says to us: "Independently of all your philosophy, here are the facts about what this method actually gives when applied."

Daaamn. That's some gettin' told right there.

The above quote (emphasis added) is from the eminently readable Probability in Quantum Theory by E.T. Jaynes, which presents a critique and alternative perspective on the role of probability within quantum mechanics. If you've any interest in philosophy of science or the philosophical disputes between frequentism and Bayesianism, even if you've no real knowledge of physics, then I highly recommend reading it. While the frequentist vs Bayesianist argument is well-known of, the details of what is actually at stake are less well-known and often quite subtle. I think the author does a good job of bringing out and highlighting what the argument is about, and why it is relevant to the future of science (especially physics).

For my part, I've been well indoctrinated into the Bayesian philosophy. This semester I'm taking a course on frequentism, or rather on "experimental methods" as they call it. A professor here has been pushing hard for Bayesian methods in behavioral sciences, and the professor of my class delights in teasing him about it (though he admits to no investment in the philosophical debate). It's been a very long time since I've seen the frequentist perspective, and I'm always of the opinion that it's good to keep an eye on one's philosophical enemies. I've known that frequentism has long dominated the behavioral sciences, but I must shamefully admit that I've attributed this to them being "soft" (even for as much as I identify with my undergrad training in anthropology and humanities). However, coming from machine learning where Bayesianism is de rigueur, one thing I found startling about the article is that, apparently, in physics too it's the frequentists who've dominated the conversation for decades. Indeed, as Jaynes portrays it, it's the frequentists who ousted Laplace, rather than the other way around as is portrayed in AI/ML circles.

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.