Psychic powers proved by research! Also, man flies on unicorn!

Jerry Coyne, over at his blog Why Evolution Is True, mentions the imminent publication of a study that purports to demonstrate evidence for precognition:
A respected peer-reviewed journal in psychology, The Journal of Personality and Social Psychology, is about to publish a paper that presents scientific evidence for precognition.  The paper, by Daryl Bem of Cornell University, is called Feeling the future: Experimental evidence for anomalous retroactive influences on cognition and affect,” and you can download a preprint on his webpage.  I’ve scanned the paper only briefly, and am posting about it in hopes that some of you will read it carefully and provide analyses, either here or elsewhere.
The paper purports to show that a choice that you make in a computer test can be influenced by stimuli you receive after you’ve already made the choice.  This implies you have some way, consciously or unconsciously, of detecting things that haven’t yet happened.
There's a disturbingly enthusiastic report on the study over at Psychology Today which claims, fudgingly (yes, I'm making up a word), that this is not only totally valid research but fits with what we know about... wait for it... quantum mechanics:
... modern quantum physics has demonstrated that light particles seem to know what lies ahead of them and will adjust their behavior accordingly, even though the future event hasn't occurred yet. For example, in the classic "double slit experiment," physicists discovered that light particles respond differently when they are observed [...] But in 1999, researchers pushed this experiment to the limits by asking "what if the observation occurred after the light particles were deployed." Surprisingly, they found the particles acted the same way, as if they knew they were going to be observed in the future even though it hadn't happened yet.
So what does a skeptic like me make of all this? First let's talk about the Psychology Today article, because the author gets her quantum mechanics wrong. Stephen Hawking talked about these experiments, called "delayed choice experiments", in The Grand Design. In the classic double-slit experiment in quantum mechanics, a particle shot through two slits as they go toward a detection screen can be observed to form an "interference pattern" at the detection screen which suggests, bizarrely, that the particle went through both slits simultaneously. This became the root of Richard Feynman's "sum over histories" methodology for calculating the probability of a particle's path, which agrees with the interference pattern we observe at the detection screen.  Feynman concluded that a particle does not take a single path from point A to B (in which the double slit lies between A and B), but all possible paths.

So here's the really weird thing. Contrary to the above article, all observations of the particles occur after they are deployed – the difference is at what point they're observed. If they're observed as they moved through the double slit, we can choose to observe one slit or the other to see which slit a particle goes through (called which-path information), and when we have this information, the interference pattern will not form. But if we do what is called a delayed-choice experiment, in which we don't observe the particles until after they've passed through the double slit but just before they hit the detection screen, the data is the same as when we choose to observe (or not observe) the which-path information by watching the slits themselves. This is counter-intuitive because even if we didn't have the which-path information, we would think that we could determine which slit a particle went through, but that's not the case – a particle still takes all possible paths and, if we don't observe the which-path information, we still get an interference pattern even if we observe the particle after it presumably would have had to go through one slit or the other.

The implication of delayed-choice experiments is not that particles are psychic, as the author suggests, but that in quantum mechanics, the universe has not one single history but all possible histories. Like the future, the past exists as a spectrum of possibilities.

As usual, I'm more than a little annoyed though when people attempt to extrapolate the bizarre world of subatomic particles to everyday research in order to explain strange results. I think that it's much more likely that this experiment is simply a fluke. I'm not equipped to analyze the research methodology, but I think an extra measure of skepticism is warranted in cases where researchers claim to have found scientific evidence for supernatural or psychic phenomena. Others with expertise in the field are already dissecting and criticizing the experiment, but for my part, it's only important to point out that no scientific question is settled from a single experiment, even if it gets published. Many bad studies get published, and some studies are even retracted years later.

The real measure of this experiment will be whether it can be replicated again and again by other researchers, the way the double-slit and delayed-choice experiments have. Based on the dubious history of psychic research, I'm hedging my bets that this will be much ado about a flawed and ultimately irrelevant experiment.


  1. I'm always amazed at the use of quantum mechanics' description of the behavior of microscopic objects to describe behavior of macroscopic objects. The probability of certain behaviors becomes so small as to be negligible in the macroscopic world to the point of aligning with classical mechanics. I'm surprised they actually published this in Psychology Today.


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