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Archive for September 28th, 2011

53.1%: Precognition or Statistical Fluke?

Posted by The Situationist Staff on September 28, 2011

From The Epoch Times, here are some excerpts from an excellent summary of Daryl Bem’s intriguing research on precognition and reactions to that research:

Social psychologist Daryl Bem of Cornell University created quite a buzz in the field of parapsychology last year when he claimed he had evidence that future events can reach back in time to affect a person’s behavior.

. . . [B]elievers and cynics had already been fussing over his findings and debating the general existence of psi, the umbrella term for any process of information or energy transfer that is inexplicable with currently known physical or biological principles.

In the paper, Bem details nine experiments that he led, all involving well-established procedures utilized in the field of social psychology. The critical point, however, was that Bem “time-reversed” the procedures, meaning that instead of exposing participants to a stimulus (usually considered the cause of a person’s behavior) and then measuring the reaction (the effect), Bem recorded participants’ behaviors first and then supplied the stimuli.

In Bem’s first experiment, the major focus point of mass media, participants were presented with an image of two curtains on a computer screen and asked to guess which curtain was concealing a picture. In actuality, the image and its position were only determined by the computer’s randomization program after the participant made his decision.

“From the participants’ point of view, this procedure appears to test for clairvoyance,” according to the article. “In fact, however, neither the picture itself nor its left/right position was determined until after the participant recorded his or her guess, making the procedure a test of detecting a future event (i.e., a test of precognition).”

Bem found that in cases where the computer had later generated an erotic image, participants had guessed the correct position 53.1 percent of the time. Although small, the difference between his finding and 50 percent (the expected percentage of correct guesses based purely on chance), is statistically significant, argued Bem, which suggested that, overall, participants’ correct guesses were at least partially due to something other than chance.

Across seven of his other eight experiments, Bem obtained similar data supporting the existence of psi. Skeptics, however, have raised the concern that Bem’s anomalous findings are merely statistical flukes.

In a critique published alongside Bem’s article, Eric-Jan Wagenmakers and his colleagues at the University of Amsterdam advocated for a more “conservative” statistical test to evaluate Bem’s data. According to their analysis, the majority of Bem’s experiments actually provided either “anecdotal” or “substantial” evidence in favor of the non-existence of precognition.

However, at the same time, they did find that three of Bem’s experiments provided “anecdotal” justification of his claims, and that the results of his ninth experiment were “substantial.”

Bem’s ninth experiment tested for “retroactive facilitation of recall.” Participants were shown 48 nouns one at a time, and then told to type as many of the words as they can recall. Half of the words were randomly selected by the computer and displayed to the participants one at a time again. Next, the same subset of words were presented altogether while the participant had to click on the words to place them into categories and type them.

The point was to see if this future exposure and practice trials of typing the subset of words would correlate with higher recall of the selected words at the expense of the non-selected words. Bem concluded that his results support psi phenomenon, and even Wagenmakers found that the results were “substantial.”

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Stephen Colbert interviews Daryl Bem:

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From ABC News:

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Related Situationist posts:

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