annals of very large effect sizes

From Nicholas Kristof’s most recent column in the NYT:

Researchers once showed people sketches of a white man with a knife confronting an unarmed black man in the subway. In one version of the experiment, 59 percent of research subjects later reported that it had been the black man who held the knife.

Does anyone know the study on which this is based?

Author: jeremy

I am the Ethel and John Lindgren Professor of Sociology and a Faculty Fellow in the Institute for Policy Research at Northwestern University.

6 thoughts on “annals of very large effect sizes”

  1. I wondered this too… Seems to come from: Allport, G. W., & Postman, L. J. (1947). The psychology of rumor. New York: Russell & Russell, according to this article:

    Click to access pob5.pdf

    I’ll confess to not having immediate access to the book, so this info could be wrong…


  2. Found it. Julian CW Boon and Graham M Davies, Canadian Journal of Behavioral Science 19 (4) 1987 “Rumours greatly exaggerated: Allport and Postman’s apocryphal study” summarizes the original experiment and then the way it was misinterpreted by Buckhout ‘s paper on eyewitness testimony. Their article replicates the study with a lot more methodological details and does find a stereotype effect on memory that is mediated by context.

    Originals are Allport & Postman 1945 “The basic psychology of rumor,” Transactions of the New York Academy of Sciences 8, 61-81 and (as cgishipster says) 1947 The Psychology of Rumor.

    In poking around, I also found a meta-analysis that finds that the presence of a weapon in a crime scene increases errors of identification.

    Liked by 1 person

  3. OW (or any other scatterplotters) — have you ever tried a simplified version of the Boon / Davies experiment in an undergraduate class, as a teaching tool? Seems like it’d be pretty easy in the age of PP and clickers: show the slide at the beginning of a class session, ask for recall at the end. If you had different groups of students, you could play around with variations in the content of the intervening lecture: e.g., unrelated to race, related to race but not to criminal justice, or related to racial disparities in the CJ system.

    Hmm, maybe I’ll try it myself, next time I teach intro.

    Liked by 1 person

    1. This would be great. I keep stalling on adopting any kind of clicker approach because it isn’t standardized on my campus and the overhead of first adoption keeps being a hurdle. But I agree with you, this is the perfect kind of thing to do in a classroom exercise. I have heard tales of profs who stage a disruption in the classroom (actors come in unexpectedly and do something) and then give quizzes on what happened, to demonstrate the unreliability of eyewitness testimony.


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