Abstract
College students learned to earn points by categorizing binomial samples produced by two equally likely and complementary random processes. To facilitate cross-species comparisons, the procedure was made to resemble an experiment with pigeon subjects (Shimp & Hightower, 1990). Samples were 1, 2, 4, or 8 successively presented outcomes (vertical or horizontal lines) of, in effect, tossing one of two equally likely coins, one coin (A) biased in favor of vertical and the other coin (B) similarly biased in favor of horizontal. Choosing red or green stimuli presented after each sample was reinforced if coin A or B had been tossed, respectively. The statistical diagnosticity of a sample, the relative likelihood of its having been produced by a particular coin, was varied by the bias on the coins and by sample size. Subjects became more conservative in the use of statistical information in a sample as the average diagnosticity of other samples (due to the bias on the coins) decreased. Except for this “irrational” context effect, the results qualitatively resembled those in the corresponding experiment with pigeons.
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This research was supported in part by the Biomedical Sciences Support Grant Committee of the University of Utah and by NIMH Grant RO1 MH 42770 to the second author.
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Kent Parker, B., Shimp, C.P. Intuitive statistical inference: An “irrational” context effect in college students’ categorization of binomial samples. Bull. Psychon. Soc. 29, 411–414 (1991). https://doi.org/10.3758/BF03333956
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DOI: https://doi.org/10.3758/BF03333956