Individual differences in visual comparison processes

Two experiments are reported in which subjects compared the shape of two successively presented random visual forms. The first stimulus in the pair was one of five “standard” shapes, and the second stimulus was either the same as the standard or different by virtue of a perturbation in shape or an overall reflection. Marked individual differences were found in reaction time for the same-different comparison. For one type of subject “same” responses were faster than “different” responses, speed of “different” responses was unaffected by similarity of the test shape to the standard, and error rates and reaction times were not systematically related. For the other type of subject, “different” responses were generally faster than “same” responses, “different” reaction time decreased as the standard shape and the test shape became increasingly dissimilar, and error rates and reaction times were positively correlated. Implications of these individual differences for models of the same-different comparison process are discussed.