JUDGMENTAL CONTRAST EFFECTS IN RELATION TO RANGE OF STIMULUS VALUES

Examined the occurrence of judgmental contrast effects in relation to the range of stimuli experienced by experimental and control groups. Exp. I assessed the response function for a series of random black-and-white checkerboard patterns where the proportion of black squares ranged from .2-.8 and 15 undergraduates judged the amount of black area. Exp. II was a 3 * 3 factorial involving preshift and postshift combinations of either a light, medium, or dark series, using 117 undergraduates. Positive and negative contrast effects were obtained in the postshift stage. A reduction of the slope of the postshift response functions was also demonstrated. Exp. III with 39 high school students as control groups experienced the same range of preshift and postshift stimulus values as each shifted group in Exp. II, but under nonshift conditions. The contrast effects obtained in Exp. II were contingent on reduction of the slope of the postshift response functions associated with the greater range of stimulus values experienced by the shifted groups. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.