The joint contributions of shape and color to variability discrimination

Abstract

Two experiments examined college students’ discrimination of complex visual displays that involved different degrees of variability or “entropy.” Displays depicted 16 line drawings of various shapes and colors; the participants needed to learn to classify a display in terms of its variability in shape or color while discounting variability in the other dimension (Experiment 1), or to classify based on both shape and color variability (Experiment 2). The participants’ accuracy and reaction time scores on a two-alternative forced-choice discrimination disclosed that people can learn to discount variability in an irrelevant dimension when necessary, but this variability does affect performance. Our data further suggest that variability discrimination depends on degrees of similarity across multiple dimensions thus underscoring the shortcomings of a measure of categorical variability (e.g., entropy) that only considers whether items are identical or different.