Effect of irrelevant differences as a function of the relations between relevant and irrelevant dimensions in the same-different task.

The effects of irrelevant differences as a function of the relations between relevant and irrelevant dimensions in the same-different task were examined. Form, size, and orientation were used as task conditions in Experiment 1, and form, size, and color were used in Experiment 2. In each experiment, 6 subjects were instructed to report same or different according to a relevant dimension, irrespective of two irrelevant dimensions. In Experiment 3, the degree of integrality was examined in all the combinations of dimensions involved, in the restricted-classification task. The results of the three experiments suggested that (a) effects of irrelevant differences depended on the degree of integrality between relevant and irrelevant dimensions, and (b) two irrelevant dimensions were processed by the subjects serially. Neither the relevance rechecking model (Miller & Bauer, 1981) nor the response competition model (e.g., Williams, 1974) alone could explain all the types of effects of irrelevant dimensions obtained in this study. Instead, a modified relevance rechecking model, in which the degree of integrality was introduced to the original relevance rechecking model, could predict and explain all types of effects.