NOMINAL AND PHYSICAL DECISION CRITERIA IN SAME-DIFFERENT JUDGMENTS

We propose a model in which the physical and nominal dimensions of let ter pairs are compared independently of whether subjects use physical (shape task) or nominal (name task) identity as the decision criterion . We attempt to explain the fast-same effect, the preponderance of fal se-different errors, and the nominal-physical disparity as results of congruent and incongruent outputs of physical and nominal comparison d evices that function in both tasks. Subjects performed both tasks with and without response deadlines. The stimuli were presented foveally o r unilaterally to one or the other hemisphere. With foveal presentatio ns, the nominal-physical disparity disappeared when congruent and inco ngruent cells were compared, the fast-same effect occurred only in the shape task, and there was a preponderance of false-different errors o nly in the name task. Response times and error patterns from centrally presented trials conformed to the predictions of the model. Performan ce patterns from the lateralized trials conformed only partially. The implications of the data are discussed in the context of several theor etical models of same/different judgments.