Decision latencies of "same" and "different" judgments

Abstract

When a subject is asked to judge whether two stimuli are "same" or"different," the time he takes to reach the decision same is frequently unequal to the time he takes to reach the decision different. We studied this discrepancy as a function of several variables, including stimulus modality, "codability" vs."noncodability" of test stimuli, interstimulus interval, and discrimination difficulty. Results of four different experiments performed on a total of 111 subjects showed codability and discrimination difficulty to be the most important factors. Stimuli that are codable (i.e., which can be categorized by absolute judgment) yield a shorter latency for decision same, and noncodable stimuli (i.e., those requiring a reference stimulus for categorization) yield a longer latency for decision same. The modality of test stimuli, the prothetic or metathetic nature of the dimension to be judged, and simultaneous vs. successive presentation of the stimuli appear not to be crucial factors. © 1968 Psychonomic Society, Inc.