EFFECTS OF DECISION CRITERION ON RESPONSE LATENCIES OF BINARY DECISIONS

The effects of decision criterion on response latencies of binary deci sions were examined. The stimuli comprised two, partly overlapping, '' normal'' distributions of either two-digit numbers or tonal frequencie s. Individual stimuli were randomly sampled from the distributions, an d subjects had to decide from which distribution the stimulus was samp led. The decision goal was to maximize the expected gain using three d ifferent payoff matrices. Decision latencies with and without prior kn owledge of optimal decision criteria were measured. In a control task, subjects were asked only to label stimuli as being either above or be low the optimal criteria (without regard for a posteriori probabilitie s or expected gain). The relation between criterion and latency was ex amined by means of a trial-by-trial analysis of the stimuli and the re sponses. Response latency was inversely related both to the distance b etween the stimulus and the decision criterion and to the probability of the response elicited by the stimulus. Response latencies showed a maximum at the criterion in all conditions. These results were obtaine d with different stimulus modalities (tones or numbers), different dis criminability levels within the auditory modality, and different decis ion tasks. It is proposed that the decision criterion is the primary d eterminant of response latencies of binary decisions.