Reaction time in relation to display size and correctness of response in forced-choice visual signal detection

Response times were recorded in a two-alternative, forced choice visual detection situation. Stimulus displays, presented tachistoscopically, were randomly selected consonant letters distributed in random subsets of cells of a matrix. Display sizes in Experiment 1 were 8, 12, and 16 letters; in Experiment 2—1, 4, and 8 letters; on each trial S operated a key to indicate which member of a predesignated pair of letters (signal elements) was present in a given display. Correct response times, on the average, increased uniformly with display size. Incorrect response times were uniformly greater than correct response times and, except for a reduction in the case of one element displays, were constant over display size. These relationships appear to require a modification of one assumption in the earlier proposed serial processing model for tachistoscopic perception.