Stimulus modality and stimulus-response compatibility in absolute identification

Accuracy and response time (RT) were measured in the absolute identification (Al) of ten unidi-mensional perfectly pairwise discriminable stimuli. One group of 20 subjects performed a visual AI task involving line segments of variable length. A second group of 20 subjects participated in an auditory task with the stimuli composed of pure tones of variable intensity. Subjects performed the task under two conditions: a spatially compatible and a spatially incompatible stimulus-response mapping. Results showed greater accuracy for the visual modality and longer RT for the incompatible mapping. The experimental factors did not substantially alter the bowing observed when performance was plotted according to the ordinal position of the stimuli. The data do not support the hypothesis that the bow effect is attributable to motor programming or motor adjustment stages.