Stimulus-response compatibility for left-right discriminations as a function of stimulus position.

In two experiments, choice response times to visual stimuli (word and arrow) were measured. The stimuli were presented briefly (180 msec) in left and right visual half-field (VHF). Each stimulus required a left-right discrimination; however, half the stimuli were positive (e.g., LEFT), and half were negative (e.g., NOT RIGHT). In Experiment 1, button-pressing responses in the midsagittal plane were used; in Experiment 2, vocal responses were used. There was a strong stimulus-response (S-R) compatibility effect, influenced by the interaction of negation (positive vs. negative) and stimulus position (VHF). Latencies were faster to positive stimuli whose direction and VHF matched than to positive stimuli whose direction and VHF did not correspond. Conversely, latencies were faster to negative stimuli when response direction and VHF did not match than when direction and VHF did correspond. These results replicate the S-R compatibility effect found by Whitaker (1980) using foveal stimuli. The results were analyzed with regard to a hemisphere activation model proposed by Cotton, Tzeng, and Hardyck (1980) but were found to fit Whitaker's (1980) model better.