Hemispheric differences in simple reaction time to auditory stimuli of different frequencies.

To determine whether reaction time varies as a function of tone frequency and/or ear stimulated 27 adult subjects were presented with two two-tone series (1,000 Hz vs 2,500 Hz and 1,500 Hz vs 4,000 Hz) in a simple reaction-time paradigm. The analyses clearly indicated that the higher tone in each series and stimulation to the right ear resulted in significantly shorter reaction times. These results were interpreted as indicating that cerebral asymmetries are apparent in tasks and with stimuli that do not seem to require higher-order inferences regrading the functional organization of the cerebral hemispheres.