Interference effects of verbal and spatial tasks on simple visual reaction time.

Simple reaction times to lateralized light flash stimulation were measured in normal right-handers either with or without a concurrent task. In agreement with a previous report, a counting backwards task resulted in a substantial RT slowing which affected right-side stimuli more than left. Contrary to expectation, however, a tactual orientation discrimination task resulted in RT slowing which affected right-hand responses more than left, with no visual asymmetry.