Letter matching in the hemispheres: speed-accuracy trade-offs.

Eight subjects performed physical and nominal letter-matching tasks for pairs of letters presented in the left, right, or central visual fields, using a unimanual two-choice response-time paradigm. Latencies were manipulated by using a cued response procedure, and speed-sensitivity and speed-bias functions were calculated separately for each of the peripheral visual field by response hand conditions. Hemispheric contributions to these tasks were investigated by looking for evidence of exclusive specialization and callosal transfer. The results suggest that both hemispheres are able to perform the tasks and that they do so using similar processing strategies, but they differ in the response-choice stage of the nominal identity task.