Date of Award


Document Type


Degree Name

Master of Arts (MA)




In this experiment differential hemispheric processing demands in four cognitive tasks, two verbal and two non-verbal, were measured using a simple reaction time probe procedure. The procedure also measured the interference between the reaction time probe and the verbal and nonverbal tasks. The method used was similar to that found in information processing research using a concurrent task procedure to measure processing demands during primary task performance (Posner & Boies 1971). In the concurrent task procedure the subject is requested to perform two tasks at the same time: a cognitive (primary) task and a reaction time probe (secondary task). The accuracy and speed of response to the unpredictable perceptual probe is used as a measure of spare capacity during the performance of the primary task that is available to be allocated to perceptual monitoring at the instant of probe presentation.

Four primary tasks were designed considering previous laterality research findings: two left hemisphere primary tasks (one requiring visual word processing and one requiring auditory word processing) and two right hemisphere primary tasks (one requiring visual-spatial processing and one requiring tone processing). Response to the primary task was pressing a switch with the right or left foot. The reaction-time probe tasks consisted of responding to stimuli presented to the right hemisphere with the left hand and stimuli presented to the left hemisphere with the right hand. The subjects responded to 26 randomly presented reaction time probes equally divided between right and left presentations. Twelve males and twelve female subjects served in each modality. Each of the tasks was performed alone and concurrently. The subject was instructed to pay equal attention to both tasks.

Results showed that the male subjects tended to have shorter response latencies to the auditory reaction-time probes and female subjects tended to have shorter response latencies to the visual reactiontime probes. In addition, males had faster response latencies when the visual probe was presented to the right hemisphere than the left. These data suggest that males and females differed in the subprocesses they used to perform these tasks, and that visual and auditory subprocesses are organized differently within the sexes.

Results during concurrent performance in the auditory activation task condition showed that the right foot interfered more with right hand performance and the left foot interfered more with left hand performance. These data suggest that the major source of interference between the activation task and criterion task was interference between motor components of the two tasks.

Major differences were found between the verbal and non-verbal primary tasks in the way they were time-shared with the probe task. Performance on the verbal primary tasks appeared to have priority over the reaction time probe while performance on the non-verbal primary tasks did not; performance on the verbal primary tasks improved during concurrent conditions and performance on the non-verbal primary tasks declined. The enhancement in performance on the verbal primary tasks was accompanied by a greater decrement in performance on the probe task than occurred for probes during the non-verbal primary tasks.