Influences of Hemispheric Specialization and Interaction on Task Performance

138 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.The goal of the present research is to investigate the factors that influence the degree to which dividing information processing between the cerebral hemispheres improves performance. The research in this dissertation provides evidence that dividing processing between the cerebral hemispheres improves performance when a task is computationally complex, but only to the extent that the operations required by the task can be divided between the hemispheres.Following on previous findings (Banich and Belger, 1990), subjects were tested on a series of tasks varying in computational complexity. These tasks included letter matching tasks, which can be performed by either hemisphere, and a rhyme task, which requires the left-hemisphere's processing capabilities. Complexity of the letter-matching tasks was manipulated by either increasing the number of inputs to be processed or by the number of steps required by the decision. The results indicated that the advantages of between-hemisphere processing increased as a function of task complexity during the letter-matching tasks regardless of the manipulation, but between-hemisphere division of processing did not improve performance during the rhyme task, despite its complexity. These findings indicate that task characteristics may limit the advantages of between-hemisphere information processing.Furthermore, individual differences in hemispheric utilization biases were also found to have significant effects on the ability to divide processing between the hemispheres. These effects were such that when task demands and hemispheric utilization biases both loaded on the same hemisphere, such as a left-hemisphere utilization bias during the performance of the rhyme task, the ability to divide the processing between the hemispheres was limited. This finding was observed only for right-handed individuals.In sum, this research presents evidence that interhemispheric processing improves performance at higher levels of task complexity when the operations required by a task can be divided between the hemispheres.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD