COSTS AND BENEFITS OF INTEGRATING INFORMATION BETWEEN THE CEREBRAL HEMISPHERES - A COMPUTATIONAL PERSPECTIVE

Because interaction of the cerebral hemispheres has been found to aid task performance under demanding conditions, the present study examine d how this effect is moderated by computational complexity, the degree of lateralization for a task, and individual differences in asymmetri c hemispheric activation (AHA). Computational complexity was manipulat ed across tasks either by increasing the number of inputs to be proces sed or by increasing the number of steps to a decision. Comparison of within- and across-hemisphere trials indicated that the size of the be tween-hemisphere advantage increased as a function of task complexity, except for a highly lateralized rhyme decision task that can only be performed by the left hemisphere. Measures of individual differences i n AHA revealed that when task demands and an individual's AHA both loa d on the same hemisphere, the ability to divide the processing between the hemispheres is Limited. Thus, interhemispheric division of proces sing improves performance at higher levels of computational complexity only when the required operations can be divided between the hemisphe res.