An intermanual advantage for tactual matching.

Previous research reports both increased and decreased levels of performance for concurrent tactual tasks when they are carried out by one hand (intramanual condition) rather than shared between the hands (intermanual condition). Intramanual advantages have been attributed to the benefits of intrahemispheric processing which avoids the need for the transcallosal passage of information. Intermanual advantages are attributed to the benefits of sharing the task load between the cerebral hemispheres. The effects of inter- and intramanual activity was investigated in a group of 72 dextrals. Subjects were required to make same/different discriminations for a tactual matching task. Faster completion times were observed for the intermanual condition compared to the intramanual condition. This suggests that the task was carried out more efficiently when the hemispheres shared the processing load. The intermanual advantage was accentuated for judgements of difference which place more strain on processing resources. There was no evidence of a left hand advantage for tactual matching of the type observed for Braille.