The effects of task demands on manual asymmetries in left-handed and right-handed individuals

Abstract

Our work on manual asymmetries has shown that the preferred-hand advantage increases with task complexity in right-handers, but little is known about these effects in left-handers. The purpose of this study was to investigate whether hand differences in performance are affected by task demands in left-handers as they are in right-handers. We tested both left-(n=25) and right-(n=84) handed younger adults on the grooved pegboard task, a measure of fine motor control. As in our previous work, we varied task demands by comparing performance on two phases of this task, the place phase in which participants pick up the pegs from a receptacle and place them into a series of 25 holes and the replace phase which involves removing the pegs from the holes and returning them to the receptacle. Participants performed two trials with each hand on each phase. A 2(hand used) X 2(task) ANOVA on pegboard performance for each handedness group revealed a significant task effect for each group, with the place phase taking significantly longer. For the right-handers there was also a preferred-hand advantage with the right hand taking less time and this preferred-hand advantage was significantly greater for the place phase. Interestingly, however, no hand differences in performance were found for the left-handers nor did task demands affect manual asymmetries in performance. The implications of these findings for understanding the effects of hand preference on manual asymmetries will be discussed.

Acknowledgments: Research support NSERC (PB and ER) and HSFO (ER)