Reaction Times and Response Competition between the Right and Left Hands

Abstract

If subjects are required to make two responses at the same time, one with each hand, the responses of the hand appearing second in this sequence may be considerably delayed. The hands appear to be in competition with one another for first response. Interference of this kind was studied in an experiment in which, interspersed in a series of signals for either right or the left hand response, were a number of double signals which called simultaneously for response from both hands. Both the right and the left hands had an equal chance of taking precedence over the other, and an equal chance that their response would be delayed. The hand controlled by the dominant hemisphere responded first no more often than did the non-dominant one. A degree of synchrony developed between the responses of the hands as the subject experienced a greater number of signals for paired response. In a second experiment the hands were required to compete with one another after practice had been given in responding with only one hand. The effects of practice were not equal and opposite across the body. Practised left hand responses were found not to be disturbed by the addition of a simultaneous signal for another response, whereas right hand responses were. This relationship exists in both right and left-handed subjects, and the results seem to point to differences in cerebral control between the hemispheres which may be related not to handedness but to side of the body as such.