Improved temporal stability in multieffector movements.

Abstract

Four experiments compared the temporal stability of actions involving either 1 or more effectors. A reduction in within-effector temporal variability was observed during 2-effector tapping relative to when either effector moved alone. This phenomenon was observed for various limb combinations, and it did not require that the timed movements be produced in a repetitive manner. Moreover, an additional reduction in variability was found when tapping involved 3 effectors. This multiple effector advantage was multiplicative: The magnitude of the advantage was greater for longer target intervals. It is proposed that independent temporal representations are generated for each effector. These representations are integrated to produce coordinated motor commands, and the multiple effector advantage is a statistical consequence of the integration process.