Human movement initiation: Specification of arm, direction, and extent.

Abstract

Presents a method for discovering how the defining values of forthcoming body movements are specified. Information is given about some, none, or all of the defining values of a movement that will be required when a reaction signal is presented. It is assumed that RT reflects the time to specify those values that were not precued. With RTs for the same movements in different precue conditions, it is possible to make detailed inferences about the value specification process for each of the movements under study. The present experiments were concerned with the specification of the arm, direction, and extent (or distance) of aimed hand movements. In Exp I (10 university students) it appeared that (a) specification times during RTs were longest for arm, shorter for direction, and shortest for extent; and (b) these values were specified serially but not in an invariant order. Exp II (6 Ss) suggested that the precuing effects obtained in Exp I were not attributable to stimulus identification. Exp III (8 Ss) suggested that Ss in Exp I did not use precues to prepare sets of possible movements from which the required movement was later selected. The model of value specification supported by the data is consistent with a distinctive-feature view, rather than a hierarchical view, of motor programming. (60 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)