Choice of modes of action and intrinsic metric in an arm reaching task [Elección de modos de acción y métrica intrínseca en una tarea de alcance con el brazo]

Abstract

Two groups of participants, men and women, reached in seated position for a plastic block that was presented on a table at different distances. When the distance was expressed in extrinsic units (centimeters), women changed their modes of action for reaching for the block at closer distances than men because their body sizes were smaller than those of men. When the distance was expressed in intrinsic units; that is, as the ratio between the distance of the block and the arm length of each participant, both men and women allocated their modes of action to reach for the block in a comparable way along the different distances. However, at the π distance 1.1 differences were observed in the performance of men and women. The choice of mode of action shifted in critical points where the relationship between the distance of the block and arm length induced the appearance of a different mode of action. The choice of the mode of action varied more at and at distances around the absolute critical boundary of the arm-only mode of action. These findings suggest that the relation between the subject’s body scale, his or her biomechanical restrictions, and the scale of the environment, contributes to the choice of mode of action. © 2013, Sociedad Mexicana de Analisis de la Conducta. All rights reserved.