Light beams for the study of compatibility and crossed-hand effects

Abstract

The crossing of hands increases Manual Reaction Time (MRT) in spatial compatibility tasks. This occurs because the position of the hands has to be first taken into account by the brain before response is executed. This study tested the influence of two parameters on MRT: the position of the effector hand and the location of its projected action, both properly dissociated with the aid of laser pointers. While hands were kept on their respective sides the laser beam was either directed towards the stimulus (compatible condition) or to the opposite side (incompatible condition). Besides, the laser beam could be either directed towards the effector (hand) side or across the midline towards the opposite hemifield (uncrossed and crossed conditions). Our results show both compatibility and crossed effects on MRTs, indicating that spatial interactions occur between the projected action and both the stimulus (compatibility effect) and response key (crossed effect) positions. Keywords: Spatial compatibility; crossed-hand effect; manual reaction time; inhibition; facilitation.