Reaching Distance Influences Perceptual Decisions

Decision making is an integral part of everyday life. Recently, there has been a growing interest in the potential influence of action on perceptual decisions, following ideas of embodied decision making. Studies examining decisions regarding the direction of noisy visual motion have found a bias towards the least effortful response option in experiments in which the differences in motor costs associated with alternative response actions were implicit, but not in an experiment in which these differences were made explicit. It remains unclear whether the biasing effect generalizes to other perceptual tasks than motion perception and whether consciously experiencing motor costs prevents such biases. To test the generalizability of effects across perceptual tasks, we used a within-subjects design where 24 participants performed both a motion discrimination task and an orientation discrimination task. Motor costs were manipulated by presenting response buttons for the two alternative choices at different reaching distances. By varying distances randomly, we avoided implicit biases linked to specific decisions. Our findings revealed a bias towards closer response options in both tasks, indicating that explicit information of motor costs significantly impacts perceptual decisions beyond motion discrimination. Contrary to prevailing theories that consider the motor system as a mere effector of the decision, our study implies that the actions that are associated with the response options influence the decision process itself.