Does risk-sensitivity transfer across movements?

Abstract

An intriguing finding in motor control studies is the marked effect of risk on movement decision making. However, there are inconsistent reports of risk-sensitivity across different movements and tasks, with both risk-seeking and risk-averse behavior observed. This raises the question of whether risk-sensitivity in movement decision making is context dependent and specific to the movement or task being performed. We investigated whether risk-sensitivity transfers between dissimilar movements within a single task. Healthy young adults made arm-reaching movements or whole-body leaning movements to move a cursor as close to the edge of a virtual cliff as possible without moving beyond the edge. They received points on the basis of the cursor's final proximity to the cliff edge. Risk was manipulated by increasing the point penalty associated with the cliff region and/or adding Gaussian noise to the cursor. We compared subjects' movement endpoints with endpoints predicted by a subject-specific, risk-neutral model of movement planning. Subjects demonstrated risk-seeking behavior in both movements that was consistent across risk environments, moving closer to the cliff than the model predicted. However, subjects were significantly more risk-seeking in whole-body movements. Our results present the first evidence of risk-sensitivity in whole-body movements. They also demonstrate that the direction of risk-sensitivity (i.e., risk-seeking or risk-averse) is similar between arm-reaching and whole-body movements, although degree of risk-sensitivity did not transfer from one movement to another. This finding has important implications for the ability of quantitative descriptions of decision making to generalize across movements and, ultimately, decision-making contexts.