Abstract
Numerous psychophysical studies suggest that the sensorimotor system chooses actions that optimize the average cost associated with a movement. Recently, however, violations of this hypothesis have been reported in line with economic theories of decision-making that not only consider the mean payoff, but are also sensitive to risk, that is the variability of the payoff. Here, we examine the hypothesis that risk-sensitivity in sensorimotor control arises as a mean-variance trade-off in movement costs. We designed a motor task in which participants could choose between a sure motor action that resulted in a fixed amount of effort and a risky motor action that resulted in a variable amount of effort that could be either lower or higher than the fixed effort. By changing the mean effort of the risky action while experimentally fixing its variance, we determined indifference points at which participants chose equiprobably between the sure, fixed amount of effort option and the risky, variable effort option. Depending on whether participants accepted a variable effort with a mean that was higher, lower or equal to the fixed effort, they could be classified as risk-seeking, risk-averse or risk-neutral. Most subjects were risk-sensitive in our task consistent with a mean-variance trade-off in effort, thereby, underlining the importance of risk-sensitivity in computational models of sensorimotor control.
Highlights
In the fields of psychology and economic decisionmaking, it is well established that risk attitudes influence human behaviour
Nagengast et al [29] showed that subjects exhibit risk-averse behaviour in a motor task that required them to control a Brownian particle under different levels of noise
Comparing the cumulative prospect theory (CPT) model to the mean-variance model, we found that the mean-variance model was preferred both based on Bayesian information criterion (BIC) and based on Akaike information criterion (AIC)
Summary
In the fields of psychology and economic decisionmaking, it is well established that risk attitudes influence human behaviour. Nagengast et al [29] showed that subjects exhibit risk-averse behaviour in a motor task that required them to control a Brownian particle under different levels of noise.
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