Neuringer, A. Jensen, G. & Piff, P. (2007).
Stochastic matching and the voluntary nature of choice.
Journal of the Experimental Analysis of Behavior, 88, 1-28.
Attempts to characterize voluntary behavior have been ongoing for thousands of years. We provide experimental
evidence that judgments of volition are based upon distributions of responses in relation to obtained rewards.
Participants watched as responses, said to be made by ‘actors,’ appeared on a computer screen. The participant’s
task was to estimate how well each actor represented the voluntary choices emitted by a real person. In
actuality, all actors’ responses were generated by algorithms based on Baum’s (1979) generalized matching
function. We systematically varied the exponent values (sensitivity parameter) of these algorithms: some actors
matched response proportions to received reinforcer proportions, others overmatched (predominantly chose the
high-valued alternative), and yet others undermatched (chose relatively equally among the alternatives). In each
of five experiments, we found that the matching actor’s responses were judged most closely to approximate
voluntary choice. We found also that judgments of high volition depended upon stochastic (or probabilistic)
generation. Thus, stochastic responses that match reinforcer proportions best represent voluntary human
choice.
Key words: voluntary behavior, free will, choice, concurrent schedules of reinforcement, psychophysical judgments, humans