Negative and positive incentive contrast in humans with males vs females, monetary reinforcement, and reaction time

Abstract

Negative incentive contrast effects which were obtained for male human subjects by a reduction in the quantity of monetary incentives in a simple reaction time task failed to appear in female subjects. In a second experiment, male human subjects displayed positive contrast effects after an upshift in reward magnitude, while females failed to exhibit positive incentive contrast effects. While it appears that sex is a determiner of human incentive contrast effects, the present studies increased the generality of the observation of incentive contrast (1) from infrahumans to humans, and (2) from mental multiplication tasks with nonmonetary reinforcement to a reaction time task with monetary reinforcement.Negative incentive contrast is obtained when, consequent to a decrement in reward, quantity performance level falls significantly below the level of responding of a control group which continuously receives the smaller amount of reward; positive contrast effects occur when an increase in incentive magnitude produces a reliably higher level of performance than the performance level of control subjects. While it is somewhat less than realistic to suggest that the variables which control the occurrence of these phenomena in animals have been determined, it is even less clear what factors determine contrast effects at the human level. In general, in investigations involving infrahuman organisms, the further one departs from a paradigm of a continuous schedule of reinforcement, solid food reward, and large changes in reward magnitude, the less likely are contrast effects to occur. That is to say, schedule, solidity of reinforcement, and magnitude of incentive change appear to be some of the variables which control incentive contrast effects in animals. At the human level, age, amount of pre shift training (e.g., Weinstein, 1972), and magnitude of reward change (e.g., Weinstein, 1970) are three of the very few factors that have been found to control the effects. No studies have examined the role that sex might play in producing contrast effects with animal or human organisms. Experiment 1 attempted to ascertain how male and female human subjects respond to a reduction in the amount of monetary reward in a typical simple reaction time task. Experiment 2 attempted to determine how human subjects of both sexes react to an increase in quantity of monetary incentive in the characteristic reaction time situation.