Self-control and choice in humans: Effects of type, amount, and delay of reinforcers

Abstract

The effects of types of reinforcers, relative amounts of reinforcers, and relative lengths of delays upon choice in a discrete-trial button-pressing task were investigated with adult humans. Under conditions with positive reinforcers, subjects chose between periods in which they could produce points, whereas under conditions with negative reinforcers subjects chose between periods in which they could escape from point decrements. Conditions with equal amounts included equal amounts of reinforcers with different delays, whereas conditions with unequal amounts included a larger, more delayed reinforcer and a smaller, less delayed reinforcer. Under conditions with additional delays, a constant delay was added to both delays of conditions without additional delays. Choice proportions for more delayed reinforcers were significantly higher under conditions with unequal amounts than with equal amounts. Negative reinforcers produced significantly lower choice proportions for more delayed reinforcers than positive reinforcers. These results suggested that positive and negative reinforcers might engender different choice.