CHOICE IN SELF-CONTROL PARADIGMS USING RATS

Two experiments tested rats' self-control-choice between longer, more delayed access to reinforcement and shorter, less delayed access to re inforcement. Experiment 1 used 8 rats and a discrete-trials procedure in which the reinforcer amounts and delays were held constant througho ut a condition. The rats showed significant impulsiveness. Experiment 2 used 15 rats and a discrete-trials procedure in which the reinforcer delay associated with the self-control alternative was adjusted until each subject was indifferent between the two alternatives. The adjust ed delays were used to estimate subjects' relative sensitivity to chan ges in reinforcer amount versus delay (s(A)/s(D)). Consistent with the results from Experiment 1, s(A)/s(D) was not significantly different from 1.0. Both experiments indicate that in self-control paradigms pre viously used with pigeons and humans, rats are impulsive: Control over their choices by reinforcer delay is at least as strong as control by reinforcer amount.