Temporal Patterning in Choice among Delayed Outcomes

Undergraduates chose repeatedly between two equal monetary outcomes. One outcome was more immediate, but the other resulted in less delay on future trials and a lower average delay per outcome overall. Minimizing average delay per outcome maximized overall reinforcement rate (money earned). The difference in immediacy between the two alternatives on a given trial was easily perceptible but the (opposed) difference in overall reinforcement rate was gradual and difficult to perceive. Subjects frequently chose the more immediate outcome and thus failed to maximize overall reinforcement rate. However, when choice-outcome (CO) units were grouped in triplets (as opposed to being presented singly at fixed intervals) subjects chose the more immediate outcome less often and thereby increased overall reinforcement rate. Findings are discussed in terms of impulsiveness and risk-aversion in laboratory studies and in everyday life.