Probabilities and utilities of fictional outcomes in Wason's four-card selection task.

Four experiments are presented that show that selections in Wason's (1966) four-card selection task can be increased by increasing the probability that cards will yield important outcomes. Experiment 4 also shows that selections can be influenced by varying the utilities of possible outcomes. These results suggest that some important content effects in this task may not arise from inferential processes, and examples are given of how probabilities and utilities have been confounded with other manipulations in previous research. The recent trend towards content-dependent theories of reasoning may have arisen largely because theorists are attempting to construct models of inferential reasoning that can account for what are, in part, non-inferential phenomena. Content-independent inferential processes and content-independent choice processes may operate together to account for content effects in the selection task.

Heroin addicts have higher discount rates for delayed rewards than non-drug-using controls.

Fifty-six heroin addicts and 60 age-matched controls were offered choices between monetary rewards ($11-$80) available immediately and larger rewards ($25-$85) available after delays ranging from 1 week to 6 months. Participants had a 1-in-6 chance of winning a reward that they chose on one randomly selected trial. Delay-discounting rates were estimated from the pattern of participants' choices. The discounting model of impulsiveness (Ainslie, 1975) implies that delay-discounting rates are positively correlated with impulsiveness. On average, heroin addicts' discount rates were twice those of controls (p = .004), and discount rates were positively correlated with impulsivity as measured by self-report questionnaires (p < .05). The results lend external validity to the delay-discounting rate as a measure of impulsiveness, a characteristic associated with substance abuse.

Delay-discounting probabilistic rewards: Rates decrease as amounts increase.

The independence of delay-discounting rate and monetary reward size was tested by offering subjects (N = 621) a series of choices between immediate rewards and larger, delayed rewards. In contrast to previous studies, in which hypothetical rewards have typically been employed, subjects in the present study were entered into a lottery in which they had a chance of actually receiving one of their choices. The delayed rewards were grouped into small ($30-$35), medium ($55-$65), and large amounts ($70-$85). Using a novel parameter estimation procedure, we estimated discounting rates for all three reward sizes for each subject on the basis of his/her pattern of choices. The data indicated that the discounting rate is a decreasing function of the size of the delayed reward (p < .0001), whether hyperbolic or exponential discounting functions are assumed. In addition, a reliable gender difference was found (p = .005), with males discounting at higher rates than females, on average.

Making choices in anticipation of similar future choices can increase self-control.

Two experiments tested the efficacy of linking a current choice with similar future choices as a means of increasing self-control. Participants were offered choices between smaller and sooner vs. larger and later amounts of money (Experiment 1, n = 60) or food (Experiment 2, n = 34). After a small-large pair for which the participant preferred the smaller reward was found, a choice between the same pair was offered as the 1st of 5 such choices to be offered over a period of weeks. The majority of participants in both experiments who chose between all 5 smaller and all 5 larger rewards chose the larger rewards. One third of participants in Experiment 1 who could choose independently on each pair in the series reversed their previous preference and chose the larger reward in the context of the series. These results suggest that self-control can be enhanced by viewing one's current choice as predictive of future choices.