Biological differences may underlie individual differences in impulsive behavior, such as choice for a smaller, more immediate reinforcer over a larger, more delayed reinforcer. Repeated exposure to drugs of abuse may have differing effects on such behavior. To evaluate acute and repeated effects of nicotine on impulsive choice, two strains of rats that have been shown to differ in impulsive choice were tested in a delay-discounting paradigm. Eight Lewis and eight Fischer 344 rats were allowed to choose between one food pellet delivered immediately and three food pellets delivered after a delay. The delay systematically increased in blocks of trials within each session, and the delay value at which choice for the two alternatives was equal (i.e., the indifference point) was interpolated. Effects of nicotine (0.1 – 1.0 mg/kg, s.c.) on percent choice and indifference points were determined during the acute-testing phase and during the re-determination of effects of each dose following at least 30 sessions of repeated 1.0 mg/kg nicotine exposure. Lewis rats had shorter indifference points (i.e., made fewer larger reinforcer choices) than the Fischer 344 rats. Acute nicotine administration increased mean larger-reinforcer choices at the 0.3 mg/kg dose in the Lewis rats and at the 1.0 mg/kg dose in the Fischer 344 rats. After repeated exposure to nicotine, indifference points returned to near baseline (pre-drug) levels for both strains. Strain differences were observed in rates of delay discounting and nicotine may decrease impulsive choice acutely, but this effect does not appear to be long-lasting.

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Ninety Board Certified Behavior Analysts (BCBAs) and 19 editorial board members evaluated hypothetical data presented in a multielement design. We manipulated the variability, trend, and mean shift of the data and asked the participants to determine if the data demonstrated experimental control. The results showed that variability, trend, and mean shift interacted to affect the participants' ratings of experimental control. The level of agreement between participants was variable, but was generally lower than in previous research.

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Many studies have shown that pigeons will sometimes behave suboptimally by choosing an option that provides food less frequently over one that provides food more frequently. The critical factor in driving suboptimal behavior in these procedures is that the delayed outcomes are differentially signaled on the suboptimal alternative, but not the optimal alternative. Although this procedure is frequently cited as potentially analogous to human gambling, there is little empirical data to evaluate this assertion. The present study tested both pigeon (Experiment 1) and human (Experiment 2) subjects with a suboptimal choice task. Subjects chose between a suboptimal alternative that provided a large reinforcer 20% of the time and an optimal alternative that always provided a small reinforcer. Stimuli presented during the delays signaled the outcomes on the suboptimal alternative in some conditions. When outcomes were signaled, pigeons chose the suboptimal alternative more frequently than did humans. When the outcomes were not signaled, pigeons' choices became more optimal, but humans' choices did not. Humans' suboptimal choice was unrelated to performance on a probability discounting task. Overall, these findings suggest that although both pigeons and humans can choose suboptimally, more research is needed in order to determine whether non-human performance on this task can serve as a model for human gambling.