Stimulant drugs have been shown either to increase or decrease rates of delay discounting (impulsive choice). These mixed findings may result from genetic, neurochemical, or environmental factors. Lewis (LEW) and Fischer 344 (F344) rats have neurochemical and behavioral differences that may be relevant to delay discounting and were used to examine effects of acute and chronic administration of d-amphetamine (d-AMP) on impulsive choice using a within-session delay-discounting procedure. Male LEW (n=8) and F344 (n=8) rats chose between one food pellet delivered immediately and three food pellets delivered after an increasing delay. Saline and d-AMP (0.1, 0.3, 1.0, and 1.7 mg/kg) were tested acutely and during chronic d-AMP exposure. Choice for the larger reinforcer decreased as the delay to its presentation increased for both strains at baseline. LEW rats made more impulsive choices than F344 rats as indicated by shorter indifference points, and this is consistent with previous research. Acute administration of d-AMP dose dependently increased larger-reinforcer choice and area under the curve (AUC) for LEW, but not F344 rats. During chronic exposure to d-AMP, larger-reinforcer choice and AUC increased relative to acute administration for F344 rats responding in shorter delay series, but not for F344 rats responding in longer delay series or for LEW rats. Differential effects of acute and chronic administration of d-AMP on impulsive choice in LEW and F344 rats may be a result of various factors, including genetic, neurochemical, and environmental variables. Future research should attempt to tease apart the relative contribution of each of these factors on impulsive choice.

Impulsive choice is correlated with behavioral problems such as attention-deficit/hyperactivity disorder and substance abuse. Effects of stimulant drug administration on impulsive choice are not consistent and may depend on baseline differences in impulsive choice. A within-session delay-discounting procedure in which choice was between one food pellet delivered immediately (impulsive choice) and three food pellets delivered after increasing delays (self-controlled choice) was used to determine effects of adding and subtracting delays common to both reinforcers on impulsive choice in male Sprague-Dawley rats (n=8). Delay discounting was observed and impulsive choice was quantified using area under the curve (AUC). Adding delays common to both reinforcers decreased impulsive choice and subtracting delays common to both reinforcers increased impulsive choice. Before administration of D-amphetamine (0.03-1.80 mg/kg, intraperitoneally), subjects were rank ordered into a low-AUC or a high-AUC group. Select doses of D-amphetamine decreased impulsive choice for subjects in the low-AUC group but not for subjects in the high-AUC group. These results indicate that impulsive choice can be altered by changing the delay common to both reinforcers and suggest that effects of D-amphetamine may depend, in part, on baseline differences in impulsive choice.

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Physical inactivity can contribute to serious chronic ill health effects such as heart disease, hypertension, obesity, type II diabetes, and even cancer (Centers for Disease Control and Prevention, 2017). Interventions designed to increase physical activity are needed to help address this socially significant issue. The current study was designed to replicate and extend past work to determine whether self-tailored deposit contracts could be used to increase physical activity (i.e., minutes exercised per week) at a gym for three sedentary adults using a changing-criterion design. Minutes exercised increased for all three participants, and participants met all of their goals across the 6-week intervention. In a follow-up, physical activity decreased but remained above that obtained during baseline. This research adds support to a growing body of literature showing that behaviorally based interventions such as self-tailored deposit contracts can be used to increase physical activity in gym settings with adults.

Differential-reinforcement-of-low rate (DRL) schedules are often used to reduce, not eliminate, behavior. We systematically replicated Austin and Bevan (2011) to determine whether the number of questions asked by two adults with intellectual disabilities working at adult-day-training centers could be reduced using a full-session DRL. The full-session DRL involved delivery of a reinforcer at the end of the day if the number of questions asked was less than a specified number during the entire session. Questions, up to a specified number, were also reinforced withinsession. The full-session DRL reduced the number of questions asked by both participants and increased duration of task engagement for one participant.