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| On the Behavioral Economics of Reinforcer Delays |
| Saturday, May 25, 2019 |
| 12:00 PM–12:50 PM |
| Swissôtel, Concourse Level, Zurich E-G |
| Area: EAB/BPN; Domain: Basic Research |
| Chair: David P. Jarmolowicz (The University of Kansas) |
| Abstract: Decades of behavioral economic research has clearly converged on a simple truth: Delay of reinforcement impacts choice. This consistent relation is important because individuals suffering from impulse control disorders such as drug addiction, problem gambling, and obesity consistently show response patterns such that delays of reinforcement disproportionately impact their choice. As such research efforts have begun to shift towards mitigating the effect of delays on individuals choices. Despite considerable efforts, however, our understanding of the mechanisms driving these choices remains incomplete. Improving our understanding of these mechanisms may facilitate future efforts to lessen the impact of delays on individuals' choice. The present symposium includes three talks focused on mechanisms by which delays of reinforcement may impact choice. Specifically, talks will be presented on 1) unit price modifications which accommodate patterns of rats' response allocation (i.e., switching) between alternatives in dynamic environment , 2) an examination of effects of delay exposure training on the rats' propensity to escape the experimental situation (i.e., delay aversion), and 3) effects of delay exposure training on animal models of attention deficit hyperactivity disorders' tolerance for increasing delays and dopamine function |
| Instruction Level: Intermediate |
| Keyword(s): aversion, behavioral economics, delay, neuroscience |
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| Signaled Delays, Unsignaled Delays, and Unit Price |
| ROBERT SCOTT LECOMTE (The University of Kansas), David P. Jarmolowicz (The University of Kansas) |
| Abstract: Individuals tend to allocate responding based on the costs and benefits of obtaining a reinforcer. Unit price effectively summarizes this cost to benefit ratio. Typically, unit price equations involve the fixed ratio (cost) over the unit of reinforcement (benefit). However, evidence suggests that delay to reinforcement can significantly impact the value of rewards. Taking this into account, the current study examines the effects of signaled delays versus unsignaled delays on unit price.
Female Long Evans rats responded on a concurrent progressive ratio (PR) progressive delay (PD) schedule in operant chambers. Completing ratios on the PD lever in the first phase of the study resulted in a signaled delay. Rats then responded on the same concurrent schedules in an unsignaled delay condition.
Within-session response allocation was analyzed via a unit price calculation. Of note, the unit price model in this study incorporated the delays in effect during session and the rate of reinforcer devaluation into the more standard approach to unit price, which only accounts for costs (FR) over benefits (SR+). Overall, higher ratios on the PR lever were completed before switching to the PD lever in the unsignaled condition. |
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| Potential Mechanisms of Delay-Exposure Training |
| SARA PECK (USU), Jillian Rung (Utah State University), Jay Hinnenkamp (Utah State), Gregory Madden (Utah State University) |
| Abstract: Delay-exposure (DE) training consistently and robustly reduces impulsive choice in rats. The behavioral mechanisms behind this effect are poorly understood. One published study suggests the mechanism is unrelated to interval timing (Rung, Buhusi, & Madden, 2018). The present study evaluated if DE training works by mitigating aversion to delay-paired stimuli – those encountered when rats choose the larger-later reward. Fifty-seven rats were randomly assigned to 120 days of training with delayed reinforcement (DE), training with immediate reinforcement (IE), or to a fallow Control group. As in prior experiments, DE rats had higher area under the curve (AUC) values, indicating fewer impulsive choices than IE or Control rats (see left panel of attached figure). Subsequently, all rats were given the opportunity to press a lever to temporarily escape from stimuli correlated with long or short time intervals to food. When these escape opportunities occurred in the impulsive-choice task, DE rats escaped from the delay-signaling stimulus less than IE and Control rats (see right panel of attached figure). When escape opportunities occurred outside the impulsive-choice task, the difference only approached significance. These results suggest DE training works, in part, by decreasing aversion to delay-signaling stimuli. |
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| Behavioral and Neurochemical Effects of Delay Exposure Training in Animal Models of Attention Deficit Hyperactive Disorder |
| TADD DAVID SCHNEIDER (University of Kansas), David P. Jarmolowicz (The University of Kansas) |
| Abstract: Attention Deficit Hyperactive Disorder (ADHD) is common among children aged 4-7, with nearly 1 million using pharmacological treatments. The current study used twenty-four experimentally naïve rats (sixteen Lewis, eight Fischer 344) divided into three groups: Lewis delay training, Lewis control, and Fischer control. Groups were either exposed to a delay training program (tandem FR1 DRO 17s) or a control condition. Following delay training, subjects were tested on a Progressive signaled delay procedure. After behavioral testing, animals were moved into neurochemical testing. Ex vivo brain slices procedures were used to evaluate effects on dopamine function in the striatum using titrating levels of amphetamines (typical medication for ADHD). Behavioral differences were seen across groups in both run rate and post-reinforcement pause. Neurochemical differences were seen across groups in the testing phase. This demonstrates that the building of delay histories not only impacts behavior but is correlated to functional differences in the reward processing region of the brain. These results will add to the literature and may provide an opportunity to look at the effects of non-pharmacological interventions in children diagnosed with ADHD. |
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