Delay Discounting of Monetary and Social Media Rewards: Magnitude and Trait Effects

Methamphetamine increases risky choice in rats, but only when magnitude and probability of reinforcement are manipulated within a session

Risky choice is associated with maladaptive behaviors, particularly substance use disorders. Current animal models of risky choice are often confounded by other constructs like behavioral flexibility and suboptimal choice. The purpose of the current experiment was to determine if the psychostimulant methamphetamine, a drug whose popularity has increased in recent years, increases risky choice in an equivalent expected value (EEV) task. In the EEV task, rats are given a choice between two reinforcer alternatives that differ in magnitude and probability of delivery, but have equivalent expected value. Forty-eight Sprague Dawley rats were tested in three versions of the EEV task. In the first version of the EEV task, both reinforcer magnitude and probability were adjusted across blocks of trials for both alternatives. In the second and the third versions of the EEV task, reinforcer magnitude was held constant across each block of trials (either 1 vs. 2 pellets or 4 vs. 5 pellets). We found that male rats preferred the "riskier" option, except when reinforcer magnitudes were held constant at 4 and 5 pellets across each block of trials. Methamphetamine (0.5 mg/kg) increased preference for the risky option in both males and females, but only when both reinforcer magnitude and probability were manipulated across blocks of trials for each alternative. The current results demonstrate that both magnitude of reinforcement and probability of reinforcement interact to influence risky choice. Overall, this study provides additional support for using reinforcers with expected value to measure risky choice.

Problematic mobile phone use as impulsive choice: Development and empirical verification of a reinforcer-pathology model

Problematic mobile phone use is characterized by its "impulsive" nature; users engage in it despite their negative attitude toward it. From a behavioral-economic perspective, this attitude-behavior discrepancy is generated by competing contingencies that involve smaller-sooner social reinforcers associated with mobile phone use and larger-later prosocial reinforcers potentially compromised by phone use. Based on this conceptualization, the reinforcer-pathology model of problematic mobile phone use is proposed, which posits that such phone use stems from excessive delay discounting of the social and prosocial reinforcers and/or excessive demand for the social reinforcers. A secondary data analysis of previously published studies was conducted, with the novel addition of principal component analysis and hierarchical cluster analysis of these data. The results generated evidence that supports the reinforcer-pathology model proposed in this article. Based on the theoretical analyses and accumulated empirical evidence, theory-driven prevention and intervention strategies for problematic mobile phone use are proposed. Overall, the reinforcer-pathology model of problematic mobile phone use provides a comprehensive framework for understanding and addressing this growing issue.