Response rate correlates with indifference points in a delay‐discounting procedure

Abstract

To study how effort affects reward value, we replicated Fortes, Vasconcelos and Machado's (2015) study using an adjusting‐delay task. Nine pigeons chose between a standard alternative that gave access to 4 s of food, after a 10 s delay, and an adjusting‐delay alternative that gave access to 12 s of food after a delay that changed dynamically with the pigeons' choices, decreasing when they preferred the standard alternative, and increasing when they preferred the adjusting alternative. The delay value at which preference stabilized defined the indifference point, a measure of reward value. To manipulate effort across phases, we varied the response rate required during the delay of the standard alternative. Results showed that a) the indifference point increased in the higher‐response‐rate phases, suggesting that reward value decreased with effort, and b) in the higher‐response‐rate phases, response rate in the standard alternative was linearly related to the indifference point. We advance several conceptions of how effort may change perceived delay or amount and thereby affect reward value.

YEAB: YEAB Ease the Analysis of Behavior

“…Within this paper, we have detailed functions for data extraction from MED-PC output files, derivation of complex metrics related to interval timing using peak procedures, computation of the Kullback-Liebler divergence to identify changepoints, decomposition of the underlying processes governing inter-response times in classical schedules of reinforcement, and calculation of the area under the curve in delay discounting data (see Table 1). Shull & Grimes, 2003) Delay discounting models exp_fit(), hyperbolic_fit() (Bickel et al, 1999;García-Leal et al, 2019;Mazur & Biondi, 2009) Area under the curve for delay discounting data trapezoid_auc() (Myerson et al, 2001) Moreover, the package offers a diverse range of additional functions that enhance its flexibility and utility in various research scenarios. While we have not covered these features here due to space constraints, they are readily available for users to implement.…”