Abstract Social distance describes how close an individual feels to another, and it is related to altruism. However, it is typically measured on an ordinal scale, hindering its precision and comparison with other phenomena. Although the open‐field procedure effectively converts social distance to a ratio scale, some issues remain. In this study, we developed the drawing‐a‐line (DLM) method to solve them. We asked participants to identify people in Positions 1, 2, 20, 50, and 100 on their social distance list and to complete a social discounting task. Then, for each person, participants drew a line to represent how close they felt to that person and we calculated the lengths to obtain a social distance value on a ratio scale. Results show that the DLM produced minimal variability in raw social distance at lower positions, reduced the s value in the distance function, and maintained a good fit of the data to the hyperbolic social discounting model. We discuss the results in terms of the strengths of the DLM, the methodological and conceptual significance of the decrement of the s value, and the limitations of the new method.
The peak interval procedure, in which subjects learn to cluster their anticipatory responses around delays to biologically critical outcomes, provides benchmarks for interval timing models. These include (a) the bistable response regime demarcated by an abrupt increase (start times) and a decrease (stop times) in response rates around the target time in individual trials; (b) bell-curve-shaped average response curves that superpose on a relative time scale; (c) lower coefficient of variation of stop times than start times; and (d) specific correlational patterns between these parameters, their mean, and difference. This article presents a multilayer computational model that predicts these key markers of timing behavior in the peak interval procedure. The first layer constitutes the clock stage, comprising uncoupled diffusion processes approaching a single boundary. The first crossing of the threshold for each diffusion process is broadcast to the downstream motor layer. The motor layer integrates the broadcast signals with a leak term scaled by the drift rate to avoid saturation and reset of motor system activity. The model is extended to account for real-time temporal discrimination. This family of models departs from the single-clock approach to modeling and meets the core empirical benchmarks of timing behavior.
Interventions seeking to reduce impulsive choice in nonhuman animals (i.e., preference for smaller sooner over larger later rewards [SSR vs. LLR]) often require long training durations. However, prior studies illustrate how a brief course of Pavlovian training can reduce rodents' impulsive choice by attracting them to the LLR and by providing an appetitive Pavlovian conditioned stimulus (CS) contingent on LLR choices. In these studies, the comparison group completed unpaired (UN) training where the CS and US never co-occurred. The present study added a truly random control (TRC) group to evaluate whether UN training made the CS aversive, exaggerating the effect of Pavlovian training on self-control. Following Pavlovian (PAV), UN, or TRC training, a lever CS was inserted into the chamber during half the delay to the LLR. PAV rats were significantly more attracted to the lever during training and chose the LLR significantly more often than TRC or UN rats. Significant sex differences were detected, with self-control influencing the effects of Pavlovian training predominantly observed in male rats. Because sex differences in self-control outcomes were not observed in the only other study to examine the effects of presenting an appetitive CS after LLR choices, possible reasons for this interexperiment difference are discussed.
Renewal, reinstatement, and other forms of recovery of learned behavior after extinction have been interpreted in terms of the concept of context. Context is defined here as the field of stimuli that is interrelated with the behavior of an individual in the present. Two important classes of stimuli that comprise context are discriminative stimuli and motivating operations. Two experiments examined interactions between discriminative and motivational aspects of context in the renewal and reinstatement of operant behavior following extinction in mice. In Experiment 1, mice received all operant acquisition and extinction sessions under 24 hr of food deprivation. In Experiment 2, mice received half of acquisition and extinction sessions under 24 hr of deprivation and the other half under nondeprived conditions. In both experiments, mice were tested for renewal and reinstatement after extinction, one group under 24 hr of deprivation and the other nondeprived. Results showed that the extent to which recovery occurred depended on relations between motivating operations (a) during acquisition/extinction learning and (b) during tests for renewal and reinstatement. Translational implications for the study of recovery of behavior after extinction in nonlaboratory circumstances are discussed.
