To free, or not to free: Social reinforcement effects in the social release paradigm with rats

Abstract

The present research measured social reinforcement in rats, using a social-release procedure in which lever presses permitted 10-s access to a familiar social partner. The work requirements for reinforcement increased systematically according to progressive-ratio (PR) schedules. Social and food reinforcement value were compared across blocks of sessions (Experiment 1) and concurrently within the same sessions (Experiment 2). To assess motivational effects, response and reinforcer rates for both reinforcer types were studied under food restriction, social restriction, and combined food and social restriction. Responding was maintained by both reinforcers, albeit at substantially higher levels for food than for social access. Responding for social access decreased to low levels under extinction conditions, demonstrating functional control by the social-reinforcement contingency. Sensitivity to social restriction was seen in some conditions in Experiment 2, in which social reinforcers were earned earlier in the session (at lower food prices) under social restriction than under the other deprivation conditions. Altogether, results are consistent with a social reinforcement conceptualization, and demonstrate an important role for social contact in social release behavior. The study demonstrates a promising set of methods for analyzing and quantifying social reinforcement.

Rats (Rattus norvegicus) find occupancy of a restraint tube rewarding

“…In that procedure, free rats that had learned to open the door to a restraint tube containing a trapped rat failed to extinguish responding when responding no longer provided access to the tube but did provide proximity to the trapped rat. This result can be explained in terms of sociality, but not the reinforcing properties of tube entry since tube entry was denied (also see Hiura et al, 2018).…”

“…Hachiga et al (2018) interpreted these results as consistent with Silberberg et al's (2014) sociality premise. Hiura et al (2018) expanded on the results shown by Silberberg et al (2014) by arranging multiple trials in a session, presenting phases of acquisition and extinction, and varying postsession social restriction. Unlike Silberberg et al, they were able to show that free-rat behavior can come under the functional control of release of a restrained rat.…”

“…A second finding from Hiura et al (2018) was that unrestrained rats would often return to and enter the restraint tube. This finding echoes similar outcomes seen in Silberberg et al (2014) and the supplementary films of Ben-Ami Bartal et al (2011).…”

Renewal of extinguished operant behavior following changes in social context

“…These findings suggest that social stimuli can function as contextual cues during extinction and a change in the extinction context characterized by social stimuli may produce renewal of operant responding. However, the above conclusion is based on the assertion that the presence of the second rat during extinction functioned as a contextual stimulus, but it is possible that the second rat may have served as a source of social reinforcement (Angermeier, 1960;Evans et al, 1994;Hiura, Tan, & Hackenberg, 2018). If the second rat served as a source of social reinforcement, then removal of this rat during test may have produced resurgence of responding rather than renewal.…”

“…If the presence of the social stimulus rat was a source of social reinforcement, then its removal in the test session may have produced resurgence of lever press responding instead of renewal. In fact, there is evidence that rats will respond for access to another rat (Calcagnetti & Schechter, 1992;Evans et al, 1994;Hiura et al, 2018;Humphreys & Einon, 1981), which suggests that social interaction can be used as a reinforcer. In addition, limited access to another rat through a screen may also be a source of social reinforcement (Angermeier, 1960;Peartree et al, 2012).…”