Prior research has shown that responding can be maintained under concurrent food and social reinforcement in rats, but little is known about interactions between these reinforcers. In the present study, we approached the problem from a behavioral-economic perspective, using demand-curve methods to analyze demand for, and interactions between, food and social rein-forcement. Four rats were given repeated choices between food and 10-s of social access to a partner rat on concurrent schedules, with social access arranged by lifting a door to a restraint, within which the partner rat was held. The fixed-ratio prices of the food and social interaction were varied, separately or together, generating within-subject demand functions. Demand for both food and social interaction decreased with increases in their own price (own-price elastic-ity), though food reinforcers were more robust (higher levels of consumption at the lowest price) and less sensitive to price (less elastic) than was social interaction. Demand for a constant-price of social interaction increased with increases in the price of food (positive cross-price elasticity), suggesting a substitutable relationship. Demand for a constant-price of food did not change with increases in the price of social access, suggesting no reinforcer interaction. Demand for food alone was less elastic than demand for food in the presence of social reinforcement opportunities, showing that value of food is modified by the presence and availability of social reinforcement. The results provide further evidence of the reinforcing value of social interaction, and how it is modified by the broader economic context in which it occurs, including the price and availability of qualitatively different reinforcers of higher value.
