What is possible and what is worth: Higher levers afford more work and enhance the value of leisure.

Abstract

This study investigated how variations in the physical properties of an operant manipulandum (i.e., lever height), affect behavior under a progressive ratio (PR) schedule. Lever height was analyzed from two complementary frameworks: the ecological theory of affordances and the economic theory of utility maximization, specifically through the Modular Maximization Theory. Rats were exposed to 60 progressive ratio (PR) sessions in which lever height varied daily pseudorandomly between 1, 11, and 18 cm. Results showed that breakpoints, response rates, and parameter estimates of response capacity (w) were significantly lower at 1 cm than at 11 and 18 cm, suggesting reduced motor affordance at floor level. The parameter z, indexing the value of the reinforcer relative to leisure, was higher at 1 cm, indicating a lower cost of effort at that position. Breakpoints indicated no carryover effects from prior sessions and stabilized rapidly from the first session of each condition, suggesting that adaptation to the affordances of the lever may be a distinct process from adaptation to reinforcement contingencies. These findings extend previous work on lever affordances and support the notion that operant performance is shaped by the interaction between environmental affordances and economic trade-offs. The integration of ecological and economic perspectives provides an account of how animals allocate behavior under varying physical and motivational constraints.