Reinforcer devaluation affect within-bout responses to a greater degree than bout-initiation responses on human free-operant responding.

Six experiments with human participants explored the effects of a reinforcer devaluation procedure on the microstructure of free-operant schedule performance, which is theoretically and empirically novel. The goal was to test whether different aspects of the microstructure of free-operant responding would be differentially affected by the manipulation to test the view that bout-initiation responses can be regarded as stimulus-driven habits both susceptible to devaluation, and within-bout responses as goal-directed actions that are susceptible to such effects. Humans responded to a fictitious investment game in which responses made investments in two countries with different currencies. These currencies had an exchange rate into Great British Pound (GBP), which could be manipulated to devalue the currency (reinforcer). In Experiments 1a and 2, random ratio schedules showed overall devaluation effects, which were limited to within-bout rates and more pronounced on longer ratios. In Experiments 1b and 3, random interval schedules showed limited devaluation effects, overall, except for with shorter intervals. This effect was seen on some schedules for within-bout responding. Experiments 4 and 5 manipulated the response-reinforcer feedback function (Experiment 4) and participants' ability to experience contingency variations by pretraining to be variable or static in response rates (Experiment 5). Only when there was a stronger response-reinforcer relationship (Experiment 4), which could be experienced due to variable responding (Experiment 5), did the devaluation effect occur, and these effects were limited to within-bout responses. These data suggest that an account of free-operant responding based on there being, at least, two classes of response-bout initiations that are stimulus-driven habits, and within-bout responses that are goal-directed actions-may explain many schedule effects. (PsycInfo Database Record (c) 2026 APA, all rights reserved).