Goal-direction and habit in human and nonhuman behavioral sequences (behavior chains).

Habits are important in everyday life and are thought to be involved in several human behavioral pathologies, including addictions. Experiments with rats suggest that habit, as indexed by insensitivity of an instrumental response to separate devaluation of its outcome, develops with extended practice. Motivated behavior often involves a sequence or chain of behaviors (Rs), with each cued by a different discriminative stimulus (S). We therefore examined performance of a two-response discriminated heterogeneous behavior chain (R1-R2) in which R1 and R2 were occasioned by different Ss and were both required to earn a reinforcer. We further asked whether extended training decreases the sensitivity of R1 to the extinction of R2, which is known to decrease R1 and is analogous to an outcome devaluation effect. In Experiment 1 with rats, R1 was sensitive to extinction of R2 after moderate but not extended training, suggesting the development of habit. In Experiment 2, human participants learned three R1-R2 chains before one "R2" was extinguished. Extinction of R2 specifically decreased performance of the R1 that had been associated with it, but extended training did not reduce this effect. Based on findings in the nonhuman literature, Experiment 3 then had human participants learn only one R1-R2 chain before R2 was extinguished. Under these conditions, R1 became insensitive to extinction of R2 after extended training, consistent with the idea that habit can develop in a laboratory experiment with humans. The findings are discussed relative to difficulties demonstrating habits in humans. (PsycInfo Database Record (c) 2025 APA, all rights reserved).