Alcohol seeking by rats becomes habitual after prolonged training.

BACKGROUND This study examines the effect of the amount of training on alcohol seeking behavior in rats. Contemporary theories of instrumental learning suggest that habit learning processes are involved in the development of the compulsive drug seeking that characterizes addiction. METHOD Wistar rats were trained to perform an instrumental response for a solution of ethanol. In Experiment 1, the rats received 2 instrumental training sessions, whereas animals in Experiment 2 received 2, 8, or 16 sessions. An aversion was then conditioned to ethanol by pairing it with LiCl, and the performance in extinction was subsequently tested. RESULTS Instrumental responding showed variable sensitivity to outcome devaluation as a function of the length of training. After 2 and 8 training sessions, but not after 16 sessions, drug seeking was influenced by a change in the value of ethanol. CONCLUSIONS The results suggest that alcohol seeking is more flexible and goal-directed in early stages of training, but it becomes habitual and less governed by its consequences with more extended training.