Parallel goal-directed and habitual control of human drug-seeking: implications for dependence vulnerability

Dual-process theories of learning and addiction propose that whereas freely elected drug/reward-seeking is goal-directed in being mediated by the expected value of the outcome, cue-elicited drug/reward-seeking is habitual in being elicited directly by antecedent stimuli, without retrieving a representation of outcome value. To substantiate this claim, the current study conducted a human devaluation-transfer procedure in which young adult smokers were first trained on a concurrent choice task to earn tobacco and chocolate points before one outcome was devalued by specific satiety or health warnings against consumption of that outcome. When choice was again tested in extinction, the selective reduction in performance of the action associated with the devalued outcome indicated that choice was controlled by an expectation of outcome value, that is, was goal-directed. Moreover, the presentation of tobacco and chocolate cues enhanced selection of the response associated with that outcome, indicating that transfer was also mediated by the retrieval of the outcome representation. Paradoxically, however, the magnitude of this transfer effect was unaffected by devaluation, indicating that the stimulus retrieved a representation of outcome identity but not current incentive value. Individual differences in tobacco dependence in the young adult sample were associated with tobacco preference in the concurrent choice task but not with the devaluation or transfer effects. These data accord with dual-process theories in suggesting that drug/reward-seeking are mediated by goal-directed and habitual controllers under freely elected and cued conditions, respectively, and that initial uptake of drug use is associated with hyper-valuation of the drug as an outcome of goal-directed drug-seeking rather than with accelerated habit formation.