Acute stress induces habit formation as evidenced by a contingency degradation task

Instrumental behaviour is goal-directed when controlled by the value of the outcome and knowledge of the action-outcome contingency, otherwise it is deemed to be controlled by external stimuli (habit). It is accepted that stress modulates the control of instrumental actions in a manner that favours habitual over goal-directed control. Indeed, while existing research extensively links stress to habit formation, in humans this has primarily been based on manipulations of outcome value, which is tested in extinction. Yet, stress also produces resistance to extinction, so the role of stress on habit expression is unclear. Here, we used a contingency degradation task to examine the relationship between stress and action-outcome contingency sensitivity in humans. Stressed participants displayed similar contingency knowledge about the action-outcome associative structure but this explicit knowledge fails to translate into behavioural sensitivity to changes in contingency. These results are discussed in light of the implications these findings hold for advancing the comprehension of stress-driven behaviours – particularly within the context of psychiatric disorders.