Seemingly "habitual” responses can be caused by both habits and strategic action selection

After we have practiced a task extensively, we often struggle to adapt to changes in task requirements, committing frequent habitual “slips of action” where we revert to our originally learned actions. Habitual action selection of this kind is often attributed to an obligatory stimulus-response association which competes with goal-directed responses. An alternative interpretation, however, is that, when task requirements change, we adjust by strategically building on our existing learning. That is, we may first retrieve the action we originally practiced, then switch this to a different action if needed. This retrieve-then-switch strategy may simplify learning and reduce cognitive effort under the altered task, particularly if changes from the original task are minor. To dissociate these two potential mechanisms underlying apparent habitual behavior, we recruited two groups of participants to practice a novel visuomotor association. We assessed habitual responses either by switching the responses for two out of five cues (partial-remapping group), in which case a retrieve-then-replace strategy may be advantageous, or by completely permuting the responses for all five cues (full-remapping group), in which case there would be no benefit to using a retrieve-then-replace strategy. We observed clear habitual behavior in both groups, confirming that participants do form an obligatory habit through practice. We also observed, however, that habitual responses were exacerbated in the partial-remapping group, supporting the view that participants adopted a retrieve-then-switch strategy in this case. Our findings support existing views of habits, but also demonstrate that measures of habitual behavior can be confounded by participant strategies.