Compulsivity is associated with accelerated stimulus- response habit learning

A prominent theory suggests that clinically significant compulsive behaviours arisefrom an overexpression of the brain’s habit system. However, most evidence for thiscomes indirectly – observing reduced goal directed or ‘model-based’ control incompulsive individuals. In a pre-registered study, we directly examined stimulus-response habit learning in compulsivity. We trained N = 1000 participants for 7 dayson a smartphone-based habit-learning task, confirming that habits became morepronounced following extended training (6- vs 1-day) and under time pressure.Crucially, habit expression was associated with higher levels of compulsivity, but notanxious-depression or a range of other clinically relevant repetitive behaviours (i.e.,tics, skin-picking, hair pulling). These findings add an important new dimension to thehabit hypothesis of compulsivity, suggesting enhanced habit formation may also playa key role in its overexpression.