SEPC2025

Habits are learned when we repeat a rewarded action numerous times and are activated even when they contradict current goals. Individual differences in the balance between goal-directed and habit processes have been linked to transdiagnostic impulsivity among other personality traits. Essentially, individual differences studies suggest a trait of habit formation and expression tendency that differs across individuals. The amount of training required to form an inflexible stimulus-response habit may vary across individuals, as well as the tendency to express it once it is learned. However, the temporal stability of individual differences in habit formation and expression has never been directly examined, leaving open the question of whether a stable ‘habit trait’ exists in healthy populations. In our pre registered study, we addressed this gap by testing 79 participants in a forced-response task using a test–retest design. Participants underwent three consecutive days of training (1,000 trials per day), followed by a test on the fourth day and a retest on the fifth. The assessments were separated by a day to minimize the extinction of the acquired habit, enabling us to test whether the stability of habit expression is minimally stable. At the individual level, habitual responding during the test significantly correlated with habitual responding during the retest, providing evidence for the temporal stability of individual differences in habit expression. At the group level, we detected the expression of habits in both tests, although we observed a significant reduction in habit responding between test and retest. We discuss potential interpretations of this result pattern and its implications for understanding the stability of habits.