of incompleteness. This subjective feeling could be the result of changes in the stimulus-response associations produced by the excessive repetitions involving the checking behavior. Thus, over the years, increased sensorimotor circuit activity involved in habit-formation may have played a role in the transition from goal-directed (in this case, repetitive behaviors performed to relieve specific fears/worries) to habitual behaviors (here, repetitive behaviors to relieve feelings of incompleteness). In support of this hypothesis, studies examining the content of compulsions have reported that patients rate some of their compulsions as highly habit-like, i.e. they are felt to be automatic behaviors that are performed largely without conscious awareness, they have a long history of repetition over the patient’s life, and they form part of the patient’s daily routines [24]. Moreover, longer duration of illness predicted higher habit-ratings, in line with the idea that habit-like compulsions develop slowly over time [24]. Similarly, content analyses have revealed that some patients initially perform compulsions to elicit a sense of relief and that even though their compulsive rituals lose the ability to provide relief over time, the patients continue to perform the behaviors [38]. Further support for this hypothesis comes from experimental studies, which report excessive habit formation
