Uncovering the Motor Dynamics of Obsessive-Compulsive Rituals Through Cluster Analysis.

Abstract: Rituals represent a prominent human behavior in different contexts such as daily routines, life cycle stages, and psychopathology, for example, obsessive compulsive disorder (OCD) where they are referred to as compulsions. OCD compulsions differ from habitual behaviors and stereotypies regarding their formal features: acts repetition, the addition of nonfunctional acts, and attentional focus on basic motor units. This study aims to categorize OCD compulsions based on the motor patterns of acts repetition and inclusion of nonfunctional acts. We analyzed 28 video-recorded OCD compulsions; we adopted a cluster analytic model to identify distinct patterns within the data and determine cluster characteristics. Our findings revealed a moderate negative covariance between nonfunctionality and repetitiveness, indicating that as nonfunctionality increased, repetitiveness decreased. Three distinct clusters in OCD rituals were identified according to the motor pattern: "idiosyncratic rituals," characterized by strong incorporation of nonfunctional acts; "iterative rituals" showing high repetitiveness; and "routines," with minimal repetition and limited inclusion of nonfunctional acts. These motor patterns highlight evolutionarily conserved behavioral strategies aimed at coping with conditions of environmental unpredictability. The findings might allow fine-grained discrimination of ritual compulsions and help target personalized interventions.