Obsessive-Compulsive Tendencies and Action Sequence Complexity: An Information Theory Analysis

Obsessive-compulsive disorder (OCD) is a psychiatric condition that is primarily associated with anxiety provoking repetitive thoughts (i.e., obsessions) and actions that are manifested to neutralize the resultant anxiety (i.e., compulsions). Interestingly, OCD patients continue compulsive behaviors (e.g., repeatedly rechecking if the door is locked) although they are typically aware of the irrationality of these behaviors. This suggests that compulsive behaviors have habit-like features. We predicted that the motor actions (e.g., sequence of goalless key presses) would deviate from randomness in individuals with stronger obsessive-compulsive (OC) tendencies and thus expected to observe more rigid sequential action patterns in these individuals (e.g., pressing keys according to a motif). We applied entropy theory approach, defined as the rate of change of information in a given sequence, to test this hypothesis. We collected two different types of sequential behavioral data from healthy individuals and scored their obsessive-compulsive tendencies based on the Padua Inventory. In the first method, we asked participants to press one of the two buttons sequentially. In the second method, participants were asked to mark one of the four different options sequentially (on a multiple-choice optic form). The behavioral characterization was carried out by quantifying the entropy in the sequence of two sets of behavioral data using the Shannon metric entropy and Lempel-Ziv complexity measures. Our results revealed a negative relationship between the degree of washing tendencies and the level of information contained in action sequences. These results held only for the data collected with key presses and not for the choice sequences in the paper-pencil task. Based on these results, we conclude that the behavioral rigidity observed in the form of compulsive actions may generalize to some other behaviors of the individual.