Intact capacity for implicit learning in obsessive-compulsive disorder.

Background And Objectives: Individuals with OCD tend to rely on explicit processing when performing implicit learning tasks. However, it is unclear whether this tendency reflects impaired capacity for implicit processing or a preference toward explicit processing. We sought to use a psychometrically valid task to examine the hypothesis that individuals with OCD have intact capacity for implicit learning.

Methods: Twenty-four participants with OCD and 24 non-psychiatric controls completed a modified artificial grammar learning task where acquisition and retrieval of the underlying grammatical rules are considered strictly implicit. In an exploratory condition designed to examine the effect of nudging participants toward controlled processing, 12 participants in each group were told that the stimuli presented at acquisition were composed according to grammatical rules and were encouraged to identify these rules.

Results: As predicted, participants with OCD acquired and expressed knowledge of the grammatical rule, demonstrating intact capacity for implicit learning, with no differences found between the OCD and controls on the extent of implicit learning. The exploratory intentional learning instructions had no effect, as participants in this condition were unable to adhere to the instructions, supporting the robust implicit nature of the artificial grammar learning task.

Limitations: The relatively small sample size did not allow comparisons between OCD symptom subtypes.

Conclusions: Our results provide evidence for intact implicit learning in OCD, and challenge previous studies suggesting a general deficiency in implicit learning in OCD.