Discussion
This study investigated whether patients with OCD use more checking behavior than healthy controls in general, and whether this is more distinct when only mild uncertainty is induced. Furthermore, to investigate the specificity of the hypothesized effect, an anxiety control group was included. In both target-present and target-absent trials, there were no differences in search time and number of fixations between anxiety and healthy controls, whereas patients with OCD checked somewhat longer and used more fixations than both control groups in target-present trials (medium effect size). Crucially, in target-absent trials, in which all groups experienced less certainty than in target-present trials, the differences between the groups were larger (with medium to large effect sizes). In these mildly uncertain situations, patients with OCD checked longer and used more fixations than both anxiety and healthy controls. In target-present trials, the difference in search time between patients with OCD and the combined control groups was 11%, but in target-absent trials this difference was 22%. Thus, the specific tendency of patients with OCD to use more general checking behavior is more distinct under conditions of (mild) uncertainty. Additionally, there were no differences in the number of errors made during the task. Thus, although patients with OCD engaged in more checking behavior than healthy and anxiety controls, this did not increase accuracy. Therefore, the nature of the performed checking mimicked the irrationality of compulsive checking; it was continued beyond the point where the goal of the act was reasonably reached and had no natural terminus (Rachman, 2002).
