Sympathetic magic in contamination-related OCD

We examined whether patients with contamination-related obsessive–compulsive disorder (OCD) are characterized by sympathetic magic beliefs (i.e., an irrational understanding of how contagion is transmitted). We asked OCD patients (OCs), non-anxious control participants (NACs), and anxious control participants (ACs) to identify a “contaminated” object and rate its degree of contamination on a 0–100 scale. Next, we touched a clean pencil to the object, and participants rated the degree to which the pencil was contaminated. A second pencil was touched to the first pencil and was then rated. This process was continued for 12 pencils (12 degrees of removal from the original object). The same process was repeated using threat-non-relevant stimuli. Results indicated that for threat-relevant stimuli, OCs seemed to perceive a “chain of contagion” in which successive degrees of removal from the original object were not rated as less contaminated. In contrast, NACs and ACs quickly identified the pencils as not contaminated, suggesting that they recognize the contamination as degrading across objects. This difference was not seen using threat-nonrelevant stimuli. We also found that ratings of looming vulnerability (a belief that the contamination is spreading, approaching, or escalating in threat value) mediated the relationship between diagnostic group and the chain of contagion. We suggest that this process may be consistent with the sympathetic magic and disease-avoidance models of disgust, and that disgust may be a fruitful area for exploration in the study of OCD.