The Magical Spread of Contamination

One of the most common themes in obsessive-compulsive disorder is the fear of contamination. If it were just a matter of thinking one particular thing is contaminated, then perhaps the OCD sufferer would be able to do without that particular thing and life would move on. This could perhaps be expensive, but feasible.
Unfortunately, it isn’t so easy. As everyone familiar with OCD knows, contaminated objects do not keep their contamination to themselves; they spread it, in a variety of ways.
The “contaminated” label that the brain applies to different objects has its origin in the amygdala, the part of the lower cortex that identifies threats in the environment, internal or external. With contamination fears, an object is labeled a threat; then, anything that that object comes in contact with gets joined with it, sharing in the threat-label.
If you look closely at the process, you can see that this is the lower cortex at work — it doesn’t have access to higher-level reasoning, and instead operates on a “magical” level. So if a person considers cockroaches to be sources of contamination, then they wouldn’t be surprised that they also find things that a roach was seen touching as also being contaminated. In some ways, this is reasonable, and so this could be the work of the higher cortex. Nothing unusual here so far.
But if the person has roach-contamination OCD, the contamination can spread in more magical ways: for instance, if they were holding onto an object while they found a roach in the house, than that object can be contaminated, even without coming in contact. (Some people feel that even their eyes are contaminated by seeing contaminated objects, and have a compulsion to wash them after seeing something ‘bad.”) Even thinking about a roach, while holding a neutral object, might contaminate that object for the OCD sufferer.
So there are two ways our minds can process the spreading of contamination from one object to another: a higher cortical, more reasonable way, which generally obeys known laws of physics and logic; and a lower cortical, magical way that operates independent of any laws. The latter is what dominates in OCD.
Going back to the roach example, if a roach were to touch an object, like a shoe, the higher cortical path would involve these generalizations: first, the shoe would not be equally contaminated as the roach; second, the shoe’s contamination would tend to wear off over time; third, the shoe would still be considered safe, even without cleaning it; and fourth, the shoe wouldn’t be able to contaminate further objects.
In OCD, however, the roach-touched shoe would be as contaminated as the roach itself, or close to it; the contamination would likely last for years, or indefinitely; the whole shoe would be considered unsafe, even on the inside; and the shoe would contaminate other objects it touched. All of this points to what I have been calling the “magical” spread of contamination — it is as if the contamination is a spell cast on objects, easily transferred to others, of great danger and endless duration.
This magical way of spreading contamination forms the basis of an approach to exposure therapy, called the “pan-exposure.” Please see this post for details.