by Patrick Appel

Jonah Lehrer explains what's going on inside your mind when watching a dirty movie:

Why do humans (especially men) get so excited by seeing someone else have sex? At first glance, the answer seems obvious: watching porn triggers an idea (we start thinking about sex), which then triggers a change in our behavior (we become sexually aroused). This is how most of us think about thinking: sensations cause thoughts which cause physical responses. Porn is a quintessential example of how such a thought process might work.

But this straightforward answer is probably wrong. Porn does not cause us to think about sex. Rather, porn causes to think we are having sex. From the perspective of the brain, the act of arousal is not preceded by a separate idea, which we absorb via the television or computer screen. The act itself is the idea. In other words, porn works by convincing us that we are not watching porn. We think we are inside the screen, doing the deed.

Mirror neurons facilitate this process by allowing the brain to automatically imitate the actions of somebody else. So if I see you smile, or lick an ice cream cone, or do something X-rated, then my mirror neurons light up as if I were smiling, or licking an ice cream cone, or doing something X-rated. We mirror each others movements, which allows us to make sense of all these flailing limbs and contorted muscles; the body is a pretty tough thing to read.

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