The brain backfire effect

 If you look at a brain scan of people who are listening to a political argument that contradicts their own position, the blood in the part of the brain responsible for rational thought is depleted and is not replenished until the person hears a statement that confirms their position. When confronted with new ideas, your brain literally closes up shop and throws down the blinds until a friendly and well-known visitor knocks at the door.

In other words, our unconscious minds see our personal ideas as a great treasure, and competing ideas as would-be looters; when they’re detected by the unconscious’ security system, it unleashes the dogs and locks the gate.