People’s tendency to overemphasize internal explanations for the behavior of others, while failing to take into account the power of the situation.

Example: While at the grocery store, you have an unpleasant encounter with a surly new cashier and go out of your way to tell your friends what a jerk he must be. The next time you see him, you bristle, but he’s incredibly pleasant. You conclude that he must have been having a bad day when you met him.