The fundamental attribution error is the tendency people have to overemphasize personal characteristics and ignore situational factors in judging others’ behavior. Because of the fundamental attribution error, we tend to believe that others do bad things because they are bad people. We’re inclined to ignore situational factors that might have played a role.

For example, if someone cuts us off while driving, our first thought might be “What a jerk!” instead of considering the possibility that the driver is rushing someone to the airport. On the flip side, when we cut someone off in traffic, we tend to convince ourselves that we had to do so.  We focus on situational factors, like being late to a meeting, and ignore what our behavior might say about our own character.

For example, in one study when something bad happened to someone else, subjects blamed that person’s behavior or personality 65% of the time. But, when something bad happened to the subjects, they blamed themselves only 44% of the time, blaming the situation they were in much more often.

So, the fundamental attribution error explains why we often judge others harshly while letting ourselves off the hook at the same time by rationalizing our own unethical behavior.