Our schemas help us organize the information we perceive about people, but we also have a need to explain why people say what they do or act in certain ways. The judgments that we make to explain behavior are known as attributions (Jones, 1990). Consider the following exchange:

Emma might attribute Caleb’s comment to his personality (“Caleb is obnoxious!”) or to the situation (“Wow, something has put Caleb in a bad mood”). When we attribute behavior to someone’s personality (or something within the person’s control), we call that an internal attribution. When we attribute it to the situation (or something outside the person’s control), that’s an external attribution. How do we decide? If Emma considers her experience with Caleb and remembers that he is not usually so blunt or harsh about other people, she will likely attribute his behavior to the situation, not his personality.

Unfortunately, we are not completely rational in how we make attributions. The fundamental attribution error is a bias we have that causes us to overemphasize internal causes and underestimate external causes of behaviors we observe in others (McLeod, Detenber, & Eveland, 2001; Ross & Nisbett, 1991). (For example, we might assume that “Mark failed the midterm because he was too lazy to study.”) The error works in the opposite way when we make attributions about ourselves. Owing to the self-serving bias, we usually attribute our own successes to internal factors (“I got an ‘A’ because I’m smart”) and attribute our failures to external effects (“I failed the midterm because my professor stinks”).