Attribution theory is a Social Psychological theory that relates to the way in which people explain their own behavior and that of others. According to this theory, people tend to attribute (or explain) psychological or external causes as the determining factor in behavior. For example, if someone acts mean to you one day, would you attribute the behavior to the person being a jerk (internal attribution) or to the person having a bad day (external attribution)? Attribution theory examines the ways in which people make these attributions. Make sure you review the definition for the Fundamental Attribution Error, which relates directly to this.