Overjustification Effect

Overjustification Effect is the tendency to emphasize salient situational factors, while ignoring personal factors, to explain one's own behavior. For example, suppose you woke up late today. Instead of thinking that it was your own fault (that is, you slept late) you'd say the alarm did not go off. Another example is when students get a less than ideal grade in an exam. Instead of thinking about their own personal causes (e.g., did not study thoroughly, did not understand the reading material, poor nutrition), they would emphasize situational factors (e.g., the test was too hard, the teacher was too strict, the room was too dark). In short, in explaining our own behaviors, we tend to ignore our own faults, and then blame the situation (or anything besides ourselves).

One classic study [Overjustification in a Token Economy (1976)] showed how the overjustification effect can undermine motivation. After removing the rewards, children who were previously rewarded to play math games stopped playing, but the children who were never rewarded continued to play. This is because the previously rewarded children overjustified their behavior (playing math games) according to an external factor (reward), and ignored a personal factor (enjoyment).

See also: Fundamental Attribution Error (how we tend to evaluate other people's behaviors as personal causes, while ignoring situational factors)