Surprise Definition

Surprise is the sense of astonishment, wonder, or amazement that is caused by something sudden or unexpected. The experience of surprise varies with the importance of the outcome, as well as beliefs about the outcome. Some formalists have offered mathematical definitions of surprise (i.e., a comparison of Bayesian priors and posteriors), but there is little consensus about a psychological definition. Some researchers treat surprise as a cognitive assessment based on the probability of an event, whereas others treat it as an emotion, on par with happiness, sadness, anger, disgust, and fear because of its unique pattern of facial expressioSurprisens. If surprise is an emotion, it is an unusual one; it can be positive or negative, and it dramatically shapes the experience of other emotions.

Importance of Surprise

The concept of surprise is relevant to many aspects of human behavior. Humans notice and focus on surprising events and are more likely to attend to surprising events. Surprise facilitates curiosity and learning. It also affects beliefs about other events. When a person takes an unexpected stance that violates his or her self-interest, the person’s arguments are surprising and quite often more persuasive.

Surprise is a key factor in emotional life. Neurological studies show that when monkeys expect a reward, dopamine neurons fire. When monkeys get the reward, neuronal firing depends on prior expectations. Unexpected rewards lead to greater firing than expected rewards. Apparently, unexpected pleasures are more rewarding than expected ones.

What Makes Something Unexpected?

If surprise depends on sudden or unexpected events, what makes something unexpected? An unexpected event is a low-probability event. Surprise usually follows the event, but it can also be anticipated. However, the intensity and duration of surprise may be harder to forecast than the valence of a future event.

An unexpected event may be an unfamiliar event. A tourist who travels to Hawaii may be surprised to see 30-foot waves, despite the fact that such waves are common during the winter months and familiar to local inhabitants. An unexpected event may also be a novel event. Most people expect swans to be white, so a black swan is unique and rare.

Unexpectedness depends on the ease with which a person can imagine an event. Some people are more surprised to draw a red ball at random from an urn containing 20 balls, 1 of which is red, than to draw a red ball from an urn with 200 balls, 10 of which are red. Although the two events are equally likely, the first event can happen in only one way, whereas the second event can happen in 10 different ways.

Unexpectedness also varies with the ability to imagine other events unfolding. Some people are more surprised to select a red ball at random from a jar with 1 red ball and 19 blue balls than to pick a red ball from a jar with 20 balls, each a different color. In the first case, the blue ball is the only referent, but in the second, there are many referents. In a similar fashion, a negative event is often more surprising, and more tragic, if there were many ways it could have been avoided than if there was only one way.

Finally, unexpectedness depends on social and cultural norms. A person learns how to react to events from his or her social environment. Research shows that East Asians tend to take contradictions and inconsistencies for granted and are less surprised by most events than are Americans.

Magnifier of Emotions

Psychologists have developed a theory that connects surprise to the pleasure or pain of an outcome. Decision affect theory predicts that surprising outcomes have greater emotional intensity than expected outcomes; a surprising positive event is more pleasurable than an expected positive event, and a surprising negative event is more painful than an expected negative event.

In gambling studies, a surprising outcome had a small probability of occurrence. Surprising wins or losses are more intense than expected wins or losses. In studies of skill, a surprising outcome is one that deviates from expectations. A person may expect to succeed or fail at a task. In this case, surprising success is more pleasurable than expected success, and surprising failure is more painful than expected failure.

When assessing the ability to be successful, a person often sees himself or herself through rose-colored glasses. Inaccurate self-assessments are sometimes called positive illusions. One such illusion is overconfidence, the tendency of a person to believe he or she will do better at a task of skill than reality suggests. Overconfidence has two detrimental effects on affective experiences. It makes successes less surprising and therefore less pleasurable, and it makes failures more surprising and therefore more painful.

Another positive illusion is called hindsight. After learning what happened, a person thinks he or she knew it all along. The person recollects past beliefs as too accurate. Hindsight makes events seem less surprising, and it has one detrimental effect on emotional experiences. An expected negative event will be less painful than a surprising negative event, but an expected positive event will be less pleasurable than a surprising positive event.

Strategic Shifts

Can beliefs be systematically altered before an event occurs to make a person feel better? People are aware that bad news feels worse when unexpected, and some lower their expectations to avoid a surprising disappointment. In one experiment, researchers asked college sophomores, juniors, and seniors to estimate their starting salary for their first job at the beginning and end of the spring term. Sophomores and juniors showed no change, but seniors lowered their estimates. They were the only group that would soon face reality.

People also shift their beliefs after the event, especially if it was bad. They convince themselves that the event was inevitable. For example, sports fans might convince themselves that their team lost because the umpire was biased. Such thoughts diminish the pain by making the loss seem expected. To feel better about negative events, people should remember that much of life is unpredictable, and surprises should be expected.


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  2. Mellers, B. A., & McGraw, A. P. (2004). Self-serving beliefs and the pleasure of outcomes. In J. Carrillo & I. Brocas (Eds.), The psychology of economic decisions. Vol. 2: Reasons and choices (pp. 31-48). New York: Oxford University Press.