In the case of uncertainty, expectation is what is considered the most likely to happen. Uncertainty is a term used in subtly different ways in a number of fields including Philosophy, Statistics, Economics, Finance, Insurance An expectation, which is a belief that is centred on the future, may or may not be realistic. Belief is the psychological state in which an individual holds a Proposition or Premise to be true The future is commonly understood to contain all events that have yet to occur A less advantageous result gives rise to the emotion of disappointment. An emotion is a mental and physiological state associated with a wide variety of feelings thoughts and behaviours Disappointment is the feeling of dissatisfaction that follows the failure of expectations to manifest If something happens that is not at all expected it is a surprise. An expectation about the behavior or performance of another person, expressed to that person, may have the nature of a strong request, or an order.

Particularly in social sciences including game theory, expectation plays one of the central roles. The social sciences comprise academic disciplines concerned with the study of the social life of human groups and individuals including Anthropology, Communication studies Game theory is a branch of Applied mathematics that is used in the Social sciences (most notably Economics) Biology, Engineering, In game theory, a Nash equilibrium constitutes a correct and stable set of expectations held by the players. In Game theory, the Nash equilibrium (named after John Forbes Nash, who proposed it is a Solution concept of a game involving two or more players in which Various other solution concepts of games such as rationalizability have been proposed according to how much knowledge players have on the expectation of other players' actions. In Game theory, rationalizability or rationalizable equilibria is a Solution concept which generalizes Nash equilibrium.

Emotion and Adaptation

In Emotion and Adaptation (Oxford University Press, 1991), Richard Lazarus asserts that people become accustomed to positive or negative life experiences which lead to favorable or unfavorable expectations with regard to present and near-future circumstances. Lazarus notes the widely accepted, philosophical principle that "happiness depends on the background psychological status of the person -- that is, the overall pattern of expectations and existential mood -- and cannot be well predicted without reference to" one's expectations [italics mine].

Also with regard to happiness or unhappiness, Lazarus notes that "people whose objective conditions of life are those of hardship and deprivation often make a positive assessment of their well-being," while "people who are objectively well off. . . often make a negative assessment of their well-being. " Lazarus argues that "the most sensible explanation of this apparent paradox is that people. . . develop favorable or unfavorable expectations" that guide such assessments.

See also

• Collective belief
• Culture-specific syndrome
• Delusion
• Folk psychology
• Gettier problem
• Nocebo
• Observer-expectancy effect
• Placebo
• Propositional attitude
• Propositional knowledge
• Self-deception
• Self-fulfilling prophecy
• Subject-expectancy effect
• Suggestibility
• Suggestion
• Syncopation
• Truth
• Thomas theorem
• Unintended consequence