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The optimism bias (also known as unrealistic or comparative optimism) is a cognitive bias that causes a person to believe that they are less at risk of experiencing a negative event compared to others. There are four factors that cause a person to be optimistically biased: their desired end state, their cognitive mechanisms, the information they have about themselves versus others, and overall mood. The optimistic bias is seen in a number of situations. For example: people believing that they are less at risk of being a crime victim, smokers believing that they are less likely to contract lung cancer or disease than other smokers, first-time bungee jumpers believing that they are less at risk of an injury than other jumpers, or traders who think they are less exposed to losses in the markets.〔Elder; Alexander "Trading for a Living; Psychology, Trading Tactics, Money Management" John Wiley & Sons 1993, Intro – sections "Psychology is the Key" & "The Odds are against You", And Part I "Individual Psychology", Section 5 "Fantasy versus Reality" ISBN 0-471-59224-2〕 Although the optimism bias occurs for both positive events, such as believing oneself to be more financially successful than others, and negative events, such as being less likely to have a drinking problem, there is more research and evidence suggesting that the bias is stronger for negative events.〔 Different consequences result from these two types of events: positive events often lead to feelings of well being and self-esteem, while negative events lead to consequences involving more risk, such as engaging in risky behaviors and not taking precautionary measures for safety.〔 == Measuring == The optimistic bias is typically measured through two determinants of risk: absolute risk, where individuals are asked to estimate their likelihood of experiencing a negative event compared to their actual chance of experiencing a negative event (comparison against self), and comparative risk, where individuals are asked to estimate the likelihood of experiencing a negative event (their personal risk estimate) compared to others of the same age and sex (a target risk estimate).〔 Problems can occur when trying to measure absolute risk because it is extremely difficult to determine the actual risk statistic for a person.〔 Therefore, the optimistic bias is primarily measured in comparative risk forms, where people compare themselves against others, through direct and indirect comparisons.〔 Direct comparisons ask whether an individual's own risk of experiencing an event is negative, positive or equal than someone else's risk, while indirect comparisons ask individuals to provide separate estimates of their own risk of experiencing an event and other's risk of experiencing the same event.〔 After obtaining scores, researchers are able to use the information to determine if there is a difference in the average risk estimate of the individual compared to the average risk estimate of their peers. Generally in negative events, the mean risk of an individual appears lower than the risk estimate of others.〔 This is then used to demonstrate the bias' effect. The optimistic bias can only be defined at a group level, because at an individual level the positive assessment could be true.〔 Likewise, difficulties can arise in measurement procedures, as it is difficult to determine when someone is being optimistic, realistic, or pessimistic.〔〔 Research suggests that the bias comes from an overestimate of group risks rather than underestimating one's own risk.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Optimism bias」の詳細全文を読む スポンサード リンク
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