How We Know What Isn't So by Thomas Gilovich Read Free Book Online Page B

adolescence? Academic success? Happiness with chosen career? It is at times such as these, when the meaning of the phenomenon under investigation is unclear, that our preconceptions have their greatest effect. Any measure of personal adjustment that supports our initial beliefs is likely to be seized upon as the “true” test. In contrast, if someone were to claim that day care during infancy hinders subsequent “scholastic achievement,” there is less flexibility in how it should be defined (although some remains) and therefore less latitude for our preconceptions to exert an effect.
    An interesting analogue of the problem of multiple endpoints is what could be called the problem of “variable windows.” The essence of a number of beliefs is that certain events tend to happen within some (unspecified) period of time. The belief that things “happen in threes” is a perfect example: Many people believe that events like plane crashes, serial-killing sprees, or birth announcements tend to occur in triplets. It is almost certainly the case, however, that these beliefs are mere superstitions that stem from the tendency to allow the occurrence of the third event in the triplet to define the period of time that constitutes their “happening together.” If three plane crashes occur in a month, then the period of time that counts as their happening together is one month. If the third plane crash does not happen for another month, the relevant period of time is stretched to two months. By allowing the window of opportunity to be sufficiently flexible, such beliefs can only be confirmed.
MULTIPLE ENDPOINTS AND MULTI-FACETED EXPECTATIONS
     
    People often comment on the resemblance between a newborn baby and one or both of the parents. “He has his mother’s eyes.” “She sure has that Gilovich nose.” Interestingly, these same observations are often made when the child, unknown to the observer, has been adopted. Even when there is no genetic connection between parent and child, it is still possible to detect, from the vast number of possible features, a few striking similarities.
    This phenomenon illustrates a particularly common result of the problem of multiple endpoints that gives rise to a specific class of erroneous belief. Certain beliefs or suppositions imply a similarity between two entities: A child should look like his or her parents, identical twins should behave alike, or a personality description ought to resemble the person it describes. However, if the two entities are sufficiently complex, then mapping one onto the other will almost certainly produce a number of points of overlap, and the expectation will appear to be confirmed.
    One of the best examples of this phenomenon is the “Barnum effect,” named after circus entrepreneur P. T. Barnum because it was he who said “there’s a sucker born every minute.” The Barnum effect refers to the tendency for people to accept as uncannily descriptive of themselves the same generally worded assessment, as long as they believe it was written specifically for them on the basis of some “diagnostic” instrument such as a horoscope or personality inventory. Consider the following description:
    You have a strong need for other people to like you and for them to admire you. At times you are extroverted, affable, and sociable, while at other times you are introverted, wary, and reserved. You have a great deal of unused energy which you have not turned to your advantage. While you have some personality weaknesses, you are generally able to compensate for them. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations. You pride yourself on being an independent thinker and do not accept other opinions without satisfactory proof. You have a tendency to be critical of yourself. Some of your aspirations tend to be pretty unrealistic. 15
     

    If you see yourself in that description, you are not alone. Many