Ageism American society has been described as maintaining a stereotypic and often negative perception of older adults. This negative and/or stereotypic perception of aging and aged individuals is readily apparent in such areas as language, media, and humor. For example, such commonly used phrases as 'over the hill' and 'don't be an old fuddy-duddy' denote old age as a period of impotency and incompetency. The term used to describe this stereotypic and often negative bias against older adults is ageism. Ageism can be defined as 'any action, or institutional structure which subordinates a person or group because of age or any assignment of roles in society purely on the basis of age'. As an 'ism', ageism reflects a prejudice in society against older adults. Ageism, however, is different from other 'isms' (sexism, racism etc.), for primarily two reasons. First, age classification is not static. An individual's age classification changes as one progresses through the life cycle. Thus, age classification is characterized by continual change, while the other classification systems traditionally used by society such as race and gender remain constant. Second, no one is exempt from at some point achieving the stares of old, and therefore, unless they die at an early age, experiencing ageism. The later is an important distinction as ageism can thus affect the individual on two levels. First, the individual may be ageist with respect to others. That is s/he may stereotype other people on the basis of age. Second, the individual may be ageist with respect to self. Thus, ageist attitudes may affect the self concept. Much research has been conducted concerning ageism. However, the empirical evidence is inconclusive. Some research demonstrates the existence of ageist attitudes and other research does not. This discrepancy is most likely the result of methodological differences and, in particular, methodological errors. A brief discussion of the major methodological errors or problems found in ageism research may be helpful in clarifying this point. What is the exact meaning of ageism, according to the passage?