| As they grow older, most people wonder
how increasing age will affect intelligence. Can people in middle age and beyond
expect to think as effectively and to solve problems as efficiently as they have
in the past? One of the difficulties in comparing the intellectual functioning of people at different ages is the problem of cohort((具有相同特征的)一群人) effects. Different age groups in the population have experienced different historical events (wars, exposure to television, and so on) as well as changes in the general standard of living. Different scores that people of varying ages achieve on intelligence tests could be partly due to changes in diet, housing, or health care or, even more likely, to the amount and quality of education. Since the beginning of this century, there has been a trend for more people to go to school and to remain in school longer. Because it eliminates these cohort effects, a longevous (长寿的) study may be the best way to look at age-related changes in intellectual functioning. One of the few longevous studies of intellectual functioning is the Seattle Longevous Study, conducted by K. Warner Schaie and his associates. The original subjects, who ranged in age from 18 to 67, have now been tested 4 times over a 21 year period. These results have given a reasonably good picture of longitudinal(纵向的) change in cognitive abilities. The data show that there are only trivial changes in the kinds of abilities measured by intelligence tests before the age of 60, and no reliable decrease can be shown in these abilities before age 74. Although there is some decrease in measured ability in the late 60s and the 70s, it is not until age 81 that the average person falls below the middle range of performance for young adults. The data from the Seattle Longevous Study also suggest that there are very great individual differences in intellectual change throughout adulthood. Between the ages of 74 and 81, less than half the subjects showed any significant change. One important factor is health, especially the presence or absence of coronary(冠状) heart disease. Another is a high socioeconomic status, which is related not only to higher initial levels of functioning but to the maintenance of a higher level throughout life. A flexible life style in middle age, probably associated with a flexible personality style, also tends to predict high performance in old age. While some of these variables may have substantial hereditary (遗传的) elements, changes in environment and education could also be important in maintaining a higher level of functioning for many individuals. |