Intelligence
Influences Upon Intellectual Development
Intellectual competence does not operate within a vacuum. It is affected both by an individual's physiological state (i.e., the individual's state of health and, in old age particularly, the presence or absence of chronic disease), as well as the presence or absence of a favorable environmental context and adequate support systems. Figure 4 provides a conceptual schema of the influences that impact the adult development of cognitive/intellectual competence.
Adult cognitive functioning must, of course, be initially based upon both heritable (genetic) influences and the early environmental influences typically experienced within the home of the biological parents. It has been suggested by some behavior geneticists that much of the early environmental influences are nonshared (i.e., not shared by all members of a family). However, there is retrospective evidence that some early shared environmental influences may affect adult intellectual performance (see Schaie & Zuo, 2000). Both genetic and early environmental factors are thought to influence midlife cognitive functioning. Early environmental influences will, of course, also exert influences on midlife social status. Genetic factors are also likely to be implicated in the rate of cognitive decline in adulthood. Thus far, the best-studied gene in this context is the apolipoprotein E (ApoE) gene, one of whose alleles is thought to be a risk factor for Alzheimer's disease. ApoE status is therefore also considered a factor in cognitive development (the expression of this gene is probably not important prior to midlife).
Influence of health. Considerable information is available on the reciprocal effects of chronic disease and intellectual abilities. It has been observed that decline in intellectual performance in old age is substantially accelerated by the presence of chronic diseases. Conditions such as cardiovascular disease, renal disease, osteoarthritis, and diabetes tend to interfere with lifestyles that are conducive to the maintenance of intellectual abilities, while they also have direct effects on brain functioning. One study found that individuals free of chronic disease perform intellectually at levels that are characteristic of those seven years younger who are suffering from such diseases. However, it has also been shown that the age of onset of chronic disease is later, and the disease severity is less, when it occurs in individuals functioning at high intellectual levels.
Influence of lifestyles. Many studies have related individual differences in socioeconomic circumstances (and resultant lifestyles) to the maintenance of high levels of intellectual functioning into old age. In particular, it has been shown that individuals who actively pursue intellectually stimulating activities seem to decline at lower rates than those who do not. Such pursuits may include travel, intensive reading programs, participation in clubs and organizations, and cultural and continuing-education activities. Conversely, those individuals whose opportunities for stimulating activities have been reduced due to the loss of a spouse or other factors restricting
Figure 4 Conceptual model of health and environmental factors influencing the adult development of intellectual/cognitive competence.
Influence of education. Both the maintenance of intellectually stimulating activities and the pursuit of healthful lifestyles appear to be dependent to a considerable extent on an individual's level of attained education. Over the course of the twentieth century, in the United States, there was an average increase in educational exposure amounting to approximately six years for men and five years for women. This societal shift may be largely responsible for many of the favorable cohort differences in intellectual abilities described in this article. Those advantaged educationally are also more likely to be engaged in intellectually stimulating work experiences. These, in turn, have been shown to have favorable effects on the maintenance of intellectual functions into old age. Finally, it should be noted that while there is eventual age-related decline in intelligence for both the educationally advantaged and disadvantaged, those who start at a high level are likely to retain sufficient intellectual competence to last throughout life.
K. WARNER SCHAIE
See also AGE-PERIOD-COHORT MODEL; CREATIVITY; FUNCTIONAL ABILITY; LEARNING; PROBLEM SOLVING, EVERYDAY; WISDOM.
BIBLIOGRAPHY
ARBUCKLE, T. Y.; MAAG, U.; PUSHKAR, D.; and CHAIKELSON, J. S. "Individual Differences in Trajectory of Intellectual Development over 45 Years of Adulthood." Psychology and Aging 13 (1998): 663–675.
BALTES, P. B. "The Aging Mind: Potentials and Limits." Gerontologist 33 (1993): 580–594.
BALTES, P. B.; MAYER, K. U.; HELMCHEN, H.; and STEINHAGEN-THIESSEN, E. "The Berlin Aging Study (BASE): Overview and Design." Ageing and Society 13 (1993): 483–533.
BINET, A., and SIMON, T. "Methodes Nouvelles pour le Diagnostic du Niveau Intellectuel des Anormaux." L'Annee Psychologique 11 (1905): 102–191.
BOSWORTH, H. B., and SCHAIE, K. W. "Survival Effects in Cognitive Function, Cognitive Style, and Sociodemographic Variables in the Seattle Longitudinal Study." Experimental Aging Research 25 (1999): 121–139.
BUSSE, E. W. "Duke Longitudinal Studies of Aging." Zeitschrift für Gerontologie 26 (1993): 123–128.
CARROLL, J. B. Human Cognitive Abilities: A Survey of Factor-Analytic Studies. New York: Cambridge University Press, 1993.
CUNNINGHAM, W. R., and OWENS, W. A., JR. "The Iowa State Study of the Adult Development of Intellectual Abilities." In Longitudinal Studies of Adult Psychological Development. Edited by K. W. Schaie. New York: Guilford, 1983. Pages 20–39.
EICHORN, D. H.; CLAUSEN, J. A.; HAAN, N.; HONZIK, M. P.; and MUSSEN, P. H. Present and Past in Middle Life. New York: Academic Press, 1981.
GRIBBIN, K.; SCHAIE, K. W.; and PARHAM, I. A. "Complexity of Life Style and Maintenance of Intellectual Abilities." Journal of Social Issues 36 (1980): 47–61.
GUILFORD, J. P. The Nature of Human Intelligence. New York: McGraw-Hill, 1967.
HORN, J. L., and HOFER, S. M. "Major Abilities and Development in the Adult Period." In Intellectual Development. Edited by R. J. Sternberg and C. A. Berg. Cambridge, U.K.: Cambridge University Press, 1992.
HULTSCH, D. F.; HERTZOG, C.; SMALL, B. J.; MCDONALD-MISZLAK, L.; and DIXON, R. A. "Short-Term Longitudinal Change in Cognitive Performance in Later Life." Psychology and Aging 7 (1992): 571–584.
MATARAZZO, J. D. Wechsler's Measurement and Appraisal of Adult Intelligence, 5th ed. Baltimore: Williams & Wilkins, 1972.
MCARDLE, J. J. "Structural Factor Analysis Experiments with Incomplete Data." Mutivariate Experimental Research 29 (1994): 404–454.
MCARDLE, J. J., and PRESCOTT, C. A. "Age-Based Construct Validation Using Structural Equation Modeling." Experimental Aging Research 18 (1992): 87–115.
PLOMIN, R., and DANIELS, D. "Why Are Two Children in the Same Family So Different from Each Other?" The Behavioral and Brain Sciences 10 (1987): 1–16.
POON, L. W.; SWEANEY, A. L.; CLAYTON, G. M.; and MERRIAM, S. B. "The Georgia Centenarian Study." International Journal of Aging and Human Development 34 (1992): 1–17.
ROTT, C. "Intelligenzentwicklung im Alter [Development of Intelligence in Old Age]." Zeitschrift für Gerontologie 23 (1990): 252–261.
SANDS, L. P.; TERRY, H.; and MEREDITH, W. "Change and Stability in Adult Intellectual Functioning Assessed by Wechsler Item Responses." Psychology and Aging 4 (1989): 79–87.
SCHAIE, K. W. "Midlife Influences upon Intellectual Functioning in Old Age." International Journal of Behavioral Development 7 (1984): 463–478.
SCHAIE, K. W. "The Hazards of Cognitive Aging." Gerontologist 29 (1989): 484–493.
SCHAIE, K. W. "The Course of Adult Intellectual Development." American Psychologist 49 (1994): 304–313.
SCHAIE, K. W. "Generational Differences." In Encyclopedia of Gerontology. Edited by J. E. Birren. San Diego, Calif.: Academic Press, 1996a. Pages 567–576.
SCHAIE, K. W. Intellectual Development in Adulthood: The Seattle Longitudinal Study. Cambridge, U.K.: Cambridge University Press, 1996b.
SCHAIE, K. W. "The Impact of Longitudinal Studies on Understanding Development from Young Adulthood to Old Age." International Journal of Behavioral Development (2000).
SCHAIE, K. W.; PLOMIN, R.; WILLIS, S. L.; GRUBER-BALDINI, A.; and DUTTA, R. "Natural Cohorts: Family Similarity in Adult Cognition." In Psychology and Aging: Nebraska Symposium on Motivation, 1991. Edited by T. Sonderegger. Lincoln: University of Nebraska Press, 1992.
SCHAIE, K. W., and WILLIS, S. L. "Theories of Everyday Competence." In Handbook of Theories of Aging. Edited by V. L. Bengtson and K. W. Schaie. New York: Springer, 1999. Pages 174–195.
SCHAIE, K. W., and WILLIS, S. L. "A Stage Theory Model of Adult Cognitive Development Revisited." In The Many Dimensions of Aging: Essays in Honor of M. Powell Lawton. Edited by B. Rubinstein, M. Moss, & M. Kleban. New York: Springer, 2000. Pages 175–193.
SCHAIE, K. W., and ZUO, Y. L. "Family Environments and Adult Cognitive Functioning." In Context of Intellectual Development. Edited by R. L. Sternberg and E. Grigorenko. Hillsdale, N.J.: Erlbaum, 2001.
SCHOOLER, C.; MULATU, M. S.; and OATES, G. "The Continuing Effects of Substantively Complex Work on the Intellectual Functioning of Older Workers." Psychology and Aging 14 (1999): 483–506.
SPEARMAN, C. "General Intelligence: Objectively Determined and Measured." American Journal of Psychology 15 (1904): 201–292.
STEEN, B., and DJURFELDT, H. "The Gerontological and Geriatric Population Studies in Gothenburg, Sweden." Zeitschrift für Gerontologie 26 (1993):163–169.
STERNBERG, R. J. Beyond IQ: A Triarchic Theory of Human Intelligence. Cambridge, U.K.: Cambridge University Press, 1985.
TERMAN, L. M. The Measurement of Intelligence. Boston: Houghton, 1916.
THORNDIKE, E. L., and WOODWORTH, R. S. "Influence of Improvement in One Mental Function upon the Efficiency of Other Mental Functions." Psychological Review 8 (1901): 247–261, 384–395, 553–564.
THURSTONE, L. L. Primary Mental Abilities. Chicago: University of Chicago Press, 1938.
WILLIS, S. L., and SCHAIE, K. W. "Everyday Cognition: Taxonomic and Methodological Considerations." In Mechanisms of Everyday Cognition. Edited by J. M. Puckett and H. W. Reese. Hillsdale, N.J.: Erlbaum, 1993.
WOODRUFF-PAK, D. S. "Aging and Intelligence: Changing Perspectives in the Twentieth Century." Journal of Aging Studies 3 (1989): 91–118.
YERKES, R. M. "Psychological Examining in the United States Army." Memoirs of the National Academy of Sciences 15 (1921): 1–890.
Additional topics
Medicine EncyclopediaAging Healthy - Part 2Intelligence - Historical Background, Conceptualizations Of Intelligence, Age Changes In Intelligence, Age Differences In Intelligence, Cohort Differences In Intellectual Abilities