Intelligence

Empirical work in geropsychology began in the early part of the twentieth century with the observation that there were apparent declines in intellectual performance when groups of young and old persons were compared on the same tasks. This early work was done primarily with measures designed for assessing children or young adults. The intellectual processes used in the development of cognitive structures and functions in childhood, however, are not always the most relevant processes for the maintenance of intelligence into old age, and a reorganization of cognitive structures (for example, mental abilities) may indeed be needed to meet the demands of later life. Nevertheless, certain basic concepts relevant to an understanding of intelligence in childhood remain relevant at adult levels. Changes in basic abilities and measures of intelligence must therefore be studied over much of the life course, even though the manner in which intellectual competence is organized and measured may change with advancing age.

This section will first review the historical background for the study of adult intelligence. Alternative formulations of the conceptual nature of intelligence will then be described. Next, changes in intellectual competence that represent actual decrement that individuals experience will be differentiated from the apparently lower performance of older persons that is not due to intellectual decline, but instead reflects a maintained, but obsolescent, functioning of older cohorts when compared to younger peers. This is the distinction between data on age differences gained from cross-sectional comparison of groups differing in age and data acquired by means of longitudinal studies of the same individuals over time. This discussion will also include information on the ages at which highest levels of intellectual competence are reached, magnitudes of within-generation age changes, and an assessment of generational differences. Some attention will be given to the distinction between academic and practical intelligence. Finally, the influences of health, lifestyles, and education will be considered. This will provide an understanding of why some individuals show intellectual decrement in early adulthood while others maintain or increase their level of functioning well into old age.

Intellectual development from young adulthood through old age has become an important topic because of the increase in average life span and the ever-larger number of persons who reach advanced ages. Assessment of intellectual competence in old age is often needed to provide information relevant to questions of retirement for cause (in the absence of mandatory retirement for reasons of age), or to determine whether sufficient competence remains for independent living, for medical decision making, as well as for the control and disposition of property. Level of intellectual competence may also need to be assessed in preparation for entering retraining activities required for late-life career changes.