This Month, Professor F.M. Moghaddam addresses the topic of 'intelligence in seniors'.Read this last of three articles.

"Well, I may be able to keep my money with me," said the elderly man sitting behind the computer, "but not my intelligence."

"Why not?" I asked.

"Oh, isn't it true that after twenty people start losing brain power?"

People hold many stereotypes about aging and intelligence, most of which are wrong. In the last two discussions I have focused on aging and memory, and in this discussion I want to put the spotlight on aging and intelligence. I shall point out that traditional stereotypes about how our mental abilities change as we age are often misguided.

Traditional psychology distinguishes between fluid intelligence , referring to basic mental abilities concerned with the perception of relationships, organization and remembering of information, drawing logical conclusions, and problem solving, and crystallized intelligence , intellectual performance heavily influenced by education, social experience and cultural practices. Intelligence tests are supposed to measure fluid intelligence independent of educational and cultural experience.

The Wechsler and the Stanford Binet continue to be the most widely used tests of intelligence.

The first modern IQ tests were designed for use in schools. Items were selected for inclusion in these tests to show a trend of more children getting the correct answer with increasing age. The general assumption was that at some age intelligence reaches a peak, and for this reason it becomes difficult to find items that a greater proportion of people get correct with increasing age. Ideas about the age at which intelligence "peaks" have been based in large part on cross-sectional studies, which involve comparing samples of people belonging to different age groups, including children, teenagers, young adults, and seniors. However, a major problem with cross-sectional studies is that we have to assume these samples are comparable in every way except age. This assumption is obviously wrong, because seniors who are, for example, 75 years old now were not like the teenagers of today when they were 16. Their nutritional, educational, and cultural conditions were very different, for a start. A much more effective approach is to conduct longitudinal studies, focusing on the same individuals over the course of their lives.

A consistent, if surprising, finding of longitudinal studies is that so-called "peak performance" on intelligence tests tends to be reached and sustained much later than had been expected. The Berkeley Growth Study followed the same individuals and found a peak in intelligence, not in the teens, but in the mid-twenties, with declines in only some areas starting in the mid-thirties. The Seattle Longitudinal Studies , perhaps the most rigorous research ever conducted on age and intelligence, led to even more intriguing and promising conclusions. While perceptual speed and numerical ability were shown to peak in the 20s, verbal ability and inductive reasoning did not decline among healthy individuals until in the 70s and 80s.

A number of smaller-scale longitudinal studies reveal the same trend, of intelligence peaking later than traditionally expected and also the peak being sustained longer. This trend of people maintaining or even exceeding peak performance in later years was confirmed by the famous Terman studies on gifted children , which began with the identification of 1000 gifted children between 1911-1924, and the subsequent tracking of their individual development.

The general conclusion one reaches from studies of aging and intelligence is that as long as good health is maintained , significant declines in most abilities do not take place until the 60s and 70s, and in the case of verbal abilities not until the 80s. Medical research is adding details to this picture. For example, a study reported in The Journal of the American Medical Association (July 7, 1999) confirmed that cognitive abilities do not decline with age for healthy individuals. This study involved the tracking of about 6,000 senior citizens over a decade and showed that for about seventy per cent of individuals evaluated there was no decline in cognitive abilities over the course of the study. However, individuals with particular health problems were eight times more likely to show a decline in cognitive functioning.

Thus, even using the traditional and narrow tests of abilities, healthy seniors have been shown to retain peak performance much longer than previously thought. Since the 1970s, to overcome some of the limitations of traditional measures of intelligence, researchers are focusing on wider conceptions of intelligence. These include emotional intelligence , how effectively individuals interpret, express, and regulate their own and others' emotions; practical intelligence , problem solving "common sense" strategies that are not formally taught but are based on tacit knowledge; and multiple intelligences , which includes linguistic, logical-mathematical, spatial, musical, bodily kinesthetic, interpersonal, intrapersonal, naturalistic, spiritual, and existential intelligences. On these types of intelligence, also, healthy seniors retain peak performance very well.

To sum up, as far as intelligence is concerned, as long as you remain healthy you can keep it with you.