Originally published in United Academics Magazine on April 24, 2012.
Many of our cognitive abilities such as reasoning, memory and spatial visualization start to decline in our mid 20’s.Yet, it turns out that many older people are doing great. How can this be? I asked psychology professor Timothy Salthouse of the University of Virginia’s Cognitive Aging Lab, about the aging brain.
Studies by researchers like Timothy Salthouse have shown that our brain, like our body, peaks rather early in life. When people of different ages perform intelligence tests consisting of finishing sequences of numbers, solving visual puzzles, recalling lists of words and making block designs, generally the 25-year olds perform best and there is a steady decline in scores for older people. Interestingly, this does not necessarily prevent older people from being successful in the real world. (See for instance Brains and Business).
Salthouse suspects a number of mechanisms that could explain this. First of all, he argues that in daily life we seldom have to perform at our maximum level of functioning whereas this is what cognitive tests attempt to assess. Secondly, while cognitive ability (also called fluid intelligence) indeed starts to decrease after our 20’s, studies have also shown that accumulated knowledge, also called crystallized intelligence, increases until our 60’s. (See also Fluid versus Crystallized Intelligence). Obviously this could have a compensatory effect.
Brains and Business
While cognitive ability (indicated here by the top 25% scores on the reasoning part of the Wechsler Adult Intelligence Scale) starts to decline already in our 20’s, this will not hinder us becoming the CEO of a fortune 500 company 30 years later.
Furthermore, cognitive ability is clearly not the only determinant of successful functioning in life and it is possible that characteristics like motivation, effort, focus, flexibility, conscientiousness and social skills could play an important role. Finally, Salthouse suggests that older people might also adjust their actions to these changes. For instance, when people recognize a declining level of cognitive and sensory ability, they might avoid driving in rush hour and in the dark, shift jobs or rely more on others like co-workers and children.
Fluid versus Crystallized Intelligence
Although performance on an analytical reasoning test (fluid intelligence) declines through the years, performance on a crossword puzzle test (which relies much on accumulated knowledge or crystallized intelligence) increases.
People are getting older these days, but since we seem to cope pretty well with the decline of our mental capacity, is there any reason for concern?
“Although it is true that many of these changes may have relatively minor consequences, they could still be important as early signs of later pathologies such as dementia. Furthermore I suspect that most people would prefer to function at their peak throughout life, and it would be valuable to determine how that might be possible by identifying the causes of age-related cognitive decline.”
The popular media sometimes give the warning ‘use it or lose it’ in news on the aging brain. For instance, doing crossword puzzles would keep older people mentally sharp. I understand you are fairly skeptical of this idea. Can you explain?
“My skepticism concerns the existing evidence which is primarily based on interventions with few comparisons of effects on the rate of aging, and not the possibility that future research could reveal that the trajectory of cognitive aging might be modified by various lifestyle factors. At present, nearly all of the research is correlational, and a discovery that high functioning people are more likely to do crossword puzzles does not mean that it is the cause of their high functioning.”
What else could we do to prevent the decline of our cognitive ability when getting older? I understand recent studies suggest staying physically active might help?
“I suspect that anything that contributes to better physical health will likely also benefit cognitive health, and this certainly applies to physical exercise. However, it is very difficult to determine causes of cognitive change or decline because random assignment to lifestyle is not practical, and large numbers of individuals would probably have to be monitored for decades to assess effects on rates of cognitive change.”
What might be causing the decline in people’s cognitive abilities in the first place?
“In my opinion this is still one of the big questions in this field because there is not yet a consensus about the causes, and there is even debate about when age-related cognitive declines begin. I think it is noteworthy that various structural brain changes, such as regional volume, cortical thickness, etc. also exhibit similar age trends, but causal connections between the two types of age trends have not yet been made.”
From the beginning of your career you have focused on studying the effects of aging on cognition. What fascinated you about this subject?
“The field of aging and cognition has intrigued me because it is both challenging from a scientific perspective and important from the societal perspective. That is, there are few topics as complex as the human mind and the mechanisms of aging, and yet the potential benefits of optimizing the period of maximal functioning by compressing the period of morbidity, and possibly even eliminating some forms of dementia, would be enormous.”
You are 64 years old. Have you noticed any decline in your own cognitive ability?
“Yes, I have noticed certain declines, and particularly in some aspects of word finding. The primary consequences thus far have been brief periods of embarrassment, and I try to use them as motivations for working even harder to discover causes of cognitive aging.”
Salthouse, T. A. (2012). Consequences of age-related cognitive declines. Annual Review of Psychology, 63 (5), 201-226. DOI: 10.1146/annurev-psych-120710-100328
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