When refer to “fluid” and “crystallized” intelligence of older adults we are still using 1950s constructs. Constructs that are antiquated, eugenic constructs. Rarely do we see such references for younger people. There is not one article reporting that younger people’s crystalized intelligence is immature. But somehow these construct explain older adults diminished capacity for intelligence. By looking deeper into the use of these indicators of intelligence shows a glaring ageist perspective.
The Cattell-Horn Theory of Fluid and Crystallized Intelligence has been a resilient theory in psychology for more than 50 years, especially when referring to older adults. First proposed by the British psychologist Raymond Bernard Cattell in 1941 and later much refined with his student John L. Horn in 1964, Cattell believed that intelligence was a genetic attribute. He held eugenicist views that race played a major part in determining our intelligence. In line with the time, he also saw aging as a period of loss and decline.
Although Cattell is also credited with developing an influential theory of personality--16 personality factor model of personality--and creating new methods for statistical analysis--multivariate analyses, and with Charles Spearman developed Factor Analysis--his lasting legacy has been the proposal that intelligence is a reflection of some 100 discrete abilities which can be categorized broadly into two different sets of abilities: Fluid and Crystalized intelligence. These abilities have quite different trajectories over the course of development from childhood through adulthood. While Crystallized intelligence continues to incremental improve, Fluid intelligence peaks at around 20 years of age and then declines slowly by age 65.
Table: Fluid and Crystalized Intelligence across the Lifespan
(from Baltes P B, Lindenberger U, Staudinger U M, 1998)
Fluid intelligence is one of the discrete factors of general intelligence, proposed to be an innate and inherent learning capacity of all individuals. Fluid intelligence is independent of one’s education, learning and experience and reflects an individual’s natural mental ability. This is your “smarts.” Such capacity also includes your capacity for learning, problem solving and pattern recognition. Fluid intelligence is thinking on your feet…this is what Piaget refers to as “Intelligence is what you use when you don't know what to do.”
Crystallized intelligence on the other hand is the more stable memory-based intelligence. It is the accumulation of expertise through learning and skill development. It can be manipulated, mimicked. These are things that you ‘know.’ As such they are seen as a repository of clever things.
Initially there was much talk of specific areas of the brain responsible for each individual aspect of intelligence. However, the distinction between the two types of intelligence is not in brain structures. In 2014, Aron K. Barbey and his colleagues with the University of Illinois studied 158 human brain lesions of male patients who had an average age of 58, to investigate the neural foundations of key competencies for fluid intelligence and working memory. Although they found that both type of cognitive activities are active in the fronto-parietal network—a region of the brain on the top of the head above the ears—there were distinct patterns of activation for fluid intelligence and what they call working memory (crystalized intelligence).
However, none of these studies tested older adults or women. More importantly they have no predictive quality. Knowing which part of the brain is active most, does not inform you what the person is thinking. There might be distinct areas of the brain becoming more active depending on the type of task being performed rather than the type of thinking being used. It is likely that there are no distinct types of intelligence. It is also likely that only distinct tests we use to measure intelligence can be distinguished under two general types and that there are no distinct intelligence. There are also no different areas of the brain used for different types of intelligence. It could be that different tasks might use a part of the brain more than others. The variability among people is also under-reported. What might be activated in your brain might be different from how my brain reacts to the same task. This criticism is not to discount the value of doing fMRI studies, but to calm the generalization from these studies. The impression given is that there are distinct types of intelligence that use distinct areas of the brain. The corollary of this is that with aging brains we will see diminished capacity in some type of intelligence related to that part of the diminished brain. But this is not the case. To understand why this is not the case we have to go back to the beginning and explore how Cattell defined the two sets of intelligence in the first place.
The 1950s was a great time for psychology. While psychiatry was moving towards biology, pharmacology and brain surgery—using such barbaric but seemingly efficacious techniques such as prefrontal lobotomy, insulin shock therapy, and ECT; and while psychoanalyses shed its Freudian skin and was moving towards behavioral and cognitive therapy (later to morph into humanistic therapy); Psychology was being engulfed by the behaviorists and the emergence of statistics as the method of choice. The belief was that the human mind is a black box that we can never know. But through scientific rigor and with enough experimentation and statistical strength we can predict--but not understand--the black box. This was Cattell’s world. With sheer statistical strength we can force through a predictive model of the brain.
Using over 100 discrete tests for intelligence, Cattell put them all in a statistical hopper, shook them up, and saw which ones relate to each other. Using this method of defining clusters--called Factor Analysis--he defined two main groupings which he later called Fluid and Crystalized Intelligence. The clusters relate to the tests used, not to some innate distinction of intelligence. The expectation is that the breadth of the test used somehow represents the full capacity of our intelligence. By today’s standards, this assumption will be considered fanciful.
Once in the statistical hopper, how you determine what unique entities are related, and what unique entities are not related is by looking at their statistical loadings--how much they correlate with each other. If one test score is consistently high while another one is consistently low, then the analysis separates them as distinct. While if two test scores mirror each other, while one goes up the other goes up and then when one goes down the other goes down, then the two tests are related. Although this seems logical, in reality there are no real cut off point in their loading factors. How high and how low is determined not by the statistical analysis but by the researcher. Human judgement make that determination at what loading each variable is considered “in” or “out” of the Factor.
Recent work by the now deceased German gerontologist Paul Baltes and his colleagues demonstrated that older adults benefit markedly from guided practice in cognitive skills and problem-solving strategies. By focusing on the fluid ability, a small sample of 72 healthy older adults were capable of improving their fluid intelligence. They expressed improvement both by themselves and by following tutor-guided training. The ability to improve one’s fluid intelligence is not innate but a function of utility. Use it or lose it.
Practically, if older adults are shown to have an increasing capacity for crystalized intelligence then their need to use fluid intelligence diminishes. It is not that the ability diminishes, it is that their expertise in crystalized intelligence make reliance on fluid intelligence less essential. There are fewer opportunities to “wing it” when you know the outcome. The ageist view that somehow an aging brain losses its capacity for one of the most unknown features of intelligence—fluid intelligence, that capacity to create connections--reflects a shadow of the old eugenicists view that also denigrated older adults as diminished beings. Using these two concepts of Fluid and Crystalized Intelligence do not hold predictive power, and are useless in a clinical setting. It is time to remove the shackles of old eugenics legacy and stop using this ageist construct. Perhaps we can invest in research that starts to admire the model of reality that older people have created in their brain.
Cattell, R.B. (1941). Some theoretical issues in adult intelligence testng. Psychological Bulletin, 38, 592.
Barbey, A. K., Colom, R., Paul, E. J., & Grafman, J. (2014). Architecture of fluid intelligence and working memory revealed by lesion mapping. Brain Structure and Function, 219(2), 485-494.
Baltes P B, Lindenberger U, Staudinger U M (1998) Life-span theory in developmental psychology. In: Lerner R M (ed.) Handbook of Child Psychology: Vol. 1. Theoretical Models of Human Deelopment, 5th edn. Wiley, New York, pp. 1029–143
Baltes, P. B., Sowarka, D., & Kliegl, R. (1989). Cognitive training research on fluid intelligence
in old age: what can older adults achieve by themselves?. Psychology and aging, 4(2), 217.
Horn, J.L. (1965). Fluid and crystallized intelligence: A factor analytic study of the structure among primary mental abilities. Ph.D. Thesis. University of Illinois.
© USA Copyrighted 2016 Mario D. Garrett