The graph below from Intelligence, IQ and Perception shows the relationship between fluid and crystallized intelligence as we age.
We observe that as we age, our fluid intelligence peaks in our early 20’s and goes into gradual decline. However, our crystallized intelligence acquired from our life experiences and our learning increases so that our total intelligence peaks somewhere in our 50’s (for most people).
The question posed here is, “Do those of higher fluid intelligence show greater gains in crystallized intelligence as they age?” That is, are people who are endowed with more fluid intelligence more likely to acquire more crystallized intelligence than average as they age? The answer to this question is suggested by some data collected by John Raven during the 1930’s.
In 1936, John Raven developed his Raven’s Progressive Matrices tests of intelligence. To norm these tests, i.e., establish baseline data on what scores adults could be expected to achieve as they age, he conducted widespread testing in the United Kingdom, Ireland, and Canada between 1939 and 1947. His graph of the Standard Progressive Matrix (SPM) scores for people of different ability levels between ages 20 and 65 is reproduced in the figure below.
Note: A person who scores at the 95th percentile of a particular age cohort has scored higher than 95% of all the people of that age. To be at the 95th percentile of the 20-year-old age cohort requires an SPM score of 55, while being at the 95th percentile of the 50-year-old age cohort requires only a score of 48.
The 50th percentile line in the graph shows that the average SPM score for 20-year-olds was about 43, while the average SPM score for 50-year-olds was about 33. This shows a substantial loss of cognition between a person of age 20 and a person of age 50, indicating that fluid intelligence is declining during that period. However, those who have lower fluid intelligence at age 20 decline faster (sharper downward slope in the graph) than those who have high fluid intelligence at that age. As they age, those with higher fluid intelligence will tend to learn faster, acquire more information, and increase their crystallized intelligence at a higher rate. More information on our productivity as we age is available at: In what ways do memory and intelligence change as we age?
