IQ is set at around 20-years-old and later effort will not improve it much, recent research finds.
The complexity of people’s jobs, higher education, socialising and reading all probably have little effect on cognitive ability.
Naturally, these activities have many other benefits, but little influence on IQ.
However, education is particularly important at an early age when the brain is still developing.
By early adulthood, though, most people’s IQ has settled down.
While some studies have suggested that cognitive activities in later life can improve IQ, Professor William S. Kremen, the study’s first author, thinks otherwise:
“The findings suggest that the impact of education, occupational complexity and engagement in cognitive activities on later life cognitive function likely reflects reverse causation.
In other words, they are largely downstream effects of young adult intellectual capacity.”
The study included 1,009 men now in their 50s and 60s whose IQ was assessed when they were around 20-years-old.
They were given tests of abstract reasoning, verbal fluency and memory, among with other cognitive measures.
The results showed that most of the difference between the men’s IQs in mid-life was explained by the difference between them at around 20-years-old.
In comparison, the complexity of the job they had, the intellectual activities they engaged in, and their education in the meantime hardly had any effect on their IQ.
Brain scans also showed that IQ at age 20 was associated with the surface area of the cerebral cortex.
The cerebral cortex is the brain’s gray matter, the part that performs the higher functions of thinking, perceiving and language.
Most of the benefits of education for IQ likely happen before young adulthood, said Professor Kremen:
“Our findings suggest we should look at this from a lifespan perspective.
Enhancing cognitive reserve and reducing later life cognitive decline may really need to begin with more access to quality childhood and adolescent education.”
The study was published in the journal PNAS (Kremen et al., 2019).