Fluid intelligence peaks sometime in early adulthood. However, there is some recent evidence that we may be able to increase fluid intelligence during the teenage years. Recent research indicates that while the average IQ of those in the same age cohort is relatively stable, the IQ of an individual can change significantly during the teens. In a longitudinal study, 33 teenagers of average age 14.1 years were administered an IQ test and a structural brain scan in 2004 and then again in 2007, when their average age was 17.7 years. It was found that during this period, the average IQ of the group had changed very little; however about 20% of the participants showed a positive or negative change in IQ of at least 15 points (one standard deviation). Furthermore, magnetic resonance imaging (MRI) revealed that positive changes in IQ corresponded to increased gray matter in sections of the brain associated with those cognitive functions. Summarizing their findings, the researchers reported:
Our results emphasize the possibility that an individual’s intellectual capacity relative to their peers can decrease or increase in the teenage years. This would be encouraging to those whose intellectual potential may improve, and would be a warning that early achievers may not maintain their potential.
The citation for this research is: Ramsden, Sue. et al. 2011. “Verbal and non-verbal intelligence changes in the teenage brain.” Nature. Vol. 479. pp. 113-116.
After your fluid intelligence peaks, your crystallized intelligence–essentially acquired knowledge and skill–continues to increase your intellectual capacity. A recent study revealed that cognitive abilities such as vocabulary and comprehension continue to grow through our 30’s and 40’s and peak in middle age. Reporting their results, in 2015 the researchers stated.
Our results reveal considerable heterogeneity in when cognitive abilities peak: Some abilities peak and begin to decline around high school graduation; some abilities plateau in early adulthood, beginning to decline in subjects’ 30’s; and still others do not peak until subjects reach their 40’s or later.
The citation for that research is: Hartshorne, Joshua, K. and Laura T. Germine. 2015. “When Does Cognitive Functioning Peak?” Psychological Science. Volume: 26 issue: 4, pages: 433-443.
The highly intelligent people I’ve observed over several decades seem to be those who are immersed in intellectual pursuits like reading, writing, doing puzzles or mathematics, etc. However, I don’t know whether their high intelligence is a consequence of these activities or whether these activities are a natural consequence of high intelligence. I suspect it’s a combination of both.
