When Does IQ Peak?
A study conducted by psychologists and neuroscientists based on chess skills indicates that chess performance is an important indicator of cognitive ability and the capacity to learn from experience.
Data shows that during childhood and adolescence, the skill rapidly improves. It continues with minimal improvement until age 20 and reaches its peak by the age of 35, then begins to mark a decline at 45.
Our ability to process information and speed visualization, which we call "fluid intelligence," decreases as we age, but tasks based on experience and accumulative learning (crystallized intelligence) improve.
When Does IQ Stabilize?
The American psychologist James C. Kaufman says crystallized intelligence reaches 98 by age 20-24, reaches 101 by 35-40, and then drops to 100 (45-60), then 98 (5-54), then 96 (65-69), then 93 (70-74), and 88 (75+), whereas fluid intelligence drops way faster. As Kaufman explains, it peaks between the ages of 20 and 24 (100), after which it gradually decreases to 99 (25 to 34) and 96 (35 to 44) before experiencing a rollercoaster plunge to 91 (45 to 54), 86 (55 to 64), 83 (65 to 69), 79 (70 to 74), and 72 (75+).
Based on the information provided above, it appears that an individual's IQ is fixed at the age of 20.
When Does IQ Stop Increasing?
The IQ of an individual is never supposed to change with age since the test is performed in comparison to the IQ of other individuals of the same age group. Aside from the fact that IQ does not change as the person ages, on average, fluid intelligence does decline, starting at age 45. Added experiences and later efforts like the complexity of people’s jobs, higher education, socializing, and reading have little influence on IQ.