Question
At what age does intelligence peak?
Short answer
There is no single peak age. Processing speed and some reasoning measures peak in the late teens and twenties, while vocabulary and accumulated knowledge keep rising into the sixties. Because IQ is scored against your own age group, these shifts do not, on their own, change your IQ score.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
Different abilities, different peaks
A large study by Hartshorne and Germine found that cognitive abilities do not rise and fall together. Processing speed and some reasoning measures peak in the late teens and twenties; vocabulary and accumulated knowledge keep rising into the sixties (Hartshorne & Germine, 2015). Salthouse reported a similar pattern (Salthouse, 2009).
This fits Raymond Cattell's split between fluid intelligence, reasoning with new problems, and crystallized intelligence, what you have learned (Wikipedia: Fluid and crystallized intelligence). Fluid tasks favor speed and novelty, which peak early. Crystallized tasks favor experience, which keeps building. The guide fluid vs crystallized intelligence explains both.
Try one · Spatial Reasoning
Which option is the same shape, only rotated?
Tap the option you think is right, or show the answer.
Show the answer
Option 1 is the original figure turned a half turn.
How to solve it
- Pick a landmark: the marked cell or the end of the longest arm.
- Turn the figure in your head and watch where that landmark goes, and which side the other cells end up on.
- Turning the figure a half turn gives option 1.
- Each of the other options is a mirror image: flipping it over would match, but no turn does.
That was 1 puzzle. The full test has 25.
Why your IQ score does not have a peak
Modern tests compare you with people your own age (Wikipedia: Intelligence quotient). If everyone your age is a bit slower than they were at 25, the comparison moves with them. So an average 60-year-old scores 100, just like an average 25-year-old. Read does IQ decline with age for more on this.
What this means in practice
- Timed visual puzzles, like those on IQ Octopus, lean on speed and fluid reasoning. Age norms on a careful test account for that.
- Knowledge-heavy tasks may feel easier with age, and the research supports that feeling.
- A slower pace with age is normal. The glossary entry on processing speed has more.
For the full research picture, see the guide to IQ and age.
Sources
- Hartshorne, J. K., & Germine, L. T. (2015). Psychological Science, 26(4), 433-443. doi.org/10.1177/0956797614567339
- Salthouse, T. A. (2009). Neurobiology of Aging, 30(4), 507-514.
- Fluid and crystallized intelligence. Wikipedia. en.wikipedia.org/wiki/Fluid_and_crystallized_intelligence
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient