— Age & cognition
IQ at age 65 — what's typical?
IQ scores at age 65 are age-normed — meaning your raw test performance is compared against other 65-year-olds (or the closest reference cohort), then converted to a scaled score with population mean 100 and SD 15. The "average IQ at age 65" is therefore always 100 by construction.
Fluid intelligence has declined approximately 1 SD from 25-year-old peak. Crystallised intelligence may be at lifetime peak or slightly past. Processing speed substantially slower than at 25.
How IQ measurement works across ages
Modern IQ tests use age-normed scoring. A 10-year-old answering correctly on items that 12-year-olds typically get right scores higher than 100 (above their age-mates). A 30-year-old answering those same items correctly scores exactly 100 (typical for their age group). The score is always a comparison to peers, not an absolute capability.
Cognitive trajectories across the lifespan
- Fluid intelligence — peaks in early 20s, gradually declines 0.5-1 IQ point per decade after
- Crystallised intelligence — rises until 60s or 70s, then slow decline
- Processing speed — peaks early 20s, steepest age-related decline of any cognitive index
- Working memory — gradual decline from mid-30s onward
- Vocabulary, judgement, applied wisdom — typically rise through mid-life
How 65 compares to other ages
- IQ at age 12 — Early adolescence
- IQ at age 15 — Mid adolescence
- IQ at age 18 — Late adolescence / early adult
- IQ at age 21 — Young adult
- IQ at age 25 — Young adult