Male vs Female Brain Development: What Changes by Age
Girls' total brain volume peaks at 10.5 years and boys' at 14.5. In 5,216 UK adults the brain-volume gap is 1.41 standard deviations and the reasoning-test gap 0.18. Group averages only, with considerable overlap.
What you need to know
- Male vs female brain development follows different timetables. Total brain volume peaks at 10.5 years in girls and 14.5 years in boys. Grey matter peaks 1 to 2 years earlier in girls (Lenroot and colleagues, 2007; 829 scans, 387 people).
- Across everyone, grey matter volume peaks near 5.9 years, subcortical grey matter near 14.4 and white matter near 28.7 years (Bethlehem and colleagues, Nature, 2022; 123,984 scans).
- In 5,216 UK adults aged 44 to 77, men's total brain volume was about 10.6% larger (d = 1.41). A short reasoning quiz differed by only 0.18 SD.
- These are group averages with considerable overlap. Two of the three papers warn against reading size differences as differences in ability, and none measured causes.
Girls' and boys' brains follow different timetables. Total brain volume peaks at 10.5 years in girls and 14.5 years in boys (Lenroot and colleagues, 2007; 387 people aged 3 to 27). In adults the averages differ too, but the groups overlap considerably. In 5,216 UK adults, men's total brain volume was about 10.6% larger. Yet the gap on a reasoning test was only 0.18 of a standard deviation (Ritchie and colleagues, 2018).
The new finding comes from reading two papers side by side. In those same 5,216 adults, the brain-volume gap is about eight times the reasoning-test gap (1.41 against 0.18 standard deviations, our arithmetic). Below: how male vs female brain development changes by age, what the adult data show, and what group averages cannot tell you about any one person.
What is the difference in male vs female brain development?
The main difference is timing. Lenroot and colleagues (NeuroImage, 2007) scanned 387 healthy people: 178 girls and women and 209 boys and men. They scanned each person up to seven times, 829 scans between ages 3 and 27. They plotted size against age instead of comparing broad age bands.
- Total cerebral volume peaked at 10.5 years in females and 14.5 years in males
- Cortical and subcortical grey matter followed an inverted U, with peak sizes 1 to 2 years earlier in females
- White matter kept increasing across the whole 24-year span, with a steeper rise in males during adolescence
- Mean total cerebral volume was about 10% larger in males, as earlier studies also found
That is a four-year gap. By our reading of the two peak ages, at age 12 a typical girl's total volume is already past its peak, while a typical boy's is still rising. The authors add a warning in the paper: differences in brain size "should not be interpreted as implying any sort of functional advantage or disadvantage". An earlier peak does not mean an earlier finish line, and a bigger volume does not mean a better score.
How does the brain change by age?
Brain development by age has no single finish line. Bethlehem and colleagues (Nature, 2022) pooled 123,984 scans from 101,457 people in more than 100 studies. The people ranged from 115 days after conception to age 100. The team fitted separate curves for females and males.
- Age 5.9: total cortical grey matter volume peaks (95% confidence interval 5.8 to 6.1), then declines almost in a straight line
- Age 10.5 and 14.5: total cerebral volume peaks in girls and boys (Lenroot and colleagues, a separate sample)
- Age 14.4: subcortical grey matter peaks (14.0 to 14.7)
- Age 28.7: white matter volume peaks (28.1 to 29.2), with a faster decline after age 50
So the answer to "when does the brain stop developing?" is that it depends on the tissue. Grey matter volume peaks in early childhood, subcortical grey matter in the mid-teens and white matter near 29. The Bethlehem authors state that larger absolute volumes in males are not indicative of any difference in clinical or cognitive outcomes. For the thinking side of this timetable, see at what age intelligence peaks and our peak brain age study.
Do male and female brains differ in adults?
On average, yes, in some measures, with considerable overlap. Ritchie and colleagues (Cerebral Cortex, 2018) scanned 2,750 women and 2,466 men aged 44 to 77 in the UK Biobank. They compared the two groups on a large set of brain measures.
- Total brain volume: 1,115.8 cm3 in women (SD 89.7) against 1,233.6 cm3 in men (SD 98.3), a standardised gap (Cohen's d) of 1.41
- Grey matter 597.0 against 643.5 cm3; white matter 518.9 against 589.6 cm3
- Cortical thickness: women had thicker cortex in 47 of 68 areas (mean d 0.22), 20 areas showed no difference, and only the right insula was thicker in men
- Variance: men varied more on the raw volumes (women's variance averaged 0.82 of men's)
- Body size: the men were also much taller on average (d = 2.15)
Cohen's d says how many standard deviations apart two averages sit. If both groups followed a normal curve, a d of 1.41 means the two curves overlap by about 48%. A randomly chosen man would have the larger brain in about 84 pairs out of 100 (our arithmetic). Most of the subcortical differences were tied to total brain size: adjusting for it cut the d values by 85.0% on average.
Here it is in natural frequencies, using the means and SDs in the paper's Table 1. About 9 in 100 women have a larger total brain volume than the average man. About 12 in 100 men have a smaller one than the average woman (our arithmetic, assuming normal curves). The groups differ on average, and still share a wide middle.
Does a bigger brain mean a higher IQ?
These data do not show it. In the same 5,216 people, Ritchie and colleagues gave a short verbal-numerical reasoning quiz (maximum score 13). Women averaged 6.80 (SD 2.10) and men 7.14 (SD 2.13), a gap of 0.18 SD. Reaction time differed by 0.21 SD, in favour of men.
A 0.18 SD gap overlaps by about 93%, and a randomly chosen man would score higher in about 55 pairs out of 100 (our arithmetic). On an IQ-style scale with an SD of 15, 0.18 SD would be about 2.7 points. That is only an illustration, because this quiz is not an IQ test. Our IQ percentile calculator shows what a gap of a few points means. For the IQ question itself, read IQ tests and gender differences and the brain size and IQ report.
In the same 5,216 adults, the brain-volume gap is about eight times the reasoning-test gap.
What do these studies not show?
They show group averages, not individuals. Within each sex the spread is wide (an SD of about 90 to 98 cm3 in total brain volume), and the two ranges overlap. They also leave out much of life.
- Lenroot and colleagues studied healthy volunteers from one US research programme, screened for psychiatric and medical conditions. The IQ listed in their Table 1 averaged about 112 in girls and women and 114 in boys and men, so the sample sat above average
- Ritchie and colleagues studied volunteers aged 44 to 77 at one point in time. They cannot say how the adult gaps arose in childhood
- Bethlehem and colleagues note that MRI studies are biased relative to the diversity of the global population
Where would your own score land?
Group averages describe groups. Your own reasoning score describes you.
Find your IQ score now! →To see where your own score sits on a scale with a mean of 100, take the IQ Metrics IQ test. For the scans of unusually high scorers, see what the gifted brain scans show.
Common questions
What is the difference between male and female brain development?
The main difference is timing. Total brain volume peaks at about 10.5 years in girls and 14.5 years in boys, and grey matter peaks 1 to 2 years earlier in girls (Lenroot and colleagues, NeuroImage, 2007; 387 people aged 3 to 27). White matter rises faster in boys during adolescence.
At what age does the brain stop developing?
It depends on the tissue. In a pooled sample of 101,457 people, grey matter volume peaked at 5.9 years, subcortical grey matter at 14.4 years and white matter volume at 28.7 years, with a faster decline after 50 (Bethlehem and colleagues, Nature, 2022).
Are male and female brains different sizes?
On average, yes. In 5,216 UK adults aged 44 to 77, men's total brain volume averaged 1,233.6 cm3 and women's 1,115.8 cm3, about 10.6% larger in men, but the distributions overlap considerably (Ritchie and colleagues, Cerebral Cortex, 2018).
Do these brain differences mean a difference in intelligence?
No study here shows that brain size differences produce differences in intelligence. The Lenroot authors say size differences should not be read as a functional advantage or disadvantage, and the Bethlehem authors say larger male volumes are not indicative of any difference in cognitive outcomes. In the 5,216-person sample a short reasoning quiz differed by 0.18 SD, and that quiz is not an IQ test.
Sources for this story
- Lenroot RK and colleagues. Sexual dimorphism of brain developmental trajectories during childhood and adolescence. NeuroImage 36 (2007), doi 10.1016/j.neuroimage.2007.03.053 — Elsevier
- Lenroot et al. 2007, author manuscript with Methods and Table 1 (PMC2040300) — National Library of Medicine
- Ritchie SJ and colleagues. Sex differences in the adult human brain: evidence from 5216 UK Biobank participants. Cerebral Cortex 28 (2018), doi 10.1093/cercor/bhy109 (Table 1 on PMC6041980) — Oxford University Press
- Bethlehem RAI and colleagues. Brain charts for the human lifespan. Nature 604 (2022), doi 10.1038/s41586-022-04554-y — Springer Nature
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