There’s a comedy clip going around built on a simple punchline: men have billions more brain cells than women, so — case closed, women are smarter, because apparently more isn’t better. It’s funny. It’s also not how neuroscience actually works, and the real research is honestly more interesting than the joke.
Where Does This Claim Even Come From?
It’s not invented from nothing. The likely root of it is a real, peer-reviewed study: Rabinowicz et al., “Structure of the Cerebral Cortex in Men and Women,” published in the Journal of Neuropathology & Experimental Neurology in 2002, with University of Cincinnati neuropathologist Dr. Gabrielle de Courten-Myers as a co-author. The underlying findings were first presented at the American Academy of Neurology’s annual meeting in 1999, where ScienceDaily reported de Courten-Myers’ conclusion that “males possess more tightly packed and more numerous nerve cells (neurons)” in the cerebral cortex than females — while also noting that women had more neuropil, the tissue that allows those cells to communicate with each other. NPR covered a version of this finding in 2000, reporting a figure of roughly 2 billion more brain cells in men — but that NPR segment is a report about the research, not the scientific source itself. The actual peer-reviewed study is the real starting point, and it’s already more nuanced than “men just have more” — it also found women’s brain tissue had structural features (more neuropil, thicker cortex in places) that men’s didn’t. Numbers like these are almost certainly the real root of the “billions more brain cells” claim — simplified, exaggerated, and stripped of every caveat as they traveled from a research finding into a meme and eventually into a comedy bit.
Do Men’s and Women’s Brains Actually Differ in Size or Neuron Count?
Somewhat, yes — this part isn’t controversial. Multiple studies find that adult male brains are, on average, larger in total volume than adult female brains, even after adjusting for body size, with some analyses putting the difference in the range of 10%.
But total neuron count isn’t a simple story either. One often-cited study found women have proportionally more neurons than men specifically in the prefrontal lobes — the regions tied to language, judgment, and planning — even though men’s brains are larger overall. So “more cells” isn’t even consistently a male advantage once you look at where the cells are, not just how many there are in total.
Does More Brain Volume or More Neurons Mean More Intelligence?
This is where the joke — and a lot of pop psychology — falls apart. Research directly testing this question keeps landing in the same place: brain size and general intelligence are only weakly and inconsistently related, and that weak relationship does not reliably translate into a sex difference in actual measured intelligence.
A study published in the peer-reviewed journal Intelligence, using large adult samples, found males and females differed in brain volume but did not differ in general intelligence — the sex-based brain volume gap didn’t produce a corresponding IQ gap.
The strongest evidence on this point comes from a large, peer-reviewed study using UK Biobank data: Cox, Ritchie, Fawns-Ritchie, Tucker-Drob & Deary, “Structural brain imaging correlates of general intelligence in UK Biobank,” published in the journal Intelligence in 2019. Using brain scans and cognitive test data from over 29,000 adults, the researchers found a modest overall correlation between total brain volume and general intelligence (r = 0.276) — but critically, the strength of that brain-intelligence association did not vary by sex. In their own discussion, the authors noted that mean intelligence differences between men and women are “generally extremely modest or null” in the wider research literature, even though the brain-volume difference between the sexes is considerably larger — a pattern they suggest may exist because other, more specific brain characteristics compensate for the raw size difference. Other research in this space has been more mixed — a handful of older or smaller studies have reported small IQ differences favoring men in specific samples — but large, carefully controlled samples like UK Biobank tend to find the intelligence gap disappears or becomes negligible.
The Elephant in the Room (Literally)
Here’s a useful analogy for why total neuron count alone doesn’t tell you much about intelligence: if raw brain size or neuron count predicted intelligence, elephants should be running the world. A peer-reviewed study led by neuroscientist Suzana Herculano-Houzel found the African elephant brain contains roughly 257 billion neurons — about three times more than the human brain’s roughly 86 billion. And yet, obviously, elephants aren’t outperforming humans on cognitive tasks.
This isn’t a direct study of sex differences — it’s a cross-species comparison, useful specifically because it isolates the question of whether total neuron count, by itself, explains cognitive ability. The explanation researchers point to: it’s not the total neuron count across the whole brain that seems to matter most for complex cognition — it’s how many of those neurons are packed into the cerebral cortex specifically, the region most associated with higher-order thinking. In elephants, the vast majority of those 257 billion neurons are in the cerebellum, which handles movement coordination for an enormous body — not abstract reasoning. The human cortex, despite the whole brain being much smaller, actually contains more neurons than the elephant’s cortex does. Total brain size, in other words, is close to a red herring — which is exactly the same logical gap in the “men have more brain cells” joke, just demonstrated at a much larger scale.
Why This Kind of Comparison Is Scientifically Misleading
A few real reasons this “more cells = smarter” logic doesn’t hold up, according to the research above:
- Location matters more than total count. Neurons in movement-regulating regions don’t do the same job as neurons in the prefrontal cortex.
- Body size confounds raw brain size comparisons. Larger bodies generally need larger brains just to run basic biological systems, independent of intelligence — the same logic that explains why whales and elephants have bigger brains than humans without being smarter.
- Structure and organization matter, not just volume. Differences in cortical thickness, gray-to-white matter ratio, and neural density have all been proposed as explanations for why brain size differences don’t cleanly convert into intelligence differences between the sexes.
- The intelligence research itself is contested. Even researchers actively working in this field describe sex differences in general intelligence as, in their own words from one review, “technically the most difficult” question in the field to settle cleanly — a very different picture than a confident one-line comedy punchline suggests.
Population Averages vs. Individual People
Even in studies that do report small average differences — whether in brain volume, neuron count, or specific cognitive skills — these are population averages, not predictions about any individual man or woman. The range of variation within each sex, on basically every brain measurement researchers have looked at, is far larger than the average difference between the sexes. Knowing someone’s sex tells you essentially nothing reliable about their individual brain size, neuron count, or intelligence — the overlap between the two population distributions is enormous. A population-level average, even a real and replicated one, is not the same claim as “this individual man is smarter than that individual woman” — the research reviewed here doesn’t support that kind of individual-level conclusion, and none of the studies cited above claim to.
This is also a well-documented pattern across sex-difference brain research generally, not unique to this specific topic. A widely discussed 2022 analysis in The Conversation, written by a neuroscientist who reviewed three decades of human brain sex-difference research, found that once you set aside simple total size, almost none of the frequently claimed structural brain differences between men and women hold up consistently across different study populations — and the ones that do exist don’t reliably explain the behavioral or cognitive differences they’re often used to justify.
So, Are Men Smarter Than Women?
Based on the peer-reviewed research reviewed here: no, not according to any well-supported, consistently replicated evidence. Average brain volume differs somewhat between the sexes. Average general intelligence, across the largest and most carefully controlled samples, largely does not — and the relationship between brain measures and intelligence itself doesn’t appear to differ by sex either, per the UK Biobank findings. The billions-of-extra-cells claim is a real number, traceable to real, peer-reviewed research — it’s just being asked to do a job the science doesn’t actually support.
The comedy clip isn’t wrong that there’s a number in there somewhere. It’s wrong about what that number means — and so would a claim in the opposite direction, that this research proves women are smarter. Neither conclusion is what the science actually shows.
