Women Have Small Brains and Other Biases of Science

But we must not forget that woman are, on the average, a little less intelligent than men, a difference which we should not exaggerate but which is, nonetheless, real. We are therefore permitted to suppose that the relatively small size of the female brain depends in part upon her physical inferiority and in part upon her intellectual inferiority.

-Paul Broca

Paul Broca 1824-1880

Back in the mid 1800’s there lived a professor named Paul Broca. His work on the brain was instrumental in brain anatomy and anthropology. He determined the part of the brain associated with speech, revolutionizing our understanding of human speech. His work was thorough, and he was ahead of the times in his scientific thinking. However, even the best scientists can be influenced by social bias.

Paul Broca performed measurements of cranial sizes of male and female skulls, and found that the female cranial size was smaller. Was the measurement correct? Well, to a certain extent, yes. Yet, the problem with the study was his conclusion. A great summary of some of Broca’s study can be found in this essay by Stephen Jay Gould (PDF). The issue is that there are numerous factors that may lead to intelligence, and not all are linked to brain size. In fact, with newer technology, we have also found that it is neural connections within the brain which make a great contribution to intelligence.

Female Brains Are Still Smaller

Now, the time of Paul Broca was very different from modern day. You would think something like using brain size to prove women are less intelligent would be a thing of the past. Not necessarily. A study from 2006 by Philippe Rushton claimed that men were on average smarter than women due to brain size. This debate was still going on in 2006.

This same author published a paper in 2002 citing differences in brain size in different races are what cause the IQ differences. The paper, called “Brain size, IQ, and racial-group differences: Evidence from musculoskeletal traits,” in which the concluding sentence of the abstract states “brain size-related variables provide the most likely biological mediators of the race differences in intelligence.” [Rushton, 2002].

When coming to scientific conclusions, it is important to remember that correlation does not imply causation.

The ultimate problem with studies like these is that they completely disregard cultural and societal contributions to intelligence. For instance, we are just now coming into a time where more women are applying to college than men, and more equal opportunities are available to minorities and women.


To end, I leave you with the most recent tidbit of information I could find. For the first time in recent history, women are scoring higher on IQ tests than men.

So much for that publication citing the reason for women’s lower IQ scores was due to their brain size.

10 responses to “Women Have Small Brains and Other Biases of Science

  1. I bet that if they’d found that female brains were shaped like stars, and male brains were shaped like moons, they’d draw the conclusion that moon-shaped brains signaled greater intelligence. I find that ingrained gender biases are the biggest obstacle to good science :(

    • Things like this just go to show how difficult it is to break away from perceived gender differences. Scientists are supposed to think outside of general societal perceptions of the world when looking at data, but it is difficult to think outside and beyond ideals that you have been raised with on your own.

  2. Great round-up – am looking forward to reading the Stephen Jay Gould article. have you read this book The Mismeasure of Man? I’m a few chapters in and it’s RIVETING.

  3. Let’s see. Basketball players are the tallest, and have the biggest brains. But they aren’t all rocket scientists.

  4. I’m down with being stupider than men if men are willing to cop to being stupider than elephants, most whales, and… um… bison maybe? I’m not really up on brain sizes across a broad taxonomic range, but I’m pretty sure I can write a better essay than a humpback whale, even if the whale can sing better than I can.

    • Humans do not even have the largest brain to body mass ratio, let alone the largest brains as you pointed out. It seems that the more we delve into the neuroscience side of things, the less these rudimentary measurements of brain size tell us.

  5. I’m a little late in reading your earlier posts. I see someone has already beat me to recommending The Mismeasure of Man. It’s remarkable that scientists have also determined that that shape of a person’s head is a direct measure of criminality and that Italian courts recognized this fact in determining which of two identical twins committed a murder. Or that the U.S. Supreme Court found that lack of education and opportunity is hereditary and is grounds for forced sterilization (Carry Buck).

    But you have to admit that intelligence is measured directly by the size of one’s muscles and more precisely by the size of one’s penis. I think Broca was well aware of this undisputed fact. There’s just so much science I don’t yet understand, but fortunately we have court systems to let us know what is valid.

    • Yes, the courts always know best about what constitutes science. Also, thankfully we have politicians and news pundits that know all about science as well, and can teach us about this confusing subject.

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