Could you look at a brain scan and reliably tell whether it came from a man or a woman? The answer is more complicated than you might expect. Research has found average differences in brain size and in certain regions, but the measurements overlap and no single feature defines a “male” or “female” brain. Using MRI, scientists study overall brain volume, cortical thickness and the hippocampus, a region involved in memory.
In this article, we’ll look at what the evidence says, why brain size can change how regional differences are interpreted, and how age, hormones and genetics may play a role. We’ll also tackle a common misconception: a larger brain does not automatically mean greater intelligence. By the end, you’ll know what brain scans can reveal and where the science calls for caution.
Yes, studies have found average differences in brain anatomy. A 2014 meta-analysis by Ruigrok and colleagues found that males have a larger average total brain volume. The researchers also reported differences in certain regions, including the amygdala, hippocampus and insula (research published in Neuroscience & Biobehavioral Reviews).
Here’s the important distinction: an average difference between two groups does not mean that every individual follows the same pattern. Some male brains have measurements that fall within the typical range observed in females, and vice versa.
That overlap is essential to understanding Gender differences in brain anatomy. To see why, it helps to look at the specific structures researchers measure.
One of the most consistently reported findings is that males have a larger average total brain volume.
But does a bigger brain mean a smarter person? Not necessarily.
A 2022 meta-analysis of more than 26,000 participants found a positive but modest association between brain volume and IQ. Brain volume alone therefore tells us very little about an individual’s intellectual abilities (study in Royal Society Open Science).
Brain size and intelligence are related research topics, but they are not interchangeable measures. Education, experience, genetics and many other factors contribute to cognitive abilities.
The cortex is the brain’s outer layer, involved in functions such as perception, language and thinking. Researchers examine its thickness, surface area and volume to understand how brain anatomy varies.
These measurements describe different features of the cortex. A finding about cortical thickness does not automatically mean that the entire brain region is larger or works differently.
Differences can also vary by location and age. This is why researchers examine multiple measurements rather than relying on one number to explain the male vs female brain structure.
The amygdala, caudate, thalamus, cerebellum and white matter have also been studied for average anatomical differences.
However, no single structure belongs exclusively to one gender. These findings describe patterns across groups, not a reliable way to predict an individual’s behaviour, personality or abilities.
One structure deserves a closer look because its findings illustrate just how much the details matter: the hippocampus.
The hippocampus plays an important role in learning and memory. Scientists also study it when investigating brain aging and conditions associated with memory changes.
So, when researchers compare hippocampus male vs female measurements, does one group consistently have a larger hippocampus?
The answer depends on how the researchers measure it.
A meta-analysis examining 68 matched samples, involving 4,418 participants, found larger average hippocampal volumes in males before adjusting for overall brain size. However, the difference was no longer statistically significant when researchers accounted for total brain volume or intracranial volume—the space inside the skull (Tan and colleagues, PubMed).
Why does this matter? A larger brain may naturally have larger regional structures. Comparing hippocampal volume without considering overall brain size can therefore give an incomplete picture.
Researchers are also looking beyond volume to examine hormonal status and genetic influences.
A 2024 study in Nature Communications analyzed MRI data from 1,093 healthy adults to investigate cortical and hippocampal microstructure. It found that the degree of some observed gender-related differences varied according to self-reported hormonal status in female participants, including menstrual-cycle phase and oral contraceptive use. These findings suggest that hormonal context may matter, but they do not establish that hormones alone caused the differences (read the study).
Genetics offers another perspective. A separate 2024 Nature Communications study examined the genetic architecture of more than 1,000 brain anatomy measures using UK Biobank data. The researchers found that genetic influences were broadly similar between male and female participants, although some regional differences emerged (read the genetic study).
This brings us to a wider question: how can scientists compare brain regions fairly?
Imagine comparing the size of a room in two houses. If one house is much larger than the other, the room measurements may partly reflect the difference in the size of the houses themselves.
Brain researchers face a similar challenge.
Total brain volume measures the overall size of the brain, while intracranial volume refers to the space inside the skull. Scientists may account for these measurements when comparing individual brain regions.
The hippocampus meta-analysis demonstrates why this matters. A difference seen in raw hippocampal volume was no longer statistically significant after adjustment for overall brain or intracranial volume.
But what is intracranial volume, and why does it matter?
Intracranial volume (ICV) refers to the space inside the skull, including the brain and surrounding fluids and membranes. Researchers use it as an estimate of overall head size when comparing brain structures. This matters because people with larger heads may also have larger brain regions, including the hippocampus.
By accounting for ICV, researchers can investigate whether a brain region is disproportionately larger or whether its size largely reflects overall head and brain size. In the hippocampus meta-analysis, the average difference between males and females was no longer statistically significant after researchers adjusted for ICV or total brain volume. This highlights why brain measurements need to be interpreted in context, rather than viewed in isolation
This also helps explain why studies do not always reach identical conclusions. Researchers may use different samples, MRI methods or statistical adjustments. Before comparing their findings, it is worth checking what each study actually measured.
A brain scan taken at age 20 does not provide the same picture as one taken at age 80. Brain anatomy changes throughout life, and age can influence measurements of both overall and regional volume.
Researchers are beginning to examine these patterns across much larger age ranges.
A 2026 preprint, Brain Charts for Neuroanatomical gender Differences Across the Human Lifespan, provides a broader look at how brain anatomy changes with age. Researchers analyzed 108,371 MRI scans from people ranging from mid-gestation to 99 years of age, examining 241 structural brain features, including regional volume, cortical thickness and surface area.
What did the researchers find?
The study found that gender-associated differences varied with age across nearly all the brain structures examined. These patterns remained even after researchers accounted for overall brain size. Interestingly, after this adjustment, approximately equal numbers of regions showed larger average measurements in males and females. The researchers also found greater variation between individual males in many brain measurements, while differences between the groups tended to become more pronounced with age.
These findings suggest that brain anatomy cannot be understood through brain size alone. Age and individual variation also matter when interpreting differences between male and female brains.
However, the results do not mean that male and female brains become two entirely separate types as people age. The study found substantial overlap between the groups, and the overall patterns of brain development remained broadly similar. Since the research is a preprint that has not yet been peer-reviewed, its findings should be considered emerging evidence rather than established scientific consensus. (research record in PubMed).
Because this work is a preprint, its findings should be treated as emerging evidence rather than settled scientific consensus.
The broader point is clear: age matters when interpreting brain measurements. A result from one age group should not automatically be applied to everyone.
There is no single explanation for all the differences researchers observe. Several influences may contribute, including gender chromosomes, hormones, brain development, puberty, aging and environmental experiences.
A 2024 Nature Communications study examined the genetic architecture of more than 1,000 brain anatomy measures. It found broad similarities in genetic influences between male and female participants, alongside some regional differences (read the study).
Hormones may also be associated with certain aspects of brain structure, as research into cortical and hippocampal microstructure suggests. However, association does not prove cause and effect.
The evidence points towards a complex combination of influences rather than one factor that determines how every brain develops.
This is where the findings need to be put into perspective.
Researchers can identify average differences in brain anatomy, yet considerable variation exists within both groups. The distributions of many measurements overlap, meaning a single feature cannot reliably identify every person as having a typically male or female brain.
Anatomical differences also do not automatically translate into differences in intelligence, personality or behaviour.
The phrase “male brain vs female brain” can make the distinction sound more absolute than it is. In reality, brain anatomy is varied, and group averages cannot describe every individual.
Understanding this overlap is just as important as identifying the differences.
Magnetic resonance imaging (MRI) allows researchers to study brain structures without surgery. Structural MRI can measure total brain volume, regional volume, cortical thickness and surface area.
With large datasets, scientists can compare measurements across thousands of people and identify patterns that might be difficult to detect in smaller studies.
However, MRI measurements require context. Age, scan quality, the method used to define a region and adjustments for total brain size can all affect the results.
MRI can help researchers identify statistical differences between groups. It cannot, on its own, establish a person’s intelligence or neatly divide all brains into two distinct anatomical categories.
So, do male and female brains differ? Yes, research has identified average differences in brain volume and certain brain regions. However, these findings do not tell the whole story.
Brain anatomy cannot be explained by gender alone. Genetic variation, hormonal status, age, development and environmental experiences can all contribute to differences in brain structure. Geographic background may also be relevant indirectly, through factors such as ancestry, nutrition, lifestyle and socioeconomic conditions. These influences can interact, making each person's brain unique.
The evidence also shows why measurements need context. For example, differences in hippocampal volume may change when researchers account for intracranial volume, while large-scale studies suggest that patterns of brain anatomy can vary across the lifespan.
Ultimately, male and female brains share many similarities, alongside measurable average differences and substantial individual variation. Rather than attributing every difference to gender or asking which brain is better, researchers aim to understand how biological, developmental and environmental factors work together to shape brain anatomy.
Research has identified average differences in overall brain volume and certain regional structures. Considerable variation and overlap exist between individuals.