When it comes to the brain and the battle of the sexes, is bigger always better? Well, that’s been an area of research for many scientists. Many studies have found through imaging and post-mortem exams that men tend to have larger brain volume than women. This is true even when the numbers are adjusted for the fact that men have bigger body mass overall than women. The latest research on brain size differences between men and women is also the largest study to date. While the question of bigger versus better is unanswered in some areas, in terms of data and research, the larger the sample size, the more accurate results will be. In a study led by researchers at the University of Edinburgh, over 5,000 men and women had brain scans and while the research is awaiting peer review, it had some interesting results.
Most studies to date on the human brain have found that men have more brain tissue, in terms of sheer volumen, than women, but the results were not that specific and the sample sizes were too small. Most studies were only of 100 brains or so, not really enough for firm conclusions to be drawn. In addition there hasn’t been any research that specifically looked at which areas of the brain were larger or different between men and women.
Psychologist Stuart Ritchie, a postdoctoral fellow at the University of Edinburgh knew that big data was needed to really understand sex-based brain differences. UK Biobank, an ongoing, long-term biomedical study of people living in the United Kingdom was the answer. With 500,000 enrollees, there were thousands of possible study participants. Out of the UK Biobank study, Ritchie had 2,750 women and 2466 men, aged 44-77, enrolled in his research. MRI scans to measure the volume of 68 separate areas of the brain were conducted and in addition to general volume, cortical thickness was measured. The thickness of the cerebral cortex, the brain’s, curly swirly outer later, is believed to be related to cognition, memory, language and other brain functions.
The study results were adjusted for different age brackets, but they did show that women have thicker cortices than men, but overall, men have more brain volume. While there is research that correlates a thicker cortex to better scores on cognitive scales and intelligence tests, the focus of the team at Edinburgh was strictly size and structure. Regions other than the cortex, including the amygdala, the hippocampus, the thalamus and the striatum, were all larger in men than in women. Men also had a more variable range of cortical thickness, than women.
In an article posted n Sciencemag.org, Ritchie spoke about prior research that compared IQ in men and women and stated, “[That previous study] finds no average difference in intelligence, but males were more variable than females. This is why our finding that male participants’ brains were, in most measures, more variable than female participants’ brains is so interesting. It fits with a lot of other evidence that seems to point toward males being more variable physically and mentally.”
While there is still much to be debated about sex-based differences in the brain and what they actually indicate, the fact that this latest research has such a large amount of data is what makes it a significant advance in figuring out what brain size and gender could mean in terms of intelligence and behavior. Take a look at the video below to learn more about the project.