Does size matter? Pink brains blue brains.


Image thanks to MARIE CLAIRE MagazineYawn

So women have smaller brains than men. It’s hardly surprising really.

They also have smaller feet, hands, noses, ears, hearts, lower red blood cell count, lower base metabolic rate, less muscle mass and height.

Among other things.

The highbrow term for these kinds of differences is Sexual Dimorphism.

Neil Sears wrote about male/female differences a couple of months ago, identifying that, on average, a woman’s brain is 8% smaller than a man’s.

Curiously, women are about 8% shorter than men too, on average. Knowing about sexual dimorphism as you now do, you’d have to say that it makes perfect sense for a woman’s brain to be smaller than a man’s.

Women are smaller than men. Period.

Big is good. No?

But we do know that size IS important, insofar as the amount of brain cells and, especially, the number of connections between cells, matters. It matters a lot. Quantity and connectedness are critical.

And although we might struggle to say that a woman’s hands and feet are less effective than a man’s because they are smaller, is it a different story when we come to the brain? Does a smaller brain make a difference?

Let’s start from the very beginning…

Differentiation between boys and girls begins at conception. It’s the Dad who determines whether children are girls or boys, because the Dad (sex chromosomes XY) can donate either an X or a Y sex chromosome. Mom (sex chromosomes XX) always donates an X sex chromosome. The baby is XY (boy) or XX (girl), depending on which sex chromosome it inherits from dad to go with the X from mom.

Anatomically though, you can’t tell if a fetus is a boy or a girl until after about 12 weeks from conception. Although external genitals begin to develop from 6 weeks in utero, both boys and girls look the same. The same tissue later develops into the differentiated sex organs of boys and girls.

It’s why the organs differentiate that is of interest to us.

Hormones 1

From about 12 to 18 weeks, a boy baby will release a massive hormone surge. These hormones get straight to work defeminizing him (making sure he doesn’t develop into a girl) and masculinizing him (making sure he does develop into a boy). Both processes are required.

These are staggering, widespread changes, and create irreversible effects, with massive impact on the brain, and give rise to the traits, behaviors and characteristics we recognise as male.

Girl babies don’t get this hormone surge, so being a girl is, if you like, nature’s default setting. Stuff has to happen to a fetus to make it a boy. If a boy baby doesn’t get this hormone surge, he will be a boy by chromosome (an X from mom and a Y from dad) but anatomically female, or indeterminate, because he wasn’t defeminized and wasn’t masculinized.

Hormones 2

About three months after birth, boys get another massive hormone dose.

Don’t underestimate how much these surges flood this immature brain and cause change. Moreover, because there are extra, complicated steps to make sure a fetus becomes a boy, there is much more opportunity for things to go wrong. For example, more boys develop schizophrenia, learning difficulties, language difficulties, autism spectrum disorders and antisocial personality disorder.

Subsequent gender differences in behaviour seem obvious to everyone. Boys and girls play differently, compete differently, communicate differently and so on.

No surprises, boys are different from girls.

And girls end up with a smaller brain.

So what?

Can this explain some of our common psychological understanding? Is a smaller or larger brain responsible for differences we experience?

And while we’re here, can women multitask better than men? Are men better at parallel parking or reversing cars than women? What about women’s intuition?

Neil Sears said that the woman’s brain was smaller, yes, but also more efficient, especially in the region of the hippocampus, a critical memory structure. Whereas in men a larger structure indicated higher intelligence, this wasn’t true of women. Rather, greater connectivity suggested that women can achieve the same as men, with fewer brain cells and less effort.

Ask any woman and she’ll tell you that she already knew that…

Moreover, recent work out of Penn Medicine, published in the Proceedings of the National Academy of Sciences, found males had greater neural connectivity from front to back, and also within one hemisphere, whereas in women the wiring was stronger between hemispheres.

Ragini Verma, PhD, an associate professor in the department of Radiology at the Perelman School of Medicine at the University of Pennsylvania, notes “These maps show us a stark difference—and complementarity—in the architecture of the human brain that helps provide a potential neural basis as to why men excel at certain tasks, and women at others”.

For men, the connections link the perception and coordination areas, suggested they excel at coordinated action. Women show stronger communication between the analytic and the intuitive, by which they mean the left and the right hemispheres respectively, demonstrating strengths in emotional processing and inferring the actions of others in social situations.

The authors observed only a few gender differences in the connectivity in children younger than 13 years, but the differences were more pronounced in adolescents aged 14 to 17 years and young adults older than 17.

Hormones 3

These age-related observations fit with the third major hormone surge, also called puberty. Naturally, girls get this too, and both bodies and brains change again. During this time, brains undergo a rapid growth in brain cells. They proliferate in number, before being pruned back to then remain at a relatively stable number throughout life.

The Penn researchers would further argue that these connectivity differences can also suggest that men are probably better at single focused task as cycling or navigating directions which require greater spatial awareness. The hippocampus, a key structure investigated in Sears’ article, is also partly responsible for navigation.

Women, with their different connectivity, better memory and social skills, are better suited to group solutions and multitasking, the researchers say.

So perhaps we can say, with some assurance from Penn, that men are generally spatially stronger, and women better socially. Neil Sears also puts men as better spatially, and women better at inductive reasoning and tracking changes. This may well explain the sex battles over parallel parking (win for the boys) and multitasking (win for the girls).

As a caveat, we should note that these are generalities and these (and all) abilities lie on a continuum, with people spread along that continuum from one end to the other, including women who are spatially better than men and men who better at inductive reasoning than women, and so on.

So where are we?

So let’s agree with Neil Sears and sexual dimorphism that men have larger brains.

Let’s agree that men and women have different abilities.

Let’s agree that a brain bathed in testosterone at three critical periods is going to change the brain in substantial ways.

Then let’s agree that we’ve oversimplified and not even allowed for the complexity of genes, the fact that experiences can turn genes on and off, that diet, sleep, exercise, poverty, maternal diet, paternal diet, birth order and a million other things impact the quantity and connectivity of your brain.

And let’s agree that it isn’t simply a matter of size.

A well-connected female brain is going to be better than a poorly connected male brain, regardless of size. Albert Einstein, for example, despite his seemingly large head, had a smaller than average brain. By and large, we consider him pretty smart.

So here’s the take home bit

It’s the connectivity that is critical.

100 cells, connected only once each, is a much smaller network, with much less ability to function, re-route information, and remember, than 50 cells connected 25 times each. Men and women have brains that are connected in different ways. Assuming you eat well, get enough sleep, and exercise a bit, developing connections between brain cells by stimulating the brain is the key to efficiency, shaping intelligence, and brain longevity.

What we should be asking, is not whether one brain is better than another, but how do we make our own better.

A postscript…

While we’re talking about boys and girls, two things.

Women’s intuition is not a mysterious superpower. It is most likely the result of greater lateral connectivity and social awareness, allowing them to recognise patterns better than men. It’s not mysterious, it’s a skill.

And for the record, and though it is something we don’t seem ready to believe, men talk as much as women. Yes, fellas, you do 🙂

Impressive words to drop into the morning coffee chat

Hippocampus

What do you think?

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About brendonbclark

Hi, I’m Brendon, but people usually call me B. I’ve a Masters degree in psychology, postgraduate qualification in mental health, and qualifications in counselling, professional supervision and adult education. I consult, speak and blog. Join me, you can subscribe for free.
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