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Are Male Brains Different from Female Brains?

By Staff 1 year ago

CLAIM: MALE AND FEMALE BRAINS ARE THE SAME

PLAIN ENGLISH: The brains of males and females do not differ, and if they do, it is the result of environmental factors rather than innate differences.

RATING: MISLEADING

While it is true that male and female brains don’t differ fundamentally, it is misleading to state that male and female brains do not differ. Brains are complex organs that cannot be reduced down to a single factor. The differences between male and female brains, and also personality and behavior, are found in the correlational structure between many variables. Those claiming male and female brains do not differ are comparing them using improper univariate statistical methods when they should be instead take a multivariate approach. When multivariate analyses are used, male and female brains can be distinguished with high accuracy.

A DEEPER LOOK:

Few topics in science are more controversial than human neurological sex differences. The volatility surrounding this area of research results from a central fear: the fear of inequality. Many worry that the discovery of any innate neurological sex differences would embolden sexists and serve as a justification for discrimination. But if no such sex differences exist, it is thought, then discrimination would be entirely unfounded. Ignoring the problem of holding our fundamental human values hostage to future scientific discoveries, this fear has nevertheless resulted in some scientists and intellectuals downplaying sex differences or outright denying that such differences exist.

For instance, in 2019 Nature published a book review titled “Neurosexism: the myth that men and women have different brains.” The author, neuroscientist Dr. Lise Eliot, reviewed cognitive neuroscientist Dr. Gina Rippon’s 2019 book The Gendered Brain: The New Neuroscience That Shatters The Myth Of The Female Brain. In her review, Eliot writes that “...modern neuroscientists have identified no decisive, category-defining differences between the brains of males and females”.

Additionally, in a 2015 paper in PNAS by Joel et al. titled Sex beyond the genitalia: The human brain mosaic , the authors claim that sex differences were “mostly nonexistent or small” and that “human brains cannot be categorized into two distinct classes: male brain/female brain”.

Both of these articles received widespread media attention. According to Altmetric, these two articles combined appeared in 126 news outlets and were tweeted a total of 10,987 times. Vastly more attention than typical neuroscience papers.

But is it true that there is no such thing as a male and/or female brain?

To answer this question it’s important to first ask, “what evidence would be required to conclude the existence of male and female brains?” In the Nature and PNAS articles quoted above, I bolded relevant parts that indicate the authors’ requirements. In these quotes it is clear that in order for the authors to conclude that male and female brains exist as real natural categories, they must be reducible to “distinct” or “decisive, category-defining” differences. That is, male and female brains must boil down to some binary variable.

For example, the “sex difference” requirement for in the Joel et al. PNAS study required that traits be “dimorphic” (i.e. have very little overlap between males and females), and that “there should be a high degree of internal consistency in the form of the different elements of a single brain (e.g., all elements have the “male” form).” In other words, for the authors to conclude a sex difference exists, male brains must be typically masculine for every measured trait, and female brains must be typically feminine for every measured trait. With such a high threshold, it’s no wonder the study concluded male and female brains do not differ.

Univariate versus multivariate analyses

The issue with most studies concluding that male and female brains don’t exist is methodological in nature. In the above studies, the authors analyzed sex differences one trait at a time (i.e. using univariate analyses). But not all complex natural phenomena—such as male and female brains—can be accurately described by comparing single variables one at a time. Instead, some phenomena are best captured by the correlational structure between many variables (i.e. using multivariate analyses). Neurogeneticist Kevin Miller illustrated this concept well on his blog using male and female faces as an example:

Male and female faces differ on a wide range of parameters – size of the jaw, prominence of the ridge over the eyebrows, fullness of the lips, size of the bridge of the nose, and others. For each of these parameters, there is not a male form and a female form – there is a distribution, which is shifted one way in males and the other way in females. None of these markers by itself provides the means to accurately classify faces as either male or female. But taking all of them together certainly does. We are all very good at telling whether a face is male or female and computer programs can also very successfully perform this classification. So, “male” faces and “female” faces are clearly real things, even though the differences in specific parameters between them are not dimorphic.


Image from [clinicalgate.com]

The insistence that categories must be cleanly separable and reducible to a single essential factor in order for them to be considered real or “natural” categories is known as the univariate fallacy. Fortunately, this fallacy was quickly pointed out in several published responses in PNAS to the Joel et al. PNAS paper.

One of the responses by Jonathan Rosenblatt demonstrated that using only two variables, each exhibiting substantial overlap, that “a simple multivariate analysis using the same data suggests the opposite: Brains are indeed typically male or typically female” (see figure below).

In another response paper, Checkroud et al. , using different data but again only two variables, were able to distinguish between male and female brains with 93-95 percent accuracy and concluded that “multivariate analyses of whole-brain patterns in brain morphometry can reliably discriminate sex.” Several other papers come to similar conclusions: [nature.com] [onlinelibrary.wiley.com] [sciencedirect.com] [onlinelibrary.wiley.com] [sciencedirect.com]

Unfortunately, however, these responses did not receive nearly as much media attention as the original Nature and PNAS articles they debunked.

In conclusion, while male and female brain differences cannot be reduced down to a single binary factor, the claim “there is no such thing as a male and/or female brain” is misleading and the result of applying overly simplistic univariate statistics to a complex multivariate phenomenon.

What do you think?

Note: The views and opinions expressed in this article are those of the author and do not necessarily reflect the position of this website or its members.

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12 comments

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0

What female brain?

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Most human births are within the easily determined male or female. There are some that have physical characteristics of both which indicates that the development of sexual designation is complex and open to variables but the majority of births fall into the easily distinguishable female of male. There are differences in the way the brains of either sex work. One is not better than the other. They both are necessary for the development and evolution of species. Each specie evolved toward what was the most conducive to successful reproduction within the environment they live. Because of the comparatively long development of human offspring that is necessary for the development of our unique cognitive ability humans need a structure that protects the extended development.

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When the fetus is in an early stage developing the growth of the brain is slowed and the Corpus callosum is actually partly destroyed when the testicles of the male are developed. The Corpus callosum is the connecting tissue between the two lubes of the brain, this causes a lack of emotional response in the male. The amount of Testosterone released at this time determines the amount of emotional disconnect caused by this partial separation of the two lobes. This is the only physical difference in male and female brains that I know of and is why males are less emotional than females.

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An interesting article . I suppose one making such a study must take into consideration the plasticity of the brain and the effects that environmental, hormonal and experiential differences can make on the brain. For instance tumors that may cause a hormonal imbalance may cause differences. Chemicals in the environment through food, water and air quality can have an influence as well. Also if someone is subjected to longtime abuse whether physical, sexual or emotional abuse may cause not only physical but chemical changes in the brain which could cause a cascading event that would change the brain. All factors must be taken into consideration. So then, the only clear indicator of male/female brain differences would be examination of infant brains will little environmental factors to influence them and would have to be done in a sterile clinical sense that would, quite frankly, be unethical to begin with.

1

Well written. Crazy just how controversial this issue has always been, but I suspect for both good and bad reasons.

On a much lighter note: I really wish I had a "Nothing Box".

If you don't understand that particular wish, let me know.

I'm agnostic....

@tracycoyle My comment had nothing to do with religion. It was actually humorous. Attached is a quick video of an explanation of the male and female brain and its funny as heck. You will see why I'd like to have a "nothing" box.

@torontogal4388 Being agnostic means "I don't know".....just using it a play on the fact that I don't know what a 'nothing box' is.

@torontogal4388 Great video!!

@tracycoyle It is among my favs. That nothing box would certainly come in handy on the nights when your brain won't shut up and let you sleep LOL.

I do think he is absolutely right about the differences and, although I cannot quote studies I've read in the past (my bad), they can map brain activity that shows this to be the case and when the issue of real gender of a child is in question, the mapping is distinct enough to clearly show which brain wave patterns the child actually has.

When it comes to gender assignment or re-assignment I'm hoping this kind of brain scan is checked, as often children have other reasons for thinking they were wrongly sexed. Tom Boys are a classic case of this ... even more so when the child sees it is more beneficial to be one sex rather than the other. As I child I was very much a Tom Boy ... but am grateful no idiot was pushing that envelope.

4

I think this article provides a good example of why so many people these days are beginning not to trust "science." It is becoming more and more obvious all the time that the presuppositions of scientists have a great deal to do how they go about their work and influences the conclusions they reach, as the writer of the article has shown. Science appears in many ways to have been co-opted by politics and the culture war. In fact, many people see this happening with the current COVID-19 pandemic as well. Which "science" do we trust? Will the real Anthony Fauci please stand up? Etc.

4

The political desire to eliminate differences between the sexes is devoid of scientific support - even when scientists try to support the lack of differences. As the essay points out, methodology, along with intent, drive the failure to state all the relevant facts.

My experience is not scientific fact, but it informs the common sense that confronts 'conventional wisdom' that is being attempted to define or establish itself in societal discussions.

2

If there were no differences we would be the only species that has not specific differences, to perpetuate the species. The superficial debates had on these as social topics, make me stop thinking about the whole subject. Individual differences are also greater then ever given credit, for the furtherance of our species. That not a few, with their superior brains, like to rearrange the furniture of Society, is the only threat I see!

4

Why do we question whether there is a difference between men's brains and women's brains? We do not question whether there is a difference between men's bodies and women's bodies. Brains do not exist independent of their respective bodies. Men's brains do not have to coordinate and execute the same physiological processes as women's brains and vice versa. It seems to me that for physiologists to even suggest that there could be no difference indicates a fundamental scientific myopia.

Male and female brains are basically the same as it is in any animal.
What are they trying to prove?

@Lightman I suspect they're trying to assess a difference -or not- in cognitive ability between males and females. However what I was referring to was the brain as the controller of the autonomic processes of the human body. things that occur without our trying to make them occur. I'm sorry i don't remember who said it but a quote I've often thought of, "If the human brain was simple enough that we could fully understand it we would likely not be intelligent enough to ask the right questions about it."
I'm not referring to "genetic memory" either, necessarily. What I'm getting at and am too simple to state it more elegantly is that if we were able to completely understand the human brain I would be surprised to discover that the brain of a male innately had in it the capacity to regulate menses, ovulation, fertilization, fetal development and full term birth of a human child. This is not a cognitive activity but I'm pretty sure the brain is still somehow the master controller of the processes involved.

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1

Really?
I'd think everyone's brain is slightly different.

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