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A Photo of Your Gay Brain July 12, 2009

Posted by Geekgirl in brain.

Blood flow in the brain

Blood flow in the brain

Take a look at this photo and compare the brains. HeM means heterosexual man, HeW means heterosexual woman, Hom  means Homosexual man and HoW means homosexual woman. If we were using these photos of  brains to tell us gender, instead of our genitalia, who would you call a boy or a girl?

See the red and yellow areas? In the left amygdala, the heterosexual male brain looks very similar to the homosexual female brain. The heterosexual female brain looks very similar to the homosexual male brain. The right amygdala does not show this clear cut pattern but it is clear that there is a difference between heterosexual and homosexual men.

So where did this picture come from and what does it show?

Researchers in Sweden studied the symmetry and connectivity of the brains of straight men, straight women, gay men and lesbians. This work was published in April 2008 in the very prestigious journal Proceedings of the National Academy of Science. The original reference is:

PET and MRI show differences in cerebral asymmetry and functional connectivity between homo- and heterosexual subjects.

Authors Ivanka Savic* and Per Lindstrom

Stockholm Brain Institute, Department of Clinical Neuroscience, Karolinska Institute, 171 76 Stockholm, Sweden. PNAS April 2008.

The study itself is highly technical and not easy reading for us every day folks without this level of training. However, it can be translated into terms we can all understand. The researchers asked two main questions. Are the two halves of the brain symmetrical or asymmetrical with respect to volume? Are there differences in functional connectivity between the two halves of the brain?

The researchers chose to measure connections in the amygdala because that section of  the brain has a high density of estrogen and androgen receptors. Androgens are testosterones and  related hormones. A receptor allows the hormone to enter into the cells. They also chose the amygdala because of earlier research that shows this area correlates to sex and  sexual orientation.

The study used ninety subjects. 25 heterosexual men, 25 heterosexual women, 20 homosexual men and 20 homosexual women. The difference in the number of subjects is not statistically significant.

The brains were analyzed using PET measurements of blood flow to measure functional connections between the two halves of the brain. In this case, a picture is able to replace a lot of words.

The researchers also looked at the volume of each half of the brain using MRI. The paper shows the variation in the data and the statistics proving the differences. For the sake of simplicity, I’ll just include the result.

Left     Half

HeM 25           624      612      These are significantly different.

HeW 25           581      581      These are not significantly different.

HoM 20           608      609      These are not significantly different.

HoW 20          548      543      These are significantly different.

Again, we see the same pattern. Heterosexual men and  homosexual women have significantly different brain volumes from one side of the brain to the other. The heterosexual women and the homosexual men have equal brain volumes.

In other words, gay men have brains that are more like straight women than straight men. And lesbians have brains that are more like straight men than straight women.

The authors concluded that “The present study shows sex-atypical cerebral asymmetry and functional connections in homosexual subjects. The results cannot be primarily ascribed to learned effects, and they suggest a linkage to neurobiological entities.”

Now, does this study prove that these differences are the cause of sexual orientation? One study alone doesn’t do that. But it is very clear that the brains of straight people and gay people are different. Not only different, but straight men and lesbians share similarities and straight women and gay men share similarities.

Let’s think about this from a different angle. If people choose to be gay, how could their brains change by making this choice? That doesn’t make any sense – and I don’t think you have to be a scientist to understand that logic.



1. Paul - July 12, 2009

This study is anti-gay. The results are wrong. According to their propoganda gay people have smaller brain volume than haterosexuals. No way. Gay men and lesbian women are much more likely to earn a degree than heterosexuals. There is a correlation between above average IQ and earning a degree.

2. lgbtlatestscience - July 12, 2009

Hi Paul
I think you misunderstood. They are comparing the volume of one side of the brain to the other side, not between straights and gays. You’ll notice women have the smallest brain volumes. I’ve never heard of any correlation between brain volume and intelligence. This paper never mentions intelligence at all. It is only looking at differences in the brain. Left handed people have asymmetrical brain volumes.

The researchers are neither pro-gay nor anti-gay. But the research clearly shows that straight people and gay people have different brains. This provides some basis for the belief that being gay is not a choice. The photo shows more blood flow between the two sides of the brain in straight women and gay men. More blood flow between the two halves does allow the two halves to work in sync better.

You are correct, gays are more likely to get advanced degrees. I have a paper about that topic and will blog it soon!
Thanks for visiting Paul.

3. Paul - July 13, 2009

Here is an article debunking the study:

Here is a more full article of the study:

The study also says lesbians are less likely to be non-right handed than heterosexual women when that is not the case. Lesbians are 91% more likely to be non-right handed.

As I said before I think this study is propoganda. There is no way gay people have less brain volume than heterosexuals.

4. Degree Psychology - July 15, 2009

Hey, great post, very well written. You should blog more about this. I’ll definitely be subscribing.

5. Brendan Simons - June 7, 2012

Reblogged this on Self-Esteem, Who Needs It? and commented:
A photo of a gay brain

6. William - June 7, 2012

Reblogged this on Rants Ravings and Revelations and commented:
Mr. Wizard has Nothing on this one

7. Mezm - June 7, 2012

They didn’t consider bisexuals in this study. Or tops, bottoms versatile guys. Another difference to consider would be transgender men and women

8. Reneé Donovan Walter Brewster - October 6, 2012

More Brainmass does not make one more intelligent…
I think it’s brain and boddymass that counts…
Otherwise Wales would outsmarth Homo sapiens…
By the way, I also recale reading about the neocortex, the neocortex is the one that makes a species become intelligent like Homosapiens.

Acording to science Homo Neanderthalensis had bigger cranial capacity compaired to Homo Sapiens, that did not make them more intelligent …
and if it did,
how it is than that our ancestors managed to gradually eliminate them?

So, history shows us that the once with the bigger brainmass gets wiped out by those with the smaller one.

Metaphor: If your aunts computer is bigger than yours, is it correct when she automaticaly asumes that her computer is faster and has more memory and also has more of those ‘superior capacities’?

Biopsych. tells me that Gays have more connections in the corpus callosum, a significantly larger nucleus supra chiasmaticus and also something with the amygdala. So that leads my to belief that Gays have some what more emotional capacities… but what do I know right?
All I can ascertain is that in modern technologie improved artefacts don’t occupy as much unnecessary space as older models.

I don’t know what to belief anymore, if this test shows that HeM has more brainmass, actually I am not that surprised.

My English is bad, but I hope my point got through.

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