Tuesday, 17 June 2008

Scans see 'gay brain differences'

(Ed: This article really needs to be read alongside a primer in 'How to do scientific research and test hypotheses.' The observational data are straightforward: "The brains of gay men and women look like those found in straight people of the opposite sex." The 'conclusion' of the quoted UK scientist, that this is evidence that sexual preference is set in the womb, is a gazillion miles from that data - even if it is true. The first obvious question: how many, if any, straight men and women also have brains that show the same resemblances to those of straight people of the opposite sex? The second question: are there gay men and women who do not have this brain similarity to straight people of the opposite sex? There are probably other questions that might occur to you.)

The brains of gay men and women look like those found in straight people of the opposite sex, research suggests.

The Swedish study, published in the Proceedings of the National Academy of Sciences journal, compared the size of the brain's halves in 90 adults.

Gay men and straight women had halves of a similar size, while the right side was bigger in lesbian women and straight men.

A UK scientist said this was evidence sexual preference was set in the womb.

Scientists have noticed for some time that homosexual people of both sexes have differences in certain cognitive abilities, suggesting there may be subtle differences in their brain structure.

This is the first time, however, that scientists have used brain scanners to try to look for the source of those differences.

A group of 90 healthy gay and straight adults, men and women, were scanned by the Karolinska Institute scientists to measure the volume of both sides, or hemispheres, of their brain.

When these results were collected, it was found that lesbian women and straight men shared a particular "asymmetry" in their hemisphere size, while straight women and gay men had no difference between the size of the different halves of their brain.

In other words, structurally, at least, gay men were more like straight women, and gay women more like straight men.

A further experiment found that in one particular area of the brain, the amygdala, there were other significant differences.

In heterosexual men and lesbian women, there were more nerve "connections" in the right side of the amygdala, compared with the left.

The reverse, with more neural connections in the left amygdala, was the case in homosexual men and straight women.

The Karolinska team said that these differences could not be mainly explained by "learned" effects, but needed another mechanism to set them, either before or after birth. Read more

No comments will be posted without a full name and location, see the policy.

1 comment:

Jonathan Mobey said...

Association does not entail causation. Even if there are statistically-significant structural differences between the brains of 'gays' and 'non-gays', it must be asked whether the brain difference causes 'gayness', or whether 'gayness' causes the brain difference.

Whilst the study authors believe that these differences could not be mainly explained by "learned" effects, it must be recognised that often structure is a result of function, and not the other way round, e.g. doing regular press-ups gives me a well-toned torso - and not the other way round. In itself this study does not prove causation.