Sexual preference on the brain, as reported in articles in ScienceNOW 9 May 2005 and BBC Online News, 18 May 2005.
A study of brain responses to exposure to male and female pheromones revealed differences between homosexual and heterosexual men. Pheromones are small scent molecules that act as chemical signals to activate parts of the brain involved in sexual arousal. These have been identified in many animal species but their role in human sexual behaviour is less clear. Scientists at the Centre of Gender-Related Medicine at the Karoliska institute in Stockholm, Sweden tested two molecules named AND, a derivative of the male hormone testosterone, and EST a derivative of the female hormone oestrogen. These are excreted in sweat and urine and previous studies using clothing worn by men and women indicate that male and female odours contribute to sexual arousal.
The researchers looked for activity in the hypothalamus of 12 heterosexual men, 12 homosexual men and 12 heterosexual women as they were exposed to these chemicals and compared it with responses to neutral odours such as lavender. They found that women and homosexual men responded to the AND but not to the EST, and heterosexual men responded to the EST but did not respond to the AND.
Dana Small, a neuroscientist at Yale University urges caution in interpreting the results. He commented that while the study identifies a way sexual preference may be encoded in the brain, homosexual men may become sensitive to AND through having sexual relations with other men, rather than being born with a built-in response to the chemical.
Editorial Comment: Dana Small’s comment is important – just because the brain responds in a certain way does not necessarily mean that the response or behaviour is biologically built-in. Brain activity does change with learning, especially if it starts early in life. This is why God’s people are instructed to teach their children the ways of the Lord, and gave clear instructions about right and wrong sexual relations.
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