Researchers at the Chinese Academy of Sciences have released the latest research suggesting that sexuality is hardwired in the human brain by showing that gay men and women react to male sex pheromones while heterosexual men ignore them.
The scientists set up an experiment in which they exposed men and women to the pheromones androstadienone (found in male sweat and semen) and estratetraenol (found in female urine).
They then showed them a video animation of a person walking made up of dots marking the various joints of the body and asked to guess it was a man walking or a woman.
Heterosexual women and gay men who had been exposed to androstadienone were more likely to guess that the figure was a man, while exposure to the hormone had no effect on how heterosexual men guessed about the figure.
Heterosexual men who were exposed to estratetraenol were more likely to guess the walking figure to be female while heterosexual women were not affected by exposure to the hormone.
Bisexual and lesbian women were also more likely to guess the figure was a woman but the results were not as pronounced as for the gay men in the study.
The researchers, Wen Zhou, Xiaoying Yang, Kepu Chen, Peng Cai, Sheng He and Yi Jiang, published their results in the journal Cell yesterday.
‘Homosexual males exhibit a response pattern akin to that of heterosexual females, whereas bisexual or homosexual females fall in between heterosexual males and females,’ the researchers wrote in a summary of their findings.
‘These effects are obtained despite that the olfactory stimuli are not explicitly discriminable. The results provide the first direct evidence that the two human steroids communicate opposite gender information that is differentially effective to the two sex groups based on their sexual orientation.
‘Moreover, they demonstrate that human visual gender perception draws on subconscious chemosensory biological cues, an effect that has been hitherto unsuspected.’
Previous research by Sweden’s Karolinska Institute had shown that the hypothalamus region of the brain lights up in gay men and lesbians when they are exposed to sex pheromones of their same sex.