Taking flowery perfumes and dirty gym socks out of the picture, is it possible to distinguish a man from a woman using nothing other than your nose? According to a new study released online in the May issue of Current Biology, it is. Researchers have found that the human body releases chemical cues to let others know our gender. Our interpretation of these chemicals is influenced by both our biological sex and our sexual orientation.

Even though we are usually completely unaware, humans have the ability to smell gender. Past research has found that androstadienone, a hormone found in male semen and sweat is able to promote a positive mood in females. Estratetraenol, found in female urine, has a similar effect on males. So, researchers set out to explore just how far this ability to sniff out gender went.

In a recent study, they asked males and females who identified as either homosexual, bisexual, or straight, to watch what is known as point-light walkers (PLWs) on a screen. The PLWs were made up of 15 dots representing an outline of a human body. The volunteers were asked whether they thought the figures outlined in the PLWs were more masculine or feminine. The participants’ answers were recorded after their exposure to androstadienone, estratetraenol, and a placebo.

Results from this study clearly show that these two hormones act as sexual cues. Straight women who smelled the male hormone were more inclined to perceive the PLW figure as masculine. Curiously, exposure to the male hormone did not greatly affect gender perception in straight males. Results from exposure to the female hormone yielded similar effects, with straight males, and not females, being more likely to perceive the figure as female. “Smelling androstadienone versus estratetraenol produced about an eight percent change in gender perception,” Wen Zhou, led researcher of the study, explained in a press release.

Things got interesting when researchers repeated the same experiment on participants who identified as homosexual or bisexual. Homosexual males' responses were similar to straight females. Homosexual and bisexual females’ results fell somewhere in the middle of results from the heterosexual males and female. This is the first direct evidence that an individual’s sexual orientation can affect their perception of these two human steroids.

Source: Zhou W, Yang X, Chen K, Cai P, He S, Jiang Y. Chemosensory Communication of Gender through Two Human Steroids in a Sexually Dimorphic Manner. Current Biology. 2014.