The human nose can sniff out gender from body secretions even though people don't think they smell anything, Chinese researchers reported Thursday.

Wen Zhou of the Chinese Academy of Sciences and her colleagues found that two compounds in human bodily fluids, androstadienone in males and estratetraenol in females, effectively signal masculinity and femininity, respectively, in manners contingent upon the recipients' gender and sexual orientation.

"Our findings provide behavior support for human chemosensory communication of gender, and argue for the existence of human sex pheromones," Zhou wrote in an email interview with Xinhua.

Earlier studies showed that androstadienone, found in male semen and armpits, can promote positive mood in females as opposed to males. Estratetraenol, first identified in female urine, has similar effects on males. But it wasn't clear whether those chemicals were truly acting as sexual cues.

In the new study, Zhou and her colleagues recruited participants of different gender and sexual orientation and examined their gender judgments of computer dots that represent a person walking, known as point-light walkers.

Each participant repetitively viewed seven point-light walkers that ranged from slightly more like a male to slightly more like a female, and pressed one of two buttons to indicate whether each was a male walker or a female walker.