Androstadienone [AND] is a human steroid that is present in male semen and sweat. It heightens sympathetic arousal, alters levels of cortisol, and promotes positive mood state in females. Androstadienone is also found to activate the hypothalamus in heterosexual females and homosexual males, but not in heterosexual males or homosexual females.  Estratetraenol [EST] is the female equivalent of this steroid. 

One of the stumbling blocks to finding the role of a pheromone in humans is our lack of a functional vomeronasal organ [VNO] and an accessory olfactory bulb. Without the anatomical ability to detect the scent of a pheromone, it is unclear how a pheromone would affect human behaviour.  

Zhou et al carried out an experiment to see the effect of AND and EST on heterosexual and homosexual men and women. The sample was made up of four groups of healthy non-smokers, including 24 heterosexual males, 24 heterosexual females, 24 homosexual males and 24 bisexual or homosexual females. Participants were presented a point-light walker task (PLW), a set of dots that move in a way which represents the properties of human motion.  The participants were asked to observe the stick figure in motion and to identify its sex.

They performed the task at around the same time of the day on three consecutive days while being continuously exposed to either androstadienone mixed with cloves, estratetraenol mixed with cloves, or a control solution, also mixed with cloves.  The participants only carried out the task while smelling one of the solutions each day.  The scents were counterbalanced to control for order effects.  

The researchers found that when heterosexual females and gay males were exposed to AND, they had a higher rate of identifying the stick figure as “masculine” than the control group.  AND had no significant effect on heterosexual men or lesbian women. By contrast, smelling EST systematically biases heterosexual males toward perceiving the walkers as more feminine. The effect was not statistically significant in bisexual and lesbian women.

It appears that AND and EST may have some effect on human sexual behaviour.

The study is an experiment where the IV was manipulated, allowing the researchers to establish a cause and effect relationship between the IV (the use of AND or EST) and the behaviour (rating of the stick figure). However, the research carried out the experiment with different groups based on gender and sexuality and obtained different findings.  These other variables must also play a role in the strength of the effect of the IV on the DV.

However, the study was counter-balanced to control for order effects, such as the practice effect.

Hare et al (2017) failed to replicate the study.  This means that the results may not be reliable. The researchers found that exposure to the putative pheromones had no significant effect on gender perception or attractiveness.

The dose of AND and EST used in this study was significantly higher than humans naturally secrete. This means that although Zhou's study determined a significant effect, it is unlikely that this represents actual human behaviour.