Date Published: May 22, 2013
Publisher: Public Library of Science
Author(s): Paavo Huoviala, Markus J. Rantala, Angela Sirigu. http://doi.org/10.1371/journal.pone.0062499
Androstadienone, a component of male sweat, has been suggested to function as a human pheromone, an airborne chemical signal causing specific responses in conspecifics. In earlier studies androstadienone has been reported to increase attraction, affect subjects’ mood, cortisol levels and activate brain areas linked to social cognition, among other effects. However, the existing psychological evidence is still relatively scarce, especially regarding androstadienone’s effects on male behaviour. The purpose of this study was to look for possible behavioural effects in male subjects by combining two previously distinct branches of research: human pheromone research and behavioural game theory of experimental economics. Forty male subjects participated in a mixed-model, double-blind, placebo-controlled experiment. The participants were exposed to either androstadienone or a control stimulus, and participated in ultimatum and dictator games, decision making tasks commonly used to measure cooperation and generosity quantitatively. Furthermore, we measured participants’ salivary cortisol and testosterone levels during the experiment. Salivary testosterone levels were found to positively correlate with cooperative behaviour. After controlling for the effects of participants’ baseline testosterone levels, androstadienone was found to increase cooperative behaviour in the decision making tasks. To our knowledge, this is the first study to show that androstadienone directly affects behaviour in human males.
Pheromones are known to influence behavior in numerous animal species, but it has for long been thought that they are not important for human behavior and social interaction. However, in recent years, research on human pheromones has revealed various interesting psychological and physiological phenomena. Perhaps the most widely studied of the putative human pheromones is the compound androstadienone (4, 16-androstadien-3-one), found in relatively large quantities in male axillary sweat , . Androstadienone has been reported to modulate women’s attributions of male attractiveness , have, in some cases sex and context dependent, effects on mood (for example, , ), and direct attention towards emotional information . Furthermore, androstadienone has been shown to maintain increased levels of salivary cortisol in women , activate hypothalamus in a sex  and sexual orientation dependent manner , , and activate brain areas related to social cognition and attention . However, psychological evidence outside the, often context dependent, mood enhancing qualities remains scarce. This is especially true for male responses to androstadienone.
The purpose of this study was to find out if the putative male pheromone, androstadienone, carries information relevant for social decision making, as measured by behaviour in ultimatum and dictator games. Furthermore, we wanted to find out whether androstadienone affects male salivary hormone levels (cortisol and testosterone), as seen in females . Our first hypothesis was that male participants exposed to androstadienone behave more co-operatively in the ultimatum and dictator games. This hypothesis received support: when controlling for participant baseline testosterone levels, the androstadienone receiving group accepted significantly lower offers as Responders, and the difference between Proposer offers and the minimum acceptable offers was significantly higher than in the control group (meaning that participants offered more and asked for less). There was also a tendency in the androstadienone receiving group to make larger offers as Proposers and as sole decision makers in ultimatum. Thus, it seems that androstadienone increased cooperation in ultimatum and dictator.