Fertile females increase male testosterone levels
Scientists have found that the male arousal hormone, testosterone, peaks in line with a woman's fertility.
Writing in the journal Psychological Science, Florida State University researchers Saul Miller and Jon Maner recruited 37 male students aged 18-23 and four non-pill-using females aged 18-19.
The men, who did not know the purpose of the study, were asked to sniff T-shirts that had been worn by the women for three nights at points straddling ovulation on days 13-15 midway through their cycles, when fertility peaks.
The group were also asked to smell a second set of T shirts worn by the same women, also for three nights, but this time towards the ends of their cycles (days 20-22). A set of unworn T-shirts were also included as a control, and the females were asked to use only neutral-smelling soaps and to avoid wearing perfumes or consuming foods with strong odours during the study.
Before and after the men smelled the shirts, saliva samples were collected to determine testosterone levels. They were also asked how "pleasant" they found the shirt odour in each case.
The analysis showed that the men rated the smells of the shirts worn around the time of ovulation as more pleasant, and the average testosterone level was also significantly higher compared with when they smelled control shirts or shirts worn by the women towards the ends of their cycles.
This suggests, say the researchers, that some sort of smell "cue" is produced by women to broadcast their fertility and that this has the effect of raising male testosterone levels, which is linked to libido and arousal...