-Men facing images of sexual competition may be more fertile.:
Pictures of men with women drive male viewers to produce better-swimming sperm.
It might sound unlikely, but men looking at explicit pictures of two naked men with a naked woman have been shown to produce higher-quality sperm than those watching pornographic images featuring women only.
Although this seems to go against common perceptions about male sexual preferences, it is consistent with the theory of sperm competition, says study leader Leigh Simmons of the University of Western Australia, Perth. This states that males (of many species, including humans) should produce better sperm when faced with a female who has other mates, because this stimulates them to boost their chance of procreation.
The findings may help fertility clinics to obtain the best possible sperm samples from their clients, by providing specialized images of intercourse for men to view. This might help prospective fathers maximize their fertility, Simmons suggests. Though he adds that some women may disapprove of their partner viewing such material.
The report, published online by Biology Letters1, also suggests that men who keep their mobile telephone near to their testes may be harming the quality of their sperm. Before viewing the explicit photos, volunteers in the study were asked to complete a lifestyle questionnaire including details of their alcohol intake, smoking and telephone use. Those who kept a phone in a pocket or clipped to their belt seemed to show lower levels of sperm motility, the researchers note. But experts caution that it is hard to interpret this information, because the study was not designed to look at this effect."