A reader writes, "Men who watch porn featuring two men and a woman produce better-quality sperm, according to this story from New Scientist. The finding suggests that humans may be capable of subconsciously increasing semen quality when faced with the possibility that their sperm will have to outrun those of other men."
The volunteers had previously abstained from sexual activity for two to six days. In samples from men who viewed the images containing the two men and a woman – the "sperm-competition" images – 52% of the sperm were motile. This compared with 49% sperm motility in the men who viewed the images of women only – a difference that was statistically significant after taking into account lifestyle factors such as cigarette smoking and alcohol consumption…
"It's a fascinating study. The effect is obviously immediate. This suggests that something [in the body] can be adjusted very, very quickly," says Jon Evans of the University of New South Wales in Sydney, who studies sperm competition in guppy fish.
