Temperature has long been known to affect sperm production, and Popular Science reports that a new study published in the Scottish Medical Journal reviewed evidence of the link between scrotal temperature and reproduction.
Author Erwin J.O. Kompanje decided to study the veracity of anecdotal reports that kilt-wearing men have better sperm quality and better fertility.
The study, titled "Real men wear kilts," says wearing a kilt "likely produces an ideal physiological scrotal environment, which in turn helps maintain normal scrotal temperature, which is known to be beneficial for robust spermatogenesis and good sperm quality."
Kompanje reviewed other research on kilt-wearing Scots and found that 70 percent choose to go undergarment-free in the "regimental" style. Kompanje writes that a downturn in Scottish fertility is correlated with the frequency of kilts being worn, although he admits it's still speculative until a randomized trial happens.
Wearing kilts might also be psychologically valuable in countries like Scotland where there is less stigma surrounding men wearing the skirt-like garment. Men who wear kilts experience increased feelings of freedom and masculinity, and see positive engagement with women. Research also suggests the kilt "gives a man a sensuous awareness of his own body and how it will be seen by others."