Bad breath points to sex

People can correctly guess the sex of a fellow human simply by smelling their breath, according to a blind study carried out in 1982 at the University of Pennsylvania in the US.

In their experiments, 19 female and 14 male college students acted as odour donors (they refrained from cleaning their teeth or eating garlic and heavily spiced foods for the five days of the study). Then ten odour judges were recruited from the university campus five male and five female.

Odour donors and judges were separated by a screen in a large, well ventilated room. Each donor exhaled into a glass tube which was then passed through the screen.

On the opposite side, the judges inhaled the breath of the donor and ranked it on a seven-point scale according to its intensity and pleasantness or otherwise. In addition, each judge was asked to guess the sex of the donor.

Both male and female judges correctly guessed the sex of the donors in 95% of cases. Female judges were better at identifying males and male judges slightly better at identifying females, circumstantial evidence for this unconscious ability points to hormonal differences and a whole lot of evolution.