For women who are worried about their spouse cheating on them, a drug may provide the answer, as researchers discovered it reduces the likelihood of straying.
Waseda and Kyushu University professors tested the affects of antibiotic minocycline. They found that with taking the drug, men were less likely to rate attractive women as trustworthy.
The study consisted of 98 men who were split into two groups. One group was given a four-day treatment of minocycline, while the other was given a placebo.
The men were shown pictures of female faces and told to choose how much money they would give to each female.
When they chose to share their money, the amount was tripled.
Then the men were told that the females would get the choice of sharing the money or taking it all.
Men rated them on a trustworthy scale and also rated how physically attractive they were.
The results showed that men rated attractive women as more trustworthy, but this was not true for the men taking minocycline.
Trustworthiness, the researchers believe, is one of the main components of choosing a partner to cheat with.
They also found that the attractiveness of the women increased when the money was involved.
"In movies, a female spy often wins the trust of her male target using her physical attractiveness. The male target usually suspects that she is a spy despite concerns regarding her trustworthiness," the study explains.
"For males, allocating valuable resources to physically attractive females may be evolutionarily adaptive, in that it may increase the probability of producing attractive offspring under natural selection."