Women who have affairs can now blame it on their hormones, as a new study suggests those with high estrogen levels not only look and feel more attractive—they’re also more likely to move from man to man. Estrogen, which affects female fertility, has been shown to make women dress more provocatively and take bigger risks, Reuters reports. According to the latest research, which focused on 52 women aged 17 to 30, those with higher levels of estradiol (a type of estrogen) were more likely to flirt, kiss, and have a serious affair with someone other than their primary partner. They reported more sexual behaviour, too, although no more one-night stands than the low-estrogen group. The findings suggest that “women high in reproductive health engage in opportunistic serial monogamy – being open to affairs and moving on to a new relationship if a higher-quality mate becomes available,” said the researchers, based at the University of Texas at Austin.