Researchers analysed the height to width ratio of 456 male and female participants in romantic relationships. They found that those with a higher face width to face height ratio (FWHDR) reported more randiness than those with a lower ratio.
The study also revealed that men with rounder faces also tended to be more up for casual sex and would be more likely to consider being unfaithful to their partners.
Researchers say that their findings add to growing body of research that shows some psychological and behavioural traits can be determined by face shape. Previously, men with a high FWHR were found to be perceived as more aggressive, dominant, unethical and attractive.
It’s believed that this is due to fluctuations in hormone levels during developmental periods like puberty. These hormones can affect the shape of one’s face and their sex drive.
However if your BF is rocking a moonface it doesn't necessarily mean he's destined to stray, the results show a relationship between the two factors not a cause and effect.