Watch the eyes for this sign that a partner is 50% more likely to cheat on you.

Partners who spend a fraction of a second longer looking at other people they find attractive are 50% more likely to cheat, psychological research finds.

The marriages of those who can’t keep their eyes in their heads are also more likely to fail.

Other signs of infidelity were hidden in couple’s appearance and dating history.

Less attractive women were more likely to be unfaithful, it emerged.

Among men, those that reported more short-term sexual partners before marriage were more likely to have an affair.

The opposite was true for women: the more sex partners before marriage, the more faithful women were during marriage.

The conclusions come from a study in which newlyweds were shown pictures of both average-looking and very attractive men and women.

Those that had trouble looking away from the very attractive pictures were 50% more likely to cheat.

Professor Jim McNulty, the study’s first author, said:

“People are not necessarily aware of what they’re doing or why they’re doing it.

These processes are largely spontaneous and effortless, and they may be somewhat shaped by biology and/or early childhood experiences.”

Faithful newlyweds were more likely to downgrade or discount the very attractive faces they saw.

This helped them put these other options out of their mind.

The study followed 233 newlyweds for up to the first 3.5 years of their marriage.

Professor McNulty said that social media has a role to play in the US divorce rate, which is approaching 50%:

“With the advent of social media, and thus the increased availability of and access to alternative partners, understanding how people avoid the temptation posed by alternative partners may be more relevant than ever to understanding relationships.”

The study was published in the Journal of Personality and Social Psychology (McNulty et al., 2018).