Suspected infidelity - and the jealousy that goes with it - can be a major source of relationship tension.
But is there a way we can predict if our partners are likely to cheat on us?
According to a new study by researchers at Harvard University, there is; and it's all to do with perceived attractiveness.
Social psychologist Christine Ma-Kellams and her team conducted a series of experiments that looked at the link between physical beauty and relationship break-ups in heterosexual relationships.
They found that people who were rated as more attractive in their yearbook photos from the 70s and 80s were more likely to be divorced 10 or 20 years further down the line.
They also found that more conventionally attractive people in committed relationships had a higher likelihood of having a "wandering eye".
Participants in this experiment, just under half of whom were in exclusive relationships, were tasked with rating the attractiveness of a "target" of the opposite sex. The team identified that those in committed relationships who were more physically attractive showed more interest in the targets.
So, more physically attractive people are more likely to cheat - it's a conclusion that seems predictable, right?
However, the social psychologists also discovered that this tendency to cheating would be swayed by perceived attractiveness as well as actual attractiveness; and it's something that is exacerbated by relationship dissatisfaction.
To get to this result, researchers first attempted to make a group of volunteers feel more attractive by showing them a series of photos of less attractive, same-sex people.
When these participants were asked to rate images of attractive opposite-sex targets, they were more likely to rate them as attractive, especially if they admitted they were unhappy in their current relationships.
However, the same was not true for the group who were made to feel less attractive prior to being asked to rank the attractiveness of others.
The upshot? When made to feel attractive, people who weren’t satisfied in their relationships became more attracted to extra-relationship alternatives.
And, in the words of the researchers, "being physically attractive is not without its relational liabilities".
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