It's OK to have coffee with an ex, but sharing a meal with an old flame is a good way to make your current romantic partner jealous, according to a study published this week in the journal PLoS One.
"Meals elicit more jealousy than face-to-face interactions that do not involve eating, such as having coffee," according to Kevin Kniffin and Brian Wansink, from Cornell University in New York, who led this study.
The researchers conducted two experiments to test whether commensality - the technical term for having a meal with someone - with a person other than a current romantic partner triggers feelings of jealousy.
In the first experiment, 79 students from a private university were asked to rate how jealous they would feel if their boy- or girlfriend was "contacted by his/her ex-romantic partner and spent approximately one hour either corresponding by email, talking on the phone, meeting for coffee, meeting for lunch, or meeting for dinner". In the second experiment, 75 students were asked to estimate how jealous their best friend would feel if his or her girl- or boyfriend did any of the activities outlined above.
Their results suggest that sharing a meal was the best way to make a partner jealous, eliciting "significantly more jealousy than coffees," or a long phone chat, the study says. Swapping emails was the least likely way to spark a jealous rage, and there was no difference in feelings of jealousy among men or women, the study found.
The researchers note that conducting the same experiments in different countries or among different groups from students could yield altogether different results. They also recommend that new studies look at whether jealousy is triggered by a romantic partner having a meal with someone other than an ex, especially if the meal partner has the potential to become a love interest.