Much like a long-distance romance, it can be difficult to keep the spark alive in a friendship with someone living in a different city. Now scientists say they have uncovered the key to staying close – and it appears to be different for men and women.

Men need to meet up face-to-face and bond over activities, according to the study of students leaving home for the first time, while for female friendships, long phone conversations can bridge the physical distance.

Professor Robin Dunbar, who led the work at the University of Oxford, said: “What determined whether [friendships] survived with girls was whether they made effort to talk more to each other on the phone.”

However, talking had absolutely no effect on boys’ relationships, the study found. “What held up their friendships was doing stuff together,” said Dunbar. “Going to a football match, going to the pub for a drink, playing five-a-side. They had to make the effort. It was a very striking sex difference.”

In the research, thirty students who were in their final year of sixth form were asked to compile detailed lists of all their friends and how close they felt to each of them.

Four months after the initial assessment, the students took their final A-level exams and many left home for university. They were then followed up nine months and 18 months after the initial assessment.

Speaking to journalists on Saturday at the annual meeting of the American Association for the Advancement of Science in Boston, Dunbar said different friendship styles between genders could be behind the effect.

“This is about the idea that women clearly have much more intense close friendships,” he said. “They’re very intense, very like romantic relationships – in the sense if they break, they break catastrophically.”

By contrast, men tend to have more casual friendships.

“They tend to have a group of four guys that they do stuff with,” he said. “With guys it is out of sight out of mind. They just find four more guys to go drinking with.”