It is often said the secret to a long and happy marriage or relationship is to have separate beds so each partner can get a good night's sleep.

But now a survey of 1000 people conducted for the Edinburgh International Science Festival has revealed the opposite appears to be true.

Research found couples who slept less than an inch apart were more likely to be happy with their relationship than those maintaining a gap wider than 30in. In addition, more couples who spent the night making physical contact were happier than those with a "no touching" rule while trying to sleep. The study also revealed that 42% of partners lie back to back, 31% face the same direction, but only 4% face one another. Twelve per cent spent the night less than one inch apart while just 2% were separated by more than 30 inches.

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Steven Camley's cartoon 

Study author Professor Richard Wiseman of the University of Hertfordshire said: "One of the most important differences involved touching. Ninety four per cent of couples who spent the night in contact with one another were happy with their relationship, compared to just 68% of those that didn't touch."