Study examines couple's closeness at Edinburgh International Science Festival
Closeness between couples is reflected in the distance separating them as they sleep, a study has found.
Partners who sleep less than an inch apart were more likely to be happy with their relationship than those maintaining a gap wider than 30 inches.
Couples making physical contact were happier than those with a "no touching" rule while trying to sleep.
The survey of 1,000 people was conducted as part of the Edinburgh International Science Festival.
The survey also revealed the most popular sleep positions of couples, with 42% lying back to back, 31% facing the same direction and 4% facing one another.
12% of couples spent the night less than an inch apart while just 2% were separated by more than 30in.
Professor Richard Wiseman, University of Hertfordshire psychologist leading the study, said: "One of the most important differences involved touching.
"94% 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.
"This is the first survey to examine couples' sleeping positions, and the results allow people to gain an insight into someone's personality and relationship by simply asking them about their favourite sleeping position."
The study found 86% of couples who slept less than an inch away from each other claimed to be happy with their relationship compared with 66% who slept more than 30in apart.
Out-going extroverts tended to spend the night close to their partners, and more creative individuals were more likely to sleep on their left hand side.
Prof Wiseman is the author of Night School, which examines the science of sleep and dreaming.