A new study suggests couples' sleeping positions reveal how healthy their relationship is.
Partners who slept less than an inch apart were more likely to be happy with their relationship than those maintaining a gap wider than 30 inches.
In addition, more couples who spent the night making physical contact were happy than those with a "no touching" rule while trying to sleep.
The survey of 1,000 people, conducted as part of the Edinburgh International Science Festival, 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.
Twelve per cent of couples spent the night less than an inch apart while just 2% were separated by more than 30 inches.
– University of Hertfordshire psychologist Professor Richard Wiseman
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.
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 that 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 30 inches apart.
Out-going extroverts tended to spent 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.