If you want an insight into somebody's true personality, then try to catch a glimpse of the way they sleep.
Scientists believe the position in which a person goes to sleep provides an important clue about the kind of person they are.
Professor Chris Idzikowski, director of the Sleep Assessment and Advisory Service, has analysed six common sleeping positions - and found that each is linked to a particular personality type.
"We are all aware of our body language when we are awake but this is the first time we have been able to see what our subconscious posture says about us.
"What's interesting is that the profile behind the posture is often very different from what we would expect."
To see the six positions studied by Professor Idzikowski
This is the most common sleeping position, adopted by 41% of the 1,000 people who took part in the survey. More than twice as many women as men tend to adopt this position.
arms pinned to your sides. People who sleep in this position are generally quiet and reserved. They don't like a fuss, but set themselves and others high standards.
The remainder of those in the poll said the position they fell asleep varied or did not know.
Professor Idzikowski also examined the effect of various sleeping positions on health.
He concluded that the freefall position was good for digestion, while the starfish and soldier positions were more likely to lead to snoring and a bad night's sleep.
Professor Idzikowski said: "Lying down flat means that stomach contents can more readily be worked back up into the mouth, while those who lie on their back may end up snoring and breathing less well during the night.
"Both these postures may not necessarily awaken the sleeper but could cause a less refreshing night's sleep."
The research also found that most people are unlikely to change their sleeping position. Just 5% said they sleep in a different position every night.
Professor Idzikowski also found that one arm or leg sticking out of the duvet is Britain's most common position, followed by both feet poking out the end.
One in ten people like to cover themselves entirely with the duvet.