UK researchers are asking for your help to find out exactly what is behind out-of-body experiences (OBEs).
Some have OBEs when they have narrowly escaped death
Psychologists at Manchester University have set up an online survey that they hope about 3,000 people will fill out.
By comparing the responses of those who have and have not had an OBE they aim to discover the overarching cause.
One theory is that it is down to how people perceive their own body - those unhappy or less in touch with their body are more likely to have an OBE.
About one in 10 people claim to have had an OBE at some time, typically involving a sensation of floating and seeing the physical body from outside.
For some, the phenomenon occurred spontaneously, while for others it was linked to dangerous circumstances, a near-death experience, a dream-like state or use of alcohol or drugs.
Despite this, relatively little is known about OBE.
Dr David Wilde and his team plan to find out more by studying the experiences of a large number of people.
He said there were several theories as to why people have OBEs.
"There were early theories which looked at whether something actually physically left the body, like consciousness, but there's no real scientific evidence for that.
"Other theories over the years have looked at whether OBE is a psychological defence mechanism in response to a perceived threat to the body in some way.
"Others have wondered whether it is a visual hallucination.
"But what has connected all the theories is the fact that they all start from a feeling of a loss of input from the body - a loss of conductive information coming from the legs, the arms, the trunk and so on.
"Our theory follows on from that."
His team believes that people experience their body in different ways and that this could explain why some people experience OBEs while others do not.
"We are finding that people with OBEs tend to experience their body differently to others.
"They tend to have increased social anxiety, to be uncomfortable about their body being scrutinised by others and dissatisfied with their bodies, and they tend to get immersed and absorbed in things very easily."
He said that by studying more people over the coming months he will be able to check whether his theory is correct.
The anonymous survey, funded by the Bial Foundation, can be accessed at www.freeresponse.org/muobe2005/