Many people claim to have memories of past lives, explaining them as reincarnation or reverse telepathy or possibly, genetic inheritance.
Dr Rupert Sheldrake , a biochemist from Cambridge, has a new theory which he calls 'morphic resonance', developed from work on patterns of behaviour in rats.
Memory, he suggests, is not stored within the brain: an influence may operate across time and space.
Three personal past-life memories, from Catherine aged 7, John in his 40s, and Winifred in her 80s, may be explained by morphic resonance. Psychiatrist Dr Ian Stevenson of the Division of Parapsychology at the University of Virginia, also comments.
Presenter June Knox-Mawer Producer BARBARA CROWTHER