 Since 1964 he has collaborated with Celia Green on a series of studies of hallucinatory experiences in ostensibly normal people, including studies of out-of-body experiences, in which people seem to perceive their own physical body ‘from outside’.From 1987 to 2000 he also collaborated with the Oxford psychologist Gordon Claridge on work on the theoretical construct of schizotypy.In 1993 he was awarded a doctorate by the University of Oxford for work relating out-of-body experiences to schizotypy.