PEOPLE who report encounters with aliens or UFOs are no more mentally disordered or less intelligent than the rest of the population, say scientists at Carleton University, Ottawa. After psychologically testing 'believers' and 'non-believers', they say in Abnormal Psychology that there is no evidence that the former are psychologically disturbed. Between 10 and 15 per cent of people experience a 'malevolent presence' - which some interpret as an alien - because of fluctuating sleep patterns, they add.