Behavioural scientists are currently attempting to correlate individuals' usual duration of sleep with personality traits as well as with personality profiles. Studies using the Minnesota Multiphasic Personality Inventory (MMPI) and Cornell Medical Index have suggested that differences between “short sleepers” and “long sleepers” show up in such traits as self-control, anxiety, extroversion, aggression and ambition (Hartmann et al, 1972; Spinweber & Hartmann, 1976), although Webb & Friel (1970, 1971) found no such differences. Glaubmann & Orbach (1977) observed short sleepers to be efficient, energetic, ambitious, self-content and socially well adjusted.