METHODS
Using an experimental design we photographed the
faces of 23 adults (mean age 23, range 18-31 years, 11
women) between 14.00 and 15.00 under two conditions
in a balanced design: after a normal night’s sleep (at
least eight hours of sleep between 23.00-07.00 and
seven hours of wakefulness) and after sleep deprivation
(sleep 02.00-07.00 and 31 hours of wakefulness). We
advertised for participants at four universities in the
Stockholm area. Twenty of 44 potentially eligible people
were excluded.