It seems some German researchers have uncovered some interesting new evidence on why we routinely wake up a few minutes before the alarm goes off.
Psychology Today: Jan Born and fellow researchers at the University of Lubeck in Germany have discovered what may be the first biological evidence for the curious ability to wake up at will. Anticipating the time you want to rise seems to trigger the release of hormones normally secreted by the body in times of stress. About an hour before you’ve planned to get out of bed, these secretions increase in preparation for the “stress” of waking.