person can usually  recall a dream.  However,  this ability
declines    rapidly     as    the    awakening     is      delayed.
Consequently,   in  the   morning  the  dreamer  will  have
some    difficulty  in  recalling   the  dreams  he  reported
during  the previous night.  This indicates  that  we  forget
dreams not only after we awaken but also while we sleep.
     People who complain that they never dream have been
invited to sleep  in dream laboratories.  There the dreams
are  extracted  during  the  night  and  in  the  morning the
dreamers are presented  with their recorded reports.  It is
clear,  then,  that when we awaken  in the morning without
a dream it is because we have forgotten.
     Apparently  the mind  never sleeps,  for when sleepers
are awakened  from other than  the dream state,  they will
usually  report   that  something  was   going  on  in  their
minds.   Sometimes   they   will  report   that   they   were
dreaming,   but   not   so  frequently   as  when   they   are
awakened  from  the  dream  state  of sleep.  More  often
they  will  say  that  they  were  "thinking."  This  reported
thinking    activity    resembles     normal    thought    and
typically    relates   directly   to   the   sleeper's   daytime
concerns.
     Why is it,  then, that although  we  have  been mentally
active    throughout    the    night,    we    experience    our
awakening  as  the  emergence  from  unconscious sleep?
Why should  we  be able  occasionally  to  recall some of
our  dreaming  but  typically  none  of  our thinking?  This
discrepancy  is   puzzling,   since   during   the   night   we
spend much  more  time  thinking  than  we  do  dreaming.
Moreover,   the   quality   of   our   nocturnal   thinking  is
perfectly  compatible  with   that  of our  waking  thought,
whereas   the   quality   of   our   dreaming   is   quite   the
contrary.
     When  we  look for  the factor that  favors dreams and
that   affords   them   some   tentative   privilege   to   our
memory,  we find that  it  is  the activation that is present
during  the  dream  stage  of  sleep.  The dream  state  has
been called activated  or paradoxical sleep because of its
resemblance  to  a  waking  state.  It  is,  in some sense, a
partial awakening.  It  is  a psychological principle  that a
certain  degree  of  arousal   is   necessary   if  we  are  to

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