Asleep but not dreaming.
Awake and alert.
In Stage 2 sleep.
resemble those obtained during sleep.
Resemble those obtained when a person is awake.
Slow almost to a stop.
show clearly identifiable "trance waves."
Stage 1 NREM sleep.
Stage 2 REM sleep.
Stage 3 NREM sleep.
Stage 4 NREM sleep.
Solving daytime problems
Telling oneself what's missing in one's life.
Categorizing one's experience.
Eye movements accompanying REM sleep.
Emotional catharsis during REM sleep.
The time of peak activity is invariant from person to person.
They are tied to external time markers like light and dark.
They have adapted to technological improvements made in the last century.
Everyone needs at least 8 hours of sleep every night.