Final answer:
Yes, an observer can see the eyes darting back and forth under closed eyelids during REM sleep.
Step-by-step explanation:
Yes, an observer can see the eyes darting back and forth under closed eyelids during REM sleep.
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REM sleep, or rapid eye movement sleep, is a stage of sleep characterized by rapid movements of the eyes. These eye movements can be observed by an outside observer even with closed eyelids. This is because during REM sleep, the brain waves associated with wakefulness are present, and the eyes move in a way that mimics the movements when the person is awake.
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For example, if you were to observe someone in REM sleep, you might see the eyes moving rapidly from side to side or up and down.