Multiple choice

A loud noise awakens you. You emerge from the sleep confused and do not remember the noise. You were in which stage of sleep?

  1. Stage 1

  2. Stage 2

  3. Stage 3

  4. Stage 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stage 4 (deep sleep/slow-wave sleep) has the highest arousal threshold. Waking from it causes sleep inertia - confusion, grogginess, disorientation. Stage 1 is light sleep (easy to awaken, aware). Stage 2 has sleep spindles but moderate arousal threshold. Stage 3 is also deep sleep but Stage 4 is the deepest, hence maximal confusion upon abrupt awakening.

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