Barry knew Alice was tired, but he was surprised that the argument between their three-year-old twin boys did not awaken her. She had not been asleep very long and occasionally changed her position, but did not wake. Alice is probably in:

A. stage 2 sleep.
B. stage 3 sleep.
C. stage 4 sleep.
D. REM sleep.

stage 4

Right.

stage 4

To determine Alice's sleep stage, we need to consider her behavior and level of arousal. In this scenario, Alice is described as being tired and not waking up despite an argument between their twin boys. This suggests that Alice is in a deep stage of sleep.

There are four stages of sleep: stages 1, 2, 3, and REM (rapid eye movement) sleep. Stages 1 and 2 are considered light sleep stages, while stages 3 and 4 are deep sleep stages. REM sleep is associated with dreaming.

Given that Alice is not easily awakened by external stimuli and appears to be in a deep sleep, we can conclude that she is likely in stage 4 sleep. Stage 4 sleep is also known as slow-wave sleep (SWS) and is characterized by slower brain waves and deep relaxation.