It is a type of behaviour the correct term is REM behaviour disorder, people who had this kind of disorder act out their dreams. Some move their limbs or even shouting, screaming, hitting or punching. This also used as a defense of committing murders while sleep walking.
Answer:
When you are dreaming you are in REM sleep, and when in REM sleep you lose muscle tone which puts you in an almost paralyzed state.
Explanation:
Plato, it explains it in unit 8 lesson 3.
