People with a condition known as rapid eye movement (REM) sleep behavior disorder react physically to the situations they dream, vocalizing, screaming or engaging in sometimes violent motor behaviors while in the REM stage of sleep. This “dream enacting behavior” typically reflects the content of nightmares—often action-filled or violent dreams in which the person is being attacked or is trying to escape danger.
For more on symptoms, causes, and treatment, see Rapid Eye Movement Sleep Behavior Disorder.