While it may seem obvious that falling asleep in front of the telly may not be the most restful environment, a new study has revealed a specific reason why.
Researchers measured the brain activity of sleeping adults in response to familiar and unfamiliar voices while sleeping. They found that the brain pays attention to unfamiliar voices during non-rapid eye movement (NREM) sleep to stay alert to potential threats.
During this first stage of sleep, the brain is on high alert, so it doesn’t know whether the voice you’re hearing is a burglar or The Walking Dead star, Norman Reedus.
Even though our eyes are shut, the brain continues to monitor the environment as we sleep, balancing the need to protect sleep with the need to wake up.
It’s thought that this may be evolutionary, dating back to the need to wake quickly in the face of potential danger.
Although the evolutionary behaviour remains, the potential danger has changed dramatically from wild animal, to binge watching.
The research took place in Austria at the University of Salzburg and involved 17 volunteers being fitted with polysomnography equipment during a full night's sleep.
Polysomnography measures things such as brain waves, respiration, muscle tension, movements and heart activity during different sleep stages.
The study found that unfamiliar voices elicited more K-complexes, a type of brain wave linked to sensory disturbances during sleep, compared to familiar voices.
Researchers didn't see the effect during REM, the deepest stage of sleep. So, if you’re deep enough in snooze town, even the sounds of a zombie apocalypse blaring from your screen won’t disturb your rest.