It’s not unusual to find fellow commuters zoning out on the subway, a sign of diligence and a rite of passage into a hard-working society in Japan.
What’s bizarre, however, is how they know when it’s time to wake up.
The idea that a person loses consciousness inside a moving vehicle and somehow manages to get back to their senses when it’s time to drop off is pretty amazing, and that’s without the aid of conventional alarms, be it smartphones or wearables.
While there has been no research specifically explaining this observation, two doctors offered insights that may as well be considered for future studies.
One possible reason is routine. Speaking to Science of Us, Dr. Marc I. Leavey, a primary-care specialist in Maryland, suggested that the commuter’s body could be used to waking up at a certain time every ride.
“Your body is able to learn a routine as long as it’s a routine,” Dr. Leavey said.
The force at work could be the body’s internal clock, also known as a circadian rhythm. However, such rhythms are built on a 24-hour cycle, making their role on subway naps still questionable.
Another likely explanation stems from the fact that the brain remains at work even while we sleep. This means the commuter could wake up after hearing auditory cues such as the stop announcement or familiar sounds at a particular station.
“The brain does screen out some stimuli during sleep,” Dr. Ronald Chervin, a neurologist and director of Michigan Medicine’s Sleep Disorders Center, told Science of Us.
But he pointed out that the brain can hear some stimuli more than others such as one’s name even when it is spoken at the same volume as other names.
Alternatively, one could not be sleeping until his or her stop. One could wake up at each previous stop and fall back to sleep without any recollection.
“You have to be awake for a certain amount of time to remember,” Dr. Chervin said.
Because the commuter does not recall waking up at previous stations, he or she then assumes sleeping all the way until his or her actual stop.
If anything, these assumptions bring us back to Japan, where napping in public means that a person could be working to exhaustion.
The word is inemuri, often translated as “sleeping on duty,” but some argue to be better off as “sleeping while present,” according to the New York Times. It ties loosely to one staying “present” even at a temporary pause of consciousness, and eventually being able to wake up precisely as necessary.
There’s clearly a need to explore this interesting phenomenon further, but for now, waking up at one’s stop seems like nature’s work. Still, if a routine is behind it all, every practice is worth a shot.