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Perhaps you’ve seen them, those mysterious people who can fall asleep on the bus or the train and then, somehow, rouse themselves exactly at their stop. Perhaps you’re one of them. It’s as if the subway napper’s brain can sense exactly where and when it is in time and space, rousing the sleeper so she can exit at the right time.

How is this possible? While there’s little research about this apparent superpower, a few doctors were game to offer their insights about it. Science of Us spoke to Dr. Marc I. Leavey, a primary-care specialist based in Lutherville, Maryland, and Dr. Ronald Chervin, a neurologist and director of Michigan Medicine’s Sleep Disorders Center, to hear possible reasons why some people are able to wake up at exactly the right stop:

Because your body’s internal clock is synced up to that particular stop.

When you set an alarm, your body becomes primed to wake up at a certain time each day. The same thing might be happening here: It’s possible that your body gets used to waking up at a certain point each time during your commute, Leavey explained. That holds especially true if you commute at the same time every day, so that your body’s internal clock becomes used to timing a wake-up at the same point each morning.

“Your body is able to learn a routine as long as it’s a routine,” Leavey said. This suggests that if you were to get on at a different time, or if the journey was delayed, your internal clock wouldn’t wake you up at your stop.

It’s an intriguing theory, but Chervin doesn’t fully buy it. Circadian rhythms can help explain why you might wake up at the same time every morning, but he’s skeptical that they can also explain why you wake up after a brief nap.

Because you’re still hearing the announcements of the stops, even while you sleep.

It’s also possible that you’re able to wake up for your particular stop due to an oral cue, like the conductor stating the name of the subway stop over the PA system, or a musician at that station playing the saxophone. Such cues alert your brain that you’ve arrived, Leavey said. Just as with the motion of the train, in this case it’s the external forces, rather than internal cues, that make you wake up.

“The brain does screen out some stimuli during sleep,” Dr. Chervin noted. But your brain is actually primed to hear some stimuli more than others. For example, Dr. Chervin said, some research shows that you’re more likely to hear your name than any other name while you sleep — even if the words are spoken at the same volume. For example, a 2013 study published in the Public Library of Science found that, during sleep, our brain reacts differently when hearing our own name versus other people’s names. The results indicate that our brain may inhibit certain sound processing during sleep, but is still attuned to others.

So this suggests that your brain doesn’t turn off during sleep — it just screens for certain stimuli, Chervin explained. That means that it may be able to pick up on the announcement of your stop.

Because you’re actually waking up more than you think you are.

Another intriguing possibility: You may not be sleeping until exactly your stop — in fact, Chervin said, you may wake up at each stop, check if it’s yours, and go back to sleep, all without remembering it. “You have to be awake for a certain amount of time to remember,” he explained.

Chervin says that he sees this all the time in cases where patients are suffering from sleep apnea. Patients may come in chronically sleep-deprived and unsure of why they feel so sleepy all the time. But they may be waking up as many as 200 times in the night, even if they don’t remember a single instance. Instead, they’re falling right back asleep, before their brain has time to process their experience into long-term memory, he said.

Similarly, you could be waking up every time the subway or train comes to a stop, or every time you hear a new stop called. But you just don’t remember it until you stay awake at your stop — leading you to believe that you’ve slept the whole way through and miraculously woken up at the right time.

Still, not everybody can manage the subway nap without missing their stop …

If you can’t pull off this commuter trick, your body may not yet be primed to wake up at that particular time, or you may be sleeping too deeply to respond to oral cues.

“Sleep is a very interesting thing,” Leavey explained. “If you’re in REM sleep, it’s much harder to wake you up.” REM (rapid eye movement) sleep is essentially a deeper stage of sleep when you’re dreaming, and you enter this stage after about 20 minutes of snoozing, Leavey said. “If you’re in a deep REM sleep, you’re liable to miss your stop or sleep through it,” he added. You’re more likely to be tired or disoriented when you wake up from these dreams, so if you’re sleeping for longer than 20 minutes, you may find it harder to wake up out of this dream state. (That’s why a power nap, Leavey said, is typically considered about 18 minutes.)

You also may have trouble waking up if you don’t get enough sleep. “Many, and probably most of us, walk around in a sleep-deprived state,” Chervin said. “Those of us who are more sleep-deprived than others will be more likely to go into deeper stages of sleep faster … and may have more trouble waking up at a designated or specific time.”

… but you can teach yourself.

If you tend to snooze through your stop, though, don’t despair: You may actually be able to train yourself to wake up at your appointed destination. In order to do so, you have to get into a routine, so your body can start responding to the pattern, Leavey said. Make a conscious effort to get on the train at the same time each day, since your body is more likely to wake you up at a specific time each day, like 7:30 a.m., rather than after a specific amount of travel time, such as 15 minutes.

If you want, you can even set your phone alarm for about three minutes before your stop, until your body gets used to waking up at the same time, Leavey said. Once you do this repetitively for a certain amount of time, your body will start to naturally wake you up at this point. We all have an internal clock. By commuting at the same time every day, your master internal clock will kick in and help you wake up at the specified time.

Ultimately, though, napping on your commute may not be a great thing, whether or not you can train yourself to wake up at the right stop.

“If you’re falling asleep the minute you’re sitting down for 20 minutes, there’s probably something wrong with your sleep health,” Chervin said. Try spending more time in your actual bed — a change we can all get on board with.