If you followed the Olympics last year, you might've noticed Boomer Phelps sleeping through the Today show. This probably didn't surprise you if you've spent time around an infant. Babies seem to have an uncanny ability to stay asleep even amid chaos. According to an article in The Guardian by Dr. Daniel Glaser, director of Science Gallery at King’s College London, that's because their brains are actually wired differently.
Since babies rely on adults to watch out for them while they're getting Zs, their brains don't need to detect noise in their sleep. That's what the grown-ups are for. "Human babies are among the most adult-dependent of all animal species, which is what allows them to develop," Glaser explains. "This means they don’t have to be alert to different noises while they sleep."
Unfortunately for us, this ability to filter out loud music, alarm clocks, and pretty much every other sound fades by the time we're adults, when something as faint as birds chirping or cars driving by can wake us up.
"If we can fall asleep, sounds are often incorporated into our dreams," Glaser wrote. "But it’s the novelty rather than the volume of the noises which we need to tune into. The loud rumble of a regular bus passing outside our window does not trigger us at home, but sleeping in a tent, the full gamut of unusual nighttime activities make themselves heard, so our brain will wake us for a full analysis." People have an especially hard time sleeping in new places, according to a study in Current Biology, possibly due to this same need to monitor our environment for anything suspicious.
While annoying, our tendency to wake up in response to sounds serves an evolutionary purpose: We wouldn't want to sleep through something dangerous. But we've come a long way since the days when we had to watch out for tigers, and now, this ability more often serves to ensure our cats get fed in the morning.