After decades of wondering, an NPR reporter finally figures out how her husband's family dog, Donut, knew when the school bus would arrive every day. She did some digging — and now it all makes scents. It turns out, she could smell time, says psychologist Alexandra Horowitz, who studies dog cognition at Columbia University and Barnard College. "I'm not at all surprised that Donut would be able to predict the arrival of the school bus," says Horowitz. Dogs, like people, use many environmental cues to estimate the time during the day, she says. They listen to their body's physiological signs, such as a growing rumble in their tummies, hint of drowsiness or a growing need to ... you know, go outside. Just like humans, they have fluctuating hormones that help create a built-in clock in their bodies and minds. They also look at the amount of light shining into a room or even the angle of the sun. "Both dogs and humans notice, 'Oh, it's getting a little bit dark in the room,' " Horowitz says. But Donut, she says, likely has another trick up her furry leg that we humans don't use to tell time (or at least we don't realize we use): "That's olfaction," Horowitz says. "Dogs are living in basically an olfactory world, and I think they are able to track time with smells." Tap the link in our bio for more. (Images: @heylauragao • Laura Gao for NPR)