There’s a behavioral component and a physiological component to blankets, reports Atlas Obscura.

About 60 to 90 minutes before a usual bedtime, the body starts losing core temperature. There’s a physiological explanation for that: when the body is heated, we feel more alert. And conversely, when the body cools down, we tend to feel sleepier. Cooler internal body temperatures are correlated with a rise in melatonin, a hormone that induces sleepiness. A bunch of doctors tested this out by making people wear skinsuits—they kind of look like cycling outfits—that dropped their body temperature just a touch, one or two degrees Fahrenheit, to see if they’d sleep better. They did.