At least once every winter, someone will repeat how you should wear a hat in cold weather because you lose 60% (or some other arbitrary percentage) of heat through your head. I’ll bet someone, probably your mom, has already told you that this year. But is it actually true? Like a lot of things in life, it’s a trickier question than it seems.
The origin of the “losing heat through your head” myth
According to The Guardian, the origin of the “losing heat through your head” myth is a “vaguely scientific” experiment conducted the U.S. military in the 1950s, where subjects were dressed in cold weather survival suits designed to keep them warm but not given hats. In those situations, according to the study, people lose most of the heat through their heads. Even though this study wasn’t about normally-dressed people wearing hats versus not wearing hats, people started repeating the “you lose the most heat through your head” thing, and it caught on.
In the most basic terms, we “lose heat” based on how much of our body is covered. Since our heads accounts for about 9% of our skin surface, we save about 9% of heat by wearing a hat. There are other variables—your head isn’t very fatty, but it is covered in hair—that may change the margins a bit, but not wearing a hat accounts for around 7-10% of bodily heat loss. But it’s also complicated by understanding that “losing heat” isn’t about how cold we are, but how cold we think we are.
You’re only as cold as you feel
Dr. Gordon Giesbrecht is a thermophysiologist at the University of Manitoba in Canada and a worldwide expert on being chilly. To truly know the cold, Dr. Popsicle (as he’s known) has leapt into frozen lakes and literally injected ice water in his veins. According to Dr. Giesbrecht, cold is somewhat subjective. “The attitude you have does make a difference,” he told Accuweather. “If you are gonna say, ‘Oh, I’m going to freeze,’ you’ll just be really uncomfortable as opposed to if you say, ‘It might be cold out here but I’m going for a cross-country ski…’ Your mind is taken off the cold because you’re into the activity.”
While you can feel less cold if you think warm thoughts and can physically acclimate to cold weather if you expose yourself to it, there are limits. When it’s cold, blood vessels in our arms and legs constrict. No matter how sunny your disposition, blood flows away from the fingers and toes to keep your brain and other organs warm, and you’ll eventually get frostbite, even if you think warm thoughts.
That physiological response might help explain why we feel like we should cover our heads first. According to hypothermia expert Dr. Daniel I. Sessler, the face, head, and upper chest are up to five times as sensitive to changes in temperature as other areas of the body. If they’re exposed to low temperatures, it will probably make you feel colder, even if you aren’t actually colder. So maybe your mom was a little right after all, in a certain sense, with caveats.
Unless it’s so cold that you’ll get frostbite, whether you should or shouldn’t wear a hat is a personal decision, but there’s usually an obvious answer: As Dr. Popsicle explains it, “You’re not going to become hypothermic through your head. But, on the other hand—I’ve got a pretty scientific view of this—if your head is cold, put a hat on.”
