As the mercury plunged toward zero this weekend, Minnesotans once again pulled on their wool, fleece and fur hats.

Why?

"I heard you lose a percentage of your heat through your head," James Rotman said as he donned a stocking cap while waiting for the light-rail train downtown Monday.

Well, hold onto that hat. A college professor with a quirky YouTube video is out to bust the hat myth.

"Anyone who's lived in the cold ... has been told to wear a hat before you go out because 70 percent of your heat leaves your head. I've even told my own kids this," said Andrew Maynard, University of Michigan professor of environmental health sciences and director of the its Risk Science Center. "But when you look into the science, it doesn't make sense."

Maynard poses the question like this: "Does wearing a hat keep you warm while dancing naked?"

Star Tribune, Star Tribune
Jasmine Brown and her kids, from left, Cortez, Anthony and Damarionna were bundled up — hats and headgear included — against the cold Monday as they waited for a bus in Minneapolis.

He lays it all out in his 2 1/2-minute, fast-action video featuring a naked stick figure topped by a tasseled stocking cap.

Before you know it, Maynard's stick figures have illustrated a 1957 British experiment that measured heat loss by having volunteers "stick their heads in a box and a thermometer up their bottoms." The results led people to believe that at least half a person's heat escaped by way of an exposed noggin. And eventually it became a convenient way for parents to get their children to wear hats, Maynard said.

But in the end, Maynard said, it's not about which body part is exposed but how much. The head accounts for only about 10 percent of a person's body area, so a person isn't going to lose as much as 70 percent of his or her heat through the head, Maynard said. "And what that means is that you can't dance around naked and expect to stay relatively warm by wearing only a hat."

Maynard's light-hearted, stick-figure-in-hat video is among a series he creates weekly to "get people to think a little more critically ... and make sense of all this risk information that they're bombarded with about the stuff in the air or shampoo they put on their head or the food they put in their mouth," he said.

So he's taken on such topics as poop and cellphones, chocolate consumption and Nobel Prize winners and tryptophan and Thanksgiving torpor.

Warm and stylish

Ron Guy, a Minneapolis traffic control officer who spends at least a couple hours directing traffic in and out of downtown, knows a thing or two about staying warm as the mercury plummets. The navy blue stocking cap definitely keeps his head warm, he said. "I'm bald," he added. And when the temps push past 30 degrees, as expected later this week before another big freeze hits Sunday, he switches to a baseball cap. "I don't like showing my age," he said. "And it looks more professional."

But whether or not to wear a hat can be about more than just keeping warm.

"Vanity," said a hatless Laura Clendenin, huddling inside a downtown light-rail train station. "I'm absolutely colder without a hat," she admitted. "It's why I wear my hair down."

Seventeen-year-old Marta Vandertop's solution: "A headband to protect my ears without hat-hair. I want to look good when I go inside."

Iman Mefleh, a cross-country ski racer and winter bicyclist, who offers clinics about dressing to stay warm while enjoying winter sports, advocates wearing a hat in cold weather. "You won't lose 70 percent of your heat without one but you could get frostbite on your ears and your forehead will get cold. You'll stay warmer with a hat," she said.

Maynard concurs. "I wear my wooly hat because I don't like getting cold ears," he said. "The bottom line is you really don't have to wear a hat. But if you feel cozier wearing one, then wear one."

Mary Lynn Smith • 612-673-4788