{♫Intro♫}.

Negotiating thermostat settings can be one of the most frustrating squabbles you'll ever have. Whether it's family or roommates, or co-workers or classmates, finding that Goldilocks temperature that will suit everyone can be rough.

You'd think it would be easier for us all to agree on a comfortable temperature. I mean, we're all human. But there's actually a lot of biology and psychology explaining why different people experience ambient temperatures differently.

It all starts with your skin, which is covered in sensory nerves called thermoreceptors that send impulses to your brain, keeping it up-to-date on the temperature. Your brain uses this information to keep your body temperature stable and influence your behavior so can you be comfortable as possible— like putting on a hoodie in a chilly room, or peeling off your winter coat on the first day of spring. People generally feel most comfortable somewhere in between the point where they start shivering and the temperature when they start sweating.

In both of those instances, the body has to do something to stay comfortable. But within that range, there's what scientists call the thermal neutral zone, or TNZ. That's the range of ambient temperatures where you can regulate your body temperature through dry heat loss alone.

That essentially means you can stay comfy just by losing heat to your environment—like, the heat that radiates from your skin. Some studies investigating the human TNZ place it somewhere between 28 and 32 degrees Celcius, but it varies a lot from person to person and place to place. And there are a lot of reasons for that variation.

Like, if that range seemed hot to you, that's because it's for naked people. And your TNZ is affected by the clothing you wear because that changes the amount of insulation you have. It's affected by the clothing you wear, for example, because that changes the amount of insulation you have.

But there are features inherent to your body that affect it, too. Like, your metabolism—the cellular activity that keeps you alive. People with higher metabolisms produce more heat.

So, all other things being equal, they'd have lower TNZs. Of course, all other things are never equal. Like, since fat is great insulator, people who have thicker layers of subcutaneous fat are more likely to have a lower TNZ.

Body shape also plays a role—theoretically, since a lot of heat loss occurs via your skin, the more skin you have, the more heat you can lose. But, the more tissue you have overall, the more heat you produce in the first place. So researchers generally talk about body surface area to mass ratios.

The larger the ratio, the harder it is to maintain heat. And this may partly explain why women tend to feel colder than men at lower ambient temperatures. There are always exceptions to this, but on average, men tend to be larger than women—they're typically taller, wider, and heavier.

That means they have more skin, but also more tissue overall, so their surface area to mass ratios tend to be smaller than those of women. That could shift their TNZs downwards. And since women have larger surface area to mass ratios on average, they probably don't retain heat as well, so their TNZs are shifted upwards.

But let's remember, this isn't just a gender thing. This is a body size and shape thing. Like, there's no way Hafþór Björnsson, Kit Harrington, and Peter Dinklage all have the same thermal neutral zone.

Body shape and composition can also help explain age differences in TNZ. Newborn babies are essentially adorable bags of fat, which you might think would keep them warm. But all the fat in those chunky wittle thigh rolls is simply not enough to compensate for the heat they are losing through their skin.

The surface area to mass ratios of infants are, on average, twice those of adults. And accordingly, their TNZs are much higher, just like on the other end of the age spectrum. In the elderly, the thermal neutral zone seems to be higher and narrower.

That's partly because people tend to lose some of their heat-generating muscles and insulating fat as they age. Some scientists believe the elderly also have a harder time regulating temperature in general, thanks to age-related changes in their blood vessels. And really, there's all kinds of stuff going on in our bodies and brains that can impact how we perceive our environment.

Like, having low thyroid hormone levels, or hypothyroidism, can lead to an increased sensitivity to cooler temperatures. The condition slows your metabolism down, so you produce less body heat—and that can leave you feeling really cold even though everyone else around you is cozy as can be. And then there's Raynaud's Phenomenon, a condition that causes blood vessels in the fingers and toes to constrict when a person gets cold or stressed out.

When this happens, warm blood can't get to the skin as well, so a person's digits feel especially cold. If you feel cold all the time and you're concerned about it, you should definitely talk to a trusted healthcare professional. It never hurts to get things checked out.

But the good news is nobody can catch “feeling cold” from you. Or... can they? There is actually a real phenomenon known as Temperature Contagion, where just looking at someone who appears cold or hot can make you feel colder or hotter, too!

For example,in a 2014 study, when healthy volunteers watched videos of people putting their hands in visibly cold water, their hand temperatures actually decreased. And remember, your sensing of the ambient temperature around you starts in your skin—so if your skin temperature changes, so does your evaluation of your environment. So whether it's a trick of the mind, the result of a medical condition, or simply the sum of body shape and composition, different people experience a room's temperature differently.

Now, this might not seem like a big deal—but it can be, because being outside your TNZ messes with your head a little. For example, a 2019 study actually found that women scored significantly better on verbal and math tests in environments that were just a few degrees warmer than the standard settings for air-conditioning. And the shift didn't significantly harm the men's scores.

That's likely because feeling cold impedes some cognitive processes—basically, you can't think as clearly if your body has to devote a lot of energy to keeping you warm. So it might be worth considering upping the thermostat a few degrees if it means the overall performance of the office will improve. Of course, the thermostat wars probably won't be ended so easily, since there are just so many factors that affect how different people feel at a given temperature.

But hey, it's a start. Thanks for watching this episode of SciShow! And a special thanks to all of you who support what we do, including our channel members and Patreon patrons.

If you want to learn more about how humans regulate temperature, you might like our episode on why body-temperature air feels hot. {♫Outro♫}.