What temperature gradations can a person actually feel?
February 4, 2016 11:01 AM   Subscribe

I work some hours every week in a friend's studio. Yesterday she observed that she was chilly, so had put the heat up from 21 to 22 degrees (Celsius).

In the past, in the summer, she has occasionally responded to my comment that it's been too hot in the studio by saying things like "OK, I'll put the AC down from 25 to 24" or something like this.

I have been known to laugh on these occasions, as if adjusting the temperature a single degree either way is going to make much difference. But she maintains she can feel the difference. I maintain she can't, and that most of us will feel a 5-degree adjustment but not an adjustment of a single degree. (That she's a much more sensitive creature than a neanderthal like me is sort of implied, but is not what the question's about.)

Am I mad? Is she? Can you feel a single degree in temperature change?
posted by zadcat to Health & Fitness (47 answers total) 1 user marked this as a favorite
Is it possible she's just feeling the warm air that comes out when the heat first gets turned up, or cold air when the AC comes on?

Can you test it out and "pretend" to put the heat up next time? Please note that I am in no way condoning pulling a ruse on your co-worker but then again I totally am.
posted by bondcliff at 11:05 AM on February 4, 2016 [5 favorites]

What sort of heating system/thermostat does she have?

I ask because I can definitely feel it if I raise the thermostat by 1 degree F in my apartment, because raising it causes the heat to kick on. It's a forced-hot-air system, so the apartment tends to get colder than the setting on the thermostat unless the heating system is actively running and mixing the air around.

That being said, I do feel the difference between 68F and 70F on my thermostat even without the heat kicking in (which is about a 1.1 degree C difference).
posted by pie ninja at 11:09 AM on February 4, 2016 [17 favorites]

The thermostat is one thing, I think, and the actual temperature in the room may be something else. At my house, when I get chilly with the thermostat at its regularly-programmed 65° F, I can bump it up to 67° and be roasting within a few minutes. One factor is whether the furnace has been running. We have gas forced air, and if the sun is shining through the windows, the furnace may not run for awhile. Popping the thermostat up even a single degree above the temperature its measuring in the room results in a big inflow of nice hot air. And conversely for the AC when we kick it up a notch on a hot day. I'm not sure what degree change I might be feeling, but I'm not sure it has a lot to do with the the exact number on the thermostat. If I walked into a 65° room versus a 67° room, I'm sure I couldn't tell you which was which. But if I'm hanging out in the room, I can feel the difference between "the furnace hasn't kicked on for awhile and it's cooling off in here" versus "new hot air has just been introduced."
posted by not that girl at 11:11 AM on February 4, 2016 [4 favorites]

Best answer: Human skin is around 34°C. Rate of heat transfer is proportional to temperature differential; changing environmental temperature from 21°C to 22°C would decrease rate of heat loss by about 8%. That seems like it should be plenty noticeable.
posted by disconnect at 11:12 AM on February 4, 2016 [51 favorites]

I definitely notice a difference of 2 degrees Fahrenheit (1 degree C). 61F is chilly, 63F is cool, and by 65F it's slightly warmer than I like. Also, the heating / AC system will probably move things an additional degree or more C to begin with.
posted by wotsac at 11:12 AM on February 4, 2016 [5 favorites]

My wife and child will argue with me relentlessly that it is "too hot" if I let the temperature in our apartment get to 71 degrees (that's a scosh over 21 C) , because we have reached a Grand Compromise to keep the thermostat at 70. I can't tell the difference, myself, but apparently their delicate constitutions are more finely tuned than mine.
posted by briank at 11:13 AM on February 4, 2016 [3 favorites]

There have been quite a few occasions this winter where I started feeling overheated and slightly ill. I checked the thermostat and every time I found my husband had adjusted it from 68* F to 70* or 71*.
posted by belladonna at 11:15 AM on February 4, 2016 [1 favorite]

Can you feel a single degree in temperature change?

Well, first we have to determine what you mean by 'feel.'

Since our perception of things is mediated (that is, our brains don't just process raw input), we can 'feel' hotter or cooler by knowing we moved the thermostat setpoint. Some places have 'dummy thermostats' for just this reason.

Where the thermostat is placed can also have an effect - a thermostat at waist height, near a door or window, will produce a different feeling in the room than one at head height and far from any leakage or airflow.

So your friend may not be sensitive to a one degree change in air temperature, but making that one degree change on the thermostat is not the same thing...
posted by the man of twists and turns at 11:16 AM on February 4, 2016

People can sense as little a difference as a degree Fahrenheit when e.g. walking from one room to another. This is so well-established that this Scientific American piece starts with this premise and goes on to ask (and answer) how the body can do this. A degree Celsius, being about twice the size of a degree Fahrenheit, should be no problem for most people.
posted by kindall at 11:20 AM on February 4, 2016 [23 favorites]

Yes, some people can tell. She can. Maybe you can't. That doesn't make either of you mad. Why do you "maintain she can't"? She says she can, it's okay to believe her.
posted by sageleaf at 11:20 AM on February 4, 2016 [32 favorites]

I can feel a difference of 1 degree C as well. Even when I don't know someone has moved the thermostat. If someone has exceptional sight or hearing, why can't they have exceptional feeling?

Also, please don't gaslight her and lie about changing the temp.
posted by kimberussell at 11:20 AM on February 4, 2016 [33 favorites]

I can totally feel the difference between 67 and 68 degrees F. 68 is fine, 67 is "it's starting to get chilly" zone.
posted by clone boulevard at 11:24 AM on February 4, 2016

I feel like I can tell the difference between a few degrees. Also depending where the thermostat is in the room can really make a difference in terms of what turning the heat up a degree on the thermostats actually does. So like in my apartment, the thermostat is sort of in a bookshelf, so turning it up a little bit actually makes the room really warm because it takes a while for the thermostat to warm up. I have another place I take care of which has seven thermostats (don't ask) and each of those have a slightly different relationship to the actual temperature of the room. So my vote, if we're voting is "Yes people can totally tell" and since it's her space I'd presume she knows the relationship between temperature and thermostat better than you do.
posted by jessamyn at 11:31 AM on February 4, 2016

If you are feeling scholarly this article might be of interest to you.

In summary people can perceive differences of 0.02-0.07 C, this is measured using heat pulses on hairless skin at the base of the thumb, clothing, body hair & location on body can effect this. The rate of temp change influences how readily people can detect the change. Less than 0.5C per minute then you can be unaware of a 4-5C change. If the skin is in the 30-36C range. Rapid changes of say the .1 C/second range are much more easily sensed.
posted by wwax at 11:32 AM on February 4, 2016 [4 favorites]

In this case, you're dealing with a threshold where, yes, there is a difference of one degree or less between the way she likes it and the way she doesn't. There has to be a line somewhere. It might be more difficult for her to tell the difference between 19 and 20 as both are uncomfortable, though she probably could, if given two rooms to compare between, tell that one was slightly cooler than the other.

The units are in use because they are pretty easily discernable, C even more so than F from one degree to the next. If we were dealing in (this is made up afaik) decicelcius it would be much harder to differentiate between 21 and 22, but still pretty easy to tell 21 from 31.
posted by Lyn Never at 11:34 AM on February 4, 2016

I can tell within 2 or 3 degrees F, so 1 degree C sounds completely reasonable to me. I would get pretty damn annoyed if someone tried to tell me I was just imagining things.

(Actually, because I'm a nerd, I'd probably take it as an opportunity to start running a controlled experiment on that topic. But first I'd get annoyed .)
posted by Stacey at 11:35 AM on February 4, 2016 [1 favorite]

I end up with a big struggle yearly to try to keep my house at a certain temp to save a few dollars; invariably I can't take it and need to push it up that last 0.5 °C; that .5 is quite palpable and it's the difference between constantly feeling cold and achy or warm and comfortable.
posted by kmennie at 11:58 AM on February 4, 2016 [1 favorite]

Absolutely this is possible. 2 degrees Fahrenheit in either direction on the thermostat means I need to start losing or gaining layers. I feel a significant difference.
posted by moira at 12:00 PM on February 4, 2016 [3 favorites]

I live in Florida and we keep our thermostat set at 78 or 79 for the air conditioner throughout most of the year. My husband prefers 79, I prefer 78. I can always tell when it is 78 vs. 79 without looking.
posted by gatorae at 12:05 PM on February 4, 2016 [3 favorites]

At work we have a file room that we keep at 72F, and an adjacent LAN room that is set at 71F. They are both very tightly controlled, properly insulated etc. Very accurate. Walking thru the door to either room is absolutely noticeable either way.
posted by peep at 12:07 PM on February 4, 2016 [2 favorites]

Note: "changing environmental temperature from 21°C to 22°C would decrease rate of heat loss by about 8%. "

Only true if you are measuring in absolute (Kelvin) in which case it's 294 to 295 or about 0.34% change. Probably still noticeable but quite a bit smaller relative change than 8%.
posted by soylent00FF00 at 12:20 PM on February 4, 2016 [3 favorites]

I can consistently and reliably feel a temperature difference of 1/2 degree F.
posted by Corvid at 12:20 PM on February 4, 2016 [1 favorite]


I can also tell the difference between artificial sweetener and natural sweetener, and between organic and non-organic milk.

The question is, why can't you? Maybe your ancestors weren't required to be as alert to possible environmental threats as mine were :)
posted by amtho at 12:35 PM on February 4, 2016 [6 favorites]

Only true if you are measuring in absolute (Kelvin) in which case it's 294 to 295 or about 0.34% change. Probably still noticeable but quite a bit smaller relative change than 8%.

The difference between body temperature and room temperature is what matters, though, rather than the absolute temperature. To be fair, the percent difference in this change isn't a perfect measure of how noticeable a change in temperature is.
posted by cogitron at 12:37 PM on February 4, 2016

1 degree Celsius? Definitely can feel.

Although with a thermostat, the temperature sensor is a bit of a lagging indicator. Some other comments addressed this, but if it's say 28C and I turn the thermostat to 27C triggering the air conditioner, there is now a blast of cold air coming into the room which is easy to feel. But the thermostat is just measuring ambient air temperature and is not as quickly affected (especially if its not in the path of the air conditioner and I am).

That said, even just talking about ambient averages 1 degree Celsius is a noticeable difference (especially if you get hot/cold easily).
posted by thefoxgod at 1:23 PM on February 4, 2016

Only true if you are measuring in absolute (Kelvin) in which case it's 294 to 295 or about 0.34% change.

Doesn't matter if you're measuring in °C, °F, K, or °made-up-unit, Q = k*(T[obj]-T[surr]) where k is determined by environmental conditions. For a 21°C/22°C room and 34°C skin, Q changes from 13k to 12k. Change your units to 294 K/295 K room and 307 K skin, you have the same change in Q. Changing to 69.8°F/71.6°F and 93.2°F, and Q changes from 23.4k1 to 21.6k1, same proportion (different k because different T unit). etc.
posted by disconnect at 1:25 PM on February 4, 2016 [4 favorites]

I totally can. 20C is frosty, 21C is tolerable, 22C is decadent and 23C is tropical.

Same with AC.
posted by St. Peepsburg at 1:32 PM on February 4, 2016 [2 favorites]

I’m only going to pipe in because I’m one of those people who doesn’t care that much about the difference, I’m comfortable in a wide range of temps, mostly on the warm/hot side, but I can still tell the difference pretty easily from just a couple of degrees Fahrenheit.
posted by bongo_x at 1:48 PM on February 4, 2016

Two degrees Fahrenheit is absolutely something I'd feel, at least indoors. (I think we're all assuming a change in indoor, controlled temperatures.) Most of the time, unless I've just come in from the cold outside, 70° will be stifling for me; at 68°, it's perfect. And, for what it's worth, unless I've left the house and forgotten to turn the A/C or heat on/off (as applicable) and am returning to unexpected discomfort, I never adjust the temperature by more than 2 degrees F, which would just about scale to 1 degree C for you.
posted by The Wrong Kind of Cheese at 2:00 PM on February 4, 2016

Yep, I generally run cold, and prefer my house to be at 72F. If it drops down to 70F I can definitely tell, 71F sometimes. If I put the temp up to 74F I can also tell the difference, and it makes me really happy, but everyone else complains its too hot.
posted by Joh at 2:05 PM on February 4, 2016 [2 favorites]

She's not mad. She told you she can tell the difference. Only she knows what her body can feel, not us. You're trying to make everyone the same. Nothing anyone here says about our experience with temperature says anything about her body. And like the person above, I would be annoyed if you laughed at something like this.
posted by Blitz at 2:18 PM on February 4, 2016 [7 favorites]

Yes, this is tested and settled science. People can absolutely sense a 2 degree F (1 degree C) temperature shift, even apart from other factors such as air movement, radiation, etc. Women are more likely than men to have this level of temperature sensitivity.
posted by meinvt at 2:24 PM on February 4, 2016 [7 favorites]

Yup agree with the others. I'm a very sensitive person and can definitely tell the difference between two temps within a degree F. Your response to her btw is insensitive and assumes all humans experience everything equally. None of us taste the same way, see the same way or feel things exactly the same way as someone else. Her experience is just as valid as yours- no one is "mad". I would be really annoyed at you if you laughed in my face and discounted my experience as invalid.
posted by FireFountain at 3:12 PM on February 4, 2016 [2 favorites]

My partner likes the a/c on 24C at night, but that is too cold for me. Our new plan is to put the a/c on earlier but for 25C, and that seems to satisfy both of us. So, I wouldn't assume that your colleague is imagining things. FWIW, I don't think I could detect the difference between 24C and 25C by e.g. walking into different rooms, but over a period of hours one is acceptable and the other is too cold.
posted by Cheese Monster at 3:54 PM on February 4, 2016

(Just to clarify, my example is of cooling when the weather is hot, not heating when the weather is cold.)
posted by Cheese Monster at 3:56 PM on February 4, 2016 [1 favorite]

I used to study chemistry at university, this many access to large water baths for some experimental work. A lab mate of mine was regularly able to guess temperatures to within 0.5C.
posted by biffa at 4:07 PM on February 4, 2016

Anecdata: indoors and clothed, I personally can't tell (I can tell if the heat suddenly kicks on, though.) In a pool, I can tell within two to five degrees F. It's not unreasonable that someone else can tell. People I've lived with who are thinner than me have a more sensitive personal thermostat; my sister who has significantly less fat and muscle is the canary in our house for when the heat goes off.
posted by blnkfrnk at 4:22 PM on February 4, 2016

I've had the heat on a lot this winter. 70 on the thermostat isn't warm enough but 71 is just right. At 72 I start to feel like I can't breathe the hot air. I think it means the heater comes on just enough more frequently that I'm comfortable.
posted by cecic at 4:52 PM on February 4, 2016 [1 favorite]

I am not someone that is particularly aware of me and my body. I have a headache and ignore it. My doctor told me I had mono but I never knew it.
But- 70 is chilly in my house. 71 is great. 73 and it is way too hot.
posted by ReluctantViking at 6:56 PM on February 4, 2016

Mea culpa on the 8% thing: I was being far to literal and thinking of only the black-body emissions (which does not change 8% with a 1C change, but rather does indeed prefer a proper ratio scale measurement such as Kelvin).

But of course the inward heat flux is not zero, so that was kind of a stupid comment to make.

However, if one is sitting naked in a perfect absolute zero vacuum...
posted by soylent00FF00 at 8:06 PM on February 4, 2016 [3 favorites]

My comfortable temperature range varies slightly throughout the day (I prefer it a little warmer at night), but it's a) much higher than most people's and b) very, very narrow.

My thermostat has a half-degree tolerance, which means that if I set it at 24, it turns on at 23.5, heats up to 24.5 and then shuts off. I can tell when it's about time for another burst of warm air, because the difference between 24.5 and 23.5 is entirely noticeable to me. I might not actively notice the temperature dropping as it is happening, but shortly after my toes start to get cold, the furnace will turn back on.
posted by jacquilynne at 8:24 PM on February 4, 2016

Just chiming in to say that everyone uses units that double as heating/air con in parts of China, where I used to live, with a remote control for the temperature which was in Celsius, so I have lots of experiences adjusting by one or two degrees, and it definitely makes a difference; 2 degrees celsius was a big difference, one degree was noticeable. 5 degrees would be huge.
posted by bearette at 8:27 PM on February 4, 2016

I used to have a motorcycle with a digital thermometer. I would often be driving, feel a temperature change, and look down to find the thermometer had registered a change of one degree F.
posted by counterfeitfake at 8:46 PM on February 4, 2016

In our house my wife is very aware of ½°C changes in the thermostat. I can usually tell within a degree or so.
posted by blue_beetle at 3:22 AM on February 5, 2016

I think it depends how controlled the environment is, and what your personal threshold for feeling cold/hot is. . At my old house, I was constantly freezing or totally comfortable on different days during the winter despite the thermostat not changing, so i rarely noticed when it was adjusted a degree or two... unless it was set even 1 degree below 21C...then i could never get warm, ever.

Very similarly, last winter i was always complaining about being cold at my boyfriend's, who kept his house set at 20C. I'd stay wrapped in blankets at all times during the day and still be cold. One weekend I mentioned how weird it was that i wasn't cold for once, and he said he had turned it up to 21C. So there's a one-sample blind experiment for you. He keeps it at 21 now and it's great. Sometimes i even take my sweater off :)
posted by randomnity at 6:21 AM on February 5, 2016

Best answer: Also zadcat, like you, my boyfriend thinks it's weird that i even noticed any difference with 1C...but I'm pretty sure it's because his "cold" threshold is set at a much lower temperature than mine. I bet he'd be more sensitive to a 1C temperature around that threshold for him.

And similarly, i had a roommate who was constantly overheating, and turning the AC down a degree or two was huge for him whereas I couldn't really feel any difference. So I suspect your hot/cold discomfort thresholds are more relevant than your absolute sensitivity to temperature changes. Maybe that's the case with you and your friend, too?
posted by randomnity at 6:31 AM on February 5, 2016

Yes, I can feel a one-degree difference and if you think you can only feel a difference in temperature at intervals of five degrees, I respectfully think you are quite mistaken. Five degrees is a massive difference.
posted by AppleTurnover at 10:50 AM on February 5, 2016

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