Temperature Sensitivity and Perception

It does not seem like the question is asking the observer to compare the temperature of the person with a fever to the temperature of water.

Though the water and fever seem to be about the same temperature, there are some other things to consider.

Skin generally does not "feel" body temperature to the touch. So, even though body temperature is close to the same as the water's temperature, it "feels" different.

Also, a person with a fever "feels" hot - heat is being dissapated by the skin, so it feels as though heat is radiating from the skin and body. I would liken it to holding a hand over the top of boiling water.

Does that answer the question?

It's a matter of perception. Many years ago I worked as a baker, (to put myself through school) as a short cut, I found a way to determine the difference between 98F and 100F when I needed to activate the yeast. I changed the water temperature until I could no loner feel a temperature. It didn't feel hot, it didn't feel cold, it just felt wet. Then if you achieve that, check and you'll see the temp. is just about 98F.

As for a person, they normal don't feel warm to the touch, but if they are running a fever, they do seem to feel warm to the touch.

Thank-you for your attempts.

Still digesting your comments,But just thinking if it has to do something with natural instinct?

In my opinion it is not related to natural instinct but rather conditioned perception.

How about this:

The human hand, when it's not touching anything, is sensing the temperature of the air around it. Also, this sense is dependent on humidity since humid air "feels" hotter than dry air even if the temperature is the same.

So, if I dip my hand in 98°F water, I can sense that it's warm. If I dip my hand in 100°F water the next day, I won't be able to tell that it's warmer than the previous day's water but I can still sense that it's warm. Warmer than the surrounding air, that is.

So, you're asking, "so why can't I sense that my 98°F forehead is warm".

The answer is, because your skin is not at 98°F.

You're referring to the normal oral temperature of about 98°F (where the doc sticks his poisonous mercury thermometer into your mouth). Skin temperature (the one on the hand in particular) is actually cooler than that. The evaporation of sweat has a cooling effect on the skin which is how our bodies regulate our internal heat.

Hope this makes sense.

regards,

Vulcan

To understand the answer to your question one needs to understand how the body senses temperature and secondly how the brain interprets it.

The nerve endings in the hand do not actually measure temperature or sense temperature, but they do sense the difference in temperature. Your brain has as a reference the temperature of the hand and senses the difference in temperature between it and an object it touches by means of the rate of heat flow in or out of the hand or, more precisely, the rate of temperature change of the sensing nerve due to heat flow rates. It will actually require a couple examples to fully illustrate these concepts. Your brain needs a reference to relate the sensed temperature to. Sometimes it is simply the surrounding tissue, other times it is a memory reference to a frequent experience of heat or cold.

1. Assume that your hand is at 90 degrees. You grab a carboard box full of popsicles out of the freezer. The box is 0 degrees. Because there is a large temperature difference, you can tell that the box is cold but it doesn't feel very cold compared to a metal can of frozen peaches at 0 degrees that you pull out of the same freezer. The can feels expremely cold. Why the difference? The difference comes from the fact that the metal is a very good conductor of heat while the cardboard is an insulator. For an insulator heat flow is very small even at large temperature differences compared to a good conductor. Consequently one senses the can as being very cold and the cardboard as merely being cool. Interestingly, you may actually sense more cold from the cardboard than is actually flowing into your hand because you have touched room temperature cardboard before and because this is cooler than other cardboard you've touched as well as the fact that since you just pulled it from the freezer your brain expects it to be cold.

2. Assume your hand is 90 degrees and the metal object you touch is 92 degrees. In this case the metal may feel slightly warm despite the high thermal conductivity because the heat flow is very small due to the temperature difference being small. Note that this sensed temperature has nothing at all to do with this metal being 92 degrees hotter than the metal can from the freezer.

3. Take 2 copper pipes. Assume that the water in one pipe is 60 degrees. Our hand is 90 degrees so when we touch it, it feels nice and cool but not uncomfortable because we have a 30 degree temperature difference with a good conductor. Assume the water in the second pipe is 120 degrees. If we touch it, it feels nice and warm because we have a 30 degree temperature difference with a good conductor. Now grab one with each hand. One feels nice and warm while the other feels nice and cool. Now lets assume that in one section of pipe, these two pipes are twisted tightly around each other. You grab the entwined pipes with one hand and immediately think that you are getting burned. Why? Because in areas immediately next to each other on your hand you are sensing a 120 degree to 60 degree temperature difference since they reference each other. This is a 60 degree difference. 60 degrees above your hands 90 degrees would be 150 degrees which would scald you . It feels hot! Of course 60 degrees below your 90 degree hand is 30 degrees which is just below freezing. Either way it is a shock and your hand senses that it is being burned. It is not of course since we are only using cool and warm water. Your hand, however, is sensing the difference between the two.

Now to your questions example. You put your hand in 98 degree water. Water is a pretty fair conductor of heat and you sense warm water with your 90 degree hand. Now, a day later you put your hand in 100 degree water. Again you sense warm water, but the 2 degree difference between the two buckets of water is only one fifth of the temperature difference you are sensing. There is also no reference to the water temp from the day before. Which was warmer? Who knows. It is virtually impossible to tell. Two scenarios would allow you to tell the difference. 1. If you touched 98 degree water every day for a very long time, you might be able to tell the difference with the 100 degree water since your brain has built up a pseudo reference of your experience over time. 2. If you touched one immediately after the other, you now have a temperature reference and you will immediately know which is warmer - even with only two degrees - especially if you let your hand come to water temp in one of the two buckets.

Now you touch the persons forehead. You sense the temperature difference between your 90 degree hand and their 99 degree forehead. Their skin feels hot and you know they have a fever. You have also your brains pseudo reference because you touch skin, others or your own on a daily basis. You also know from this pseudo reference that they have a fever because they feel warmer than usual.

Hopefully this clears up your question.