Thermal Grill Illusion | Hacker News Reader

Thermal Grill Illusion

en.wikipedia.org

92 pointsZeljkoS31 comments

This article needs a rewrite. I can't understand what's going on here:

> But if the person presses against only a cool bar, only coolness is experienced; if the person presses against only a warm bar, only warmth is experienced.

> Researchers have used the illusion to demonstrate that burning pain sensation is in fact a mixture of both cold and heat pain and that it is only the inhibition of the cold pain "channel" that reveals the heat component.

How does the point about inhibition follow from the experiment? Is the cold pain channel somehow inhibited by the grill, but still active when only touching the hot part? idgi

> burning pain sensation is in fact a mixture of both cold and heat pain

Hmm, interesting. I know I'm off at a tangent here, but as an aside, I have small fibre neuropathy and struggle to describe the pain - sometimes I think it's more like a burning sensation, other times I think it's more like a painfully cold sensation.

Geez glad I’m not the only one. Can’t here to find a cogent description.

> Is the cold pain channel somehow inhibited by the grill

No, cold-pain channel is inhibited, when you touch something normally hot. When you touch something very hot, hoth channels fire and you have "burning hot" sensation. So when you touch something normally hot and cold which are very near on your body, you have overlap (like blurring of channels) and you feel that it's burning your skin.

They had one of these at the Expolratorium in San Francisco for many years. I’m not sure if it survived the move to the new location. As a boy I was astounded that my brain could be so easily tricked. Putting my hand on the grill is a vivid childhood memory.

I’m pretty sure it was still there when I went a few years ago!

Vivid for me as well. This and seeing something levitate there as a child changed my life.

I'm currently trying to build a science museum in Arkansas with the Exploratorium as guiding ideal.

Pretty good visual explanation of the "grill" and its effects: https://www.youtube.com/watch?v=otweN9sCSd8

I think I have experienced this when accidentally placing a MacBook (after a few minutes of heavy CPU usage) in my belly skin, below the belly button. The body of the notebook is a bit hot, while the screen itself is cold (or it feels colder due to the aluminum). If both parts touch the screen you feel like you are burning, but if you only touch one of te two parts it's ok.

That could be a short caused by a poorly grounded power supply, and you are just getting electrocuted.

I can second this experience.

I’ve also experienced this with a different laptop.

Tried out the finger version with three glasses of water. I could only reproduce it partway - my middle finger felt like it was in hot water, when it was actually in cold.

Glad I’m not the only one! Since I was in the kitchen when I read this, I had to try. Same result, all three fingers felt like they were in warm water.

All three of mine felt like they were in a hot cup of coffee. The faster you put your fingers in, the more intense the sensation in my experiments

I felt the correct temperatures in all fingers.

I'm starting to think this whole concept is bogus or at least very variable across people.

I've tried this in a classroom settings (with the pipes) - it definitely works.

Quoting Wikipedia (emphasis mine):

> for some people the brain is tricked into thinking the middle finger is in the warm water

It worked for both me and another willing participant, but we found it depended on the orientations of our fingers.

I added the for some people :)

The wikipedia article actually uses the phrase "for some people the brain is tricked into thinking..." so this is exactly as described.

Yes, I edited it to say that

Interesting... Original research is not welcome on Wikipedia. The hedge "for some people" is probably not wrong, but how do you know you actually set up the experiment correctly?

There's hardly any citations in the whole article so how is the reader to know?

Similar experience. And it wasn't foolproof, I could feel the conflicting sensations, and detect that it was not quite right.

Someone ought to make a thermoelectric/peltier toy version of this illusion. Would be good for a Curiosity Box or something of the sort.

I've used the Coolworks IceProbe, a peltier cooler with a heatsink and fan, for cooling drinks at my desk and for the custom cat fountain I made for my kitties [2] [3]

Email me (address in profile) if you'd like the plans for my silver-infused (antibiotic) NSF-grade 0.5 micron filtered cat fountain. I spent over three years perfecting it.

[1] https://en.wikipedia.org/wiki/Thermoelectric_cooling

[2] https://pentairaes.com/coolworks-ice-probe-reg.html

[3] https://photos.google.com/share/AF1QipO871ejy0WcW85ACBSq8Ue8...

https://www.youtube.com/watch?v=otweN9sCSd8

No need for electricity. Just make a grill of angled metal bars, alternatingly going into hot and cold water below.

I'm throwing my butter knifes in the freezer and hot water right now. Let's see how it goes :)

edit: inconclusive. temperature is a bit hard to control. even with the chunky knife handles.

There used to be a demo in Epcot (‘The Body’?) which had two coils, one cold and one heated.. they were separate at the ends, so you could feel the difference. In the middle, they were interleaved, and if you put your hand on it, it would feel simultaneously hot and cold. Cool demo.

They have this at the Exploratorium, too!

I have a spot on my chest that when I pinch it I get convincing feeling of being pinched on my leg.

Which just tells me our abstract, layman understanding of how sensory communication works may be far from truth.

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