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Aristotle's Nose

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Edited by Richard Walker, Wednesday, 9 Jun 2021, 00:19

When we were very young we were shown the ‘two noses’ illusion by my Dad.

If you cross your fingers and touch a small object (such as the tip of your nose), there will seem to be two of whatever it is. Not being able to see the object strengthens the illusion, and because you can’t see the end of your nose very well it is a suitable tactile target. Besides, using your nose is amusing.

This illusion has been known for at least two thousand years. Aristotle wrote (Metaphysics Book 4):

“… touch says there are two objects when we cross our fingers, while sight says there is one”

It’s an example of a tactile illusion. There are a lot of optical illusions known but illusions of touch are less common.

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Hello Richard


Are you familiar with the McGurk Effect? It seems to work in a similar way...

                          McGurk effect - Auditory Illusion - BBC Horizon Clip           

My own view is that our brains are only able to process one source of sensory information at a time, and when more than one source is available, the brain gets 'confused' and can't function correctly. This is why people get 'tricked' by these illusions...

It's obviously some kind of evolutionary defect. 


Mc Gurk

Yes know about the McGurk effect, I recorded myself saying ba ba ba..., then looked in the mirror while I played it back, and by silently mouthing pa pa pa... and da da da... heard those sounds, even though objectively the recording was ba ba ba. I'll put up a posting that I wrote somewhere else.

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Yes, I would like to read that.

That's incredible that you are able to effectively fool yourself this way. I have found that my brain 'flips' between the two sounds (ba, ba, ba and fa, fa, fa)  whenever I watch the above video ~ but that is because I am anticipating the effect and trying not to be 'tricked'. When I first came across it, I was completely fooled.