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616758.  Wed Sep 23, 2009 2:33 pm Reply with quote

Here's a weird one for you...

Shine a small light onto someone's hand. Then turn it off, and ask them to point (with their other hand) to where the light was. Measure how close they get to the actual point it was shone on.

If you shine it onto the palm of their hand, they will be more accurate than if you shine it onto the back of their hand.

The theory is that it's caused by neurons in the brain that carry information about both visual and touch stimuli. Since there are more touch receptors on the palm than the back of the hand, there are more of these "bimodal" neurons, and so you can make a more accurate judgment about visual stimuli as well. There's an article about it in the journal Neuropsychologia, from May 2009...

617002.  Thu Sep 24, 2009 1:27 am Reply with quote

I'd have thought it would be more associated with what is a more "natural" thing to do, and so, practice more.

I suspect we're more spacially aware when using our palms (swinging from tree to tree, throwing, etc). But when the back of the hands comes into play, then you need to mentally swap from back to front which introduces the margin for error.

That's my hypothesis, and I'm sticking to it!

617041.  Thu Sep 24, 2009 3:21 am Reply with quote

There are more reference points on your palm than on the back of your hand, of course (lines and the points where they meet). I dare say the article addresses that point, though.

617161.  Thu Sep 24, 2009 9:26 am Reply with quote

I'm not very good with the palm. I know it like the back of my hand.

617232.  Thu Sep 24, 2009 12:08 pm Reply with quote

Flash wrote:
I dare say the article addresses that point, though.

Or, perhaps it doesn't? (academics have been known on occasions to have a lack of bimodal common-sense receptors)

617244.  Thu Sep 24, 2009 12:25 pm Reply with quote

"I know it like the front of my hand" sounds dirty. I'm sticking with the original phrase.

617251.  Thu Sep 24, 2009 12:42 pm Reply with quote

Well one of the other things they found was that people were more accurate when pointing to their own hand than they were when pointing at a fake hand. So unless the fake hands were really unrealistic (which is certainly possible I guess), there shouldn't be any difference in the number of reference points there.

Practice may have something to do with it, even on a subconscious level. It's been shown that people are more sensitive to visual stimuli that are presented near their hands than ones presented elsewhere.

"I know it like the back of my hand" has always seemed a bit of an odd simile to me. I sure as hell couldn't draw an accurate picture of the back of my hand without looking at it. Maybe that would be a good challenge for the panelists on one episode...


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