If you shut your eyes and move your hand in front of them, you think you can see the outline of your hand. I used to be a cave trip leader. We'd take people dee

If you shut your eyes and move your hand in front of them, you think you can see the outline of your hand. I used to be a cave trip leader. We'd take people deep in a cave, turn all lights off, and ask them to put their hand in front of their face. They swear they can still see the outline of it. I would then instruct them to put their hand in front of the person next to them. They can't see it. Seeing your own hand is psychological, not physical. I wonder if this palm-to-ear trick is the same way in an anechoic chamber with another person.