Why Do Your Fingers Prune Up In Water?

it was originally thought that osmosis caused the skin to become water logged. Studies showed, However, that fingers with damaged nerves would not wrinkle after being soaked in water.
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it was eventually determined that the wrinkling was caused by the constriction of multiple blood vessels beneath the skin and is the result of an involuntary nervous system reaction.

one study tested whether people with and without wrinly fingers could pick up and move wet marbles from one box to another. Prune fingers were more efficient. A reproduction of this study could not confirm the result.