Scientists believe our fingers and toes get “wrinkly when wet” for which of the following reasons?

When your fingers start to look like prunes, does that mean it’s time to get out of the tub?

For decades people have assumed (or been told by their parents) that the wrinkling is the result of water passing into the outer layer of the skin, making it swell. Fingers and toes which could double as raisins have long been considered to be sort of a personal, built-in, bath timer.

Now scientists believe those wrinkled digits are actually an involuntary nervous system reaction that gives humans a better grip on wet objects. Laboratory tests have confirmed a theory that wet, wrinkly fingers do indeed improve our grip on wet or submerged objects, working to channel away the water, much like the rain treads on a car tire.

In the study, participants picked up both wet and dry objects, including marbles of different sizes, using both dry hands, and fingers which had been wrinkled by soaking in warm water for 30 minutes. The subjects were faster at picking up wet marbles with wrinkled fingers than with dry ones; the wrinkles made no difference when moving dry objects.

Wet, puckered fingers may have been a great help to our ancestors who literally needed to get a grip when gathering food from wet vegetation or streams. In the same manner, wrinkled toes would have afforded better footing in wet weather or soggy areas.

Even though puckered digits are apparently no longer useful for timing a soak in the tub, they still serve a purpose today - helping us grip wet dishes in the sink.