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Dr. Tom Smulders, Newcastle University – Waterlogged Fingers and Gripping Ability

In today’s Academic Minute, Dr. Tom Smulders of Newcastle University explains why our fingers become wrinkly after prolonged exposure to water.

Tom Smulders is a senior lecturer at Newcastle University’s Centre for Behaviour and Evolution where his research focuses on different aspects of spatial information processing, specifically in food-hoarding animals. His work has been featured in a number of peer-reviewed journals and he holds a Ph.D. from Cornell University.

About Dr. Smulders

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Dr. Tom Smulders – Waterlogged Fingers and Gripping Ability

When we soak in a warm bath or do the dishes without gloves, the skin on our fingers starts to wrinkle after a while. Why does this happen?

Received wisdom says that the skin on our fingers absorbs water through the process of osmosis, and therefore swells up. However, when researchers measured the volume of wrinkly fingertips, they found that they had shrunk, not swollen. Just like raisins and prunes, the underlying tissue shrinks, and the overlying skin is now too big, and wrinkles up.

So what makes the fingertip volumes shrink then? According to these same researchers, this is due to vasoconstriction: the tightening of the blood vessels in the fingertips, which allows less blood into the fingertip. This vasoconstriction is controlled by the autonomic nervous system, making finger wrinkling the result of an active neural response to submersion in water.

But why constrict blood vessels when fingers are submerged in water? It is possible that the vasoconstriction serves a purpose of its own, and that the wrinkling is a side effect. However, it is also possible that the wrinkling is indeed the main purpose of the whole process.

Recently, we have shown that people have better grip on small objects picked up from under water when their fingers are wrinkled than when they are not. This suggests that the wrinkles themselves have a function: improving grip in wet conditions. This could be a novel human trait, evolved in the context of tool making or foraging in shallow water. Or it could be a trait we share with other primates, possibly to improve grip when moving around wet rain forests. This is still an open question.

Whatever the reason, though, next time you do dishes, don’t worry about the wrinkles: they may help you not to drop that wet plate.

Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.

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