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The Impact of Water - Induced Finger Wrinkles on Object Manipulation

JSHS · 2025

Lily Anderson, Daisy Huang · B.E.S.T. Homeschool, Fairbanks, AK

Overview

This study investigates whether the active nerve reflex that causes finger wrinkling upon water exposure enhances the ability to manipulate wet objects. Finger wrinkling, caused by vasoconstriction in the fingertips, has been suggested to provide an adapti ve advantage by improving grip in wet conditions. However, previous studies using only small, rigid objects like marbles have yielded mixed results. This research expands on prior work by incorporating larger and deformable objects to better represent organic materials that early humans may have handled in wet environments. This research expands on prior work by incorporating larger and deformable objects to better represent materials that early humans may have encountered in wet environments. Using a withi n-subjects design, fourteen participants completed timed object manipulation tasks involving small and large marbles, grapefruit, water balloons, and Orbeez under two conditions: wrinkled and non-wrinkled fingers. Objects were transferred between water- filled containers through a 10 cm diameter hole in a plexiglass screen. We also measured the coefficient of friction between the fingers and hard or squishy surfaces using a custom -built tribometer. On average, participants performed better with wrinkled fingers across all objects, but only the Orbeez trials showed a statistically significant improvement of 20%, with average times decreasing from 53 to 42 seconds. Tribometer tests revealed a 14% increase in friction in the wrinkled condition when interacting with squishy surfaces, but no meaningful difference with hard surfaces. These results support our hypothesis that finger wrinkling may offer an evolutionary advantage for gripping pliable, wet objects rather than rigid ones.

Competition history

  • JSHS 2025 Category not listed

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