Children's use of everyday artifacts: Learning the hidden affordance of zipping.

The everyday world is populated with artifacts that require specific motor actions to use objects as their designers intended. But researchers know little about how children learn to use everyday artifacts. We encouraged forty-four 12- to 60-month-old children to unzip a vinyl pouch during a single 60-s trial. Although unzipping a pouch may seem simple, it is not. Unzipping requires precise role-differentiated bimanual actions-one hand must stabilize the pouch while the other hand applies a pulling force on the tab. Moreover, kinematic data from six adults showed that the tolerance limits for applying the forces are relatively narrow (pulling the tab within 63° of the zipper teeth while stabilizing the pouch within 4 cm of the slider). Children showed an age-related progression for the unzipping action. The youngest children did not display the designed pulling action; children at intermediate ages pulled the tab but applied forces outside the tolerance limits (pulled in the wrong direction, failed to stabilize the pouch in the correct location), and the oldest children successfully implemented the designed action. Findings highlight the perceptual-motor requirements in children's discovery and implementation of the hidden affordances of everyday artifacts.