All That Glistens: II. The Effects of Reflective Surface Finishes on the Mouthing Activity of Infants and Toddlers

Abstract

A number of infants and toddlers have been observed to mouth and to lick the horizontal metal mirrors of toys on their hands and knees in a manner not unlike the way older children drink from rain pools in developing countries. Such mouthing of glistening surfaces by nursing-age children might characterize the precocious ability to recognize the glossy and sparkling features of water long before this information is useful later in development. Two experiments examined the frequency with which infants and toddlers mouthed lightweight 25.4-cm diameter dinner plates during 5 bouts of plate contact. Experiments were conducted in the natural context of toy handling during playtime at 10 day-care facilities in northern California. In the first experiment, 22 children divided into 2 age groups (13 between 6 and 12 months and 9 between 13 and 17 months) were examined as they handled or contacted a stainless steel plate with a mirror finish or a glossy white plastic plate. The stainless steel plate was mouthed at a significantly (p < .0001) larger percentage of plate-contact bouts than the white glossy plate, with no appreciable difference in age. Consistent with observations that some forms of mouthing resembled drinking activity, children mouthed the stainless steel plate on their hands and knees significantly (p < .025) more than the glossy white plate. The 2nd experiment compared teal-blue plastic plates with plates that had glossy and dull surface finishes. Forty-six infants and toddlers in 3 age groups (7-12 months, 13-18 months, and 19-24 months) handled or contacted both plates for 5 bouts. The glossy plate elicited a significantly (p < .05) larger percentage of mouthing than the dull plate, but this effect was restricted to the youngest age group. Mouthing of both plates increased markedly in the oldest age group, a result that likely characterizes the association of dinner plates with eating. Together, the results of these experiments suggest that infants and toddlers have the precocious ability to recognize the optical cues for water as characterized by the gleaming highlights and clear reflections of polished metal. The reduction of mouthing of the teal plate with a dull surface finish provides ideas for thwarting mouthing that endangers children by applying dull surface finishes to potentially hazardous household objects known to have caused incidences of suffocation, choking, and the transmission of pathogens by saliva.