Amount Versus Number: Infants' Use of Area and Contour Length to Discriminate Small Sets

Previous research has reported that infants use amount rather than number to discriminate small sets (Clearfield & Mix, 1999). This study sought to replicate and extend this finding. Experiment 1 confirmed that infants respond to changes in contour length but not to changes in number when contour length is controlled. However, contour length and area were confounded in this experiment and the original study. To determine what specific measure of spatial extent infants use to discriminate small sets, Experiment 2 included 2 conditions that varied either area or contour length, but not both. As before, infants responded to the changes in spatial extent-either contour length alone or area alone-but not to the changes in number.