Learning about what fits: Preschool children's reasoning about effects of object size

Preschool children's understanding of the mathematical significance of unit size was examined through problems that involved making judgments about the number of larger objects versus the number of smaller objects that would fit in a container or bounded space. Children's judgments about effects of object size were elicited both before and after the presentation of a series of demonstration trials. The accuracy of children's judgments about the effects of object size improved significantly from pretest to posttest, and the degree of improvement was similar for 3-year-olds versus 4-year-olds and for Head Start children versus children who attended private preschools. The Head Start children, however, were much less likely than their peers attending private preschools to be able to articulate relevant quantitative features when asked to explain the outcomes that they observed during the training trials.