What do two-year-olds know about the sizes of things?

Knowledge about the sizes of things is an integral part of object concepts. In 5 experiments, we examined 2-, 3-, 4-year-olds' and adults' internalized representations of the sizes of buttons, plates, and shoes. We found that 3- and 4-year-olds had accurate knowledge of the typical sizes of buttons and plates. 2-year-olds' knowledge of plate and button sizes was more fragile; however, they demonstrated accurate internal representations of the sizes of shoes. The studies provide new empirical evidence about the young child's knowledge of the sizes of 3 everyday objects. The findings also suggest that the size of an object may be more accurately represented if its size is highly relevant for the object's intended function.