Similarity and numerical equivalence: Appearances count

The present study investigated whether preschool children recognize numerical equivalence between sets that vary in similarity. The relation between emergence of accurate numerical equivalence judgments and acquisition of the conventional counting system was also explored. The results of this investigation provide evidence for two main conclusions. First, the ability to recognize numerical equivalence for different sets emerges gradually during the period from 3 to 4 years of age depending on the degree of overall similarity between the sets. Second, conventional counting ability is linked to success on some but not all comparisons, suggesting that acquisition of the labels for various set sizes might aid in abstraction of numerical relations.