When is four far more than three? Children's generalization of newly acquired number words.

What is the relationship between children's first number words and number concepts? We used training tasks to explore children's interpretation of number words as they acquired the words' meanings. Children who had mastered the meanings of only the first two or three number words were systematically provided with varied input on the next word-to-quantity mapping, and their extension of the newly trained word was assessed across a variety of test items. Children who had already mastered number words to three generalized training on four to new objects and nouns, such that their representation of the newly learned number was approximate. In contrast, children who had mastered only one and two learned to apply three reliably within a single count-noun context (e.g., three dogs), but did not generalize training to new objects labeled with different nouns (e.g., three cows). Both findings suggest that children fail to map newly learned words in their counting routine to the fully abstract concepts of natural numbers.