Linguists and philosophers have argued that the ability to use language — to learn symbols, to learn patterns of words and inflections, to make sense of utterances and produce one's own utterances, and to situate these utterances in conversations — must be a special, evolved human adaptation. What is special about, for example, children's ability to learn and use words? Are children ‘little sponges,’ ready to absorb a new lexicon with astounding speed? Or is word learning a twist on everyday learning by children and adults? Our research has exposed several pervasive myths about children’s word learning.

Children must learn a wide range of abstract concepts to reason about complex phenomena. For example, concepts like mammal explain why dogs and dolphins are in some ways more similar than tuna and dolphins. Concepts like intention refer to ineffable states of mind that are not always paralleled by actions. The concept function provides an important principle for classifying manufactured objects. Can young children understand such concepts? Can they sort appearances from ‘deeper’ concepts? Our research suggests that they can, given adequate information, but some such concepts do not emerge until 4, 5, or even 6 years of age.