Alan M. Leslie

One of the major developments of the second year of human life is the emergence of the ability to pretend. A child's knowledge of a real situation is apparently contradicted and distorted by pretense. If, as generally assumed, the child is just beginning to construct a system for internally representing such knowledge, why is this system of representation not undermined by its use in both comprehend ing and producing pretense? In this article I present a theoretical analysis of the representational mechanism underlying this ability. This mechanism extends the power of the infant's existing capacity for (primary) representation, creating a capacity for metarepresentation. It is this, developing toward the end of infancy, that underlies the child's new abilities to pretend and to understand pretense in others. There is a striking isomorphism between the three fundamental forms of pretend play and three crucial logical properties of mental stale expressions in language. This isomorphism points to a common underlying form of internal representation that is here called metarepresentation. A performance model, the decoupler, is outlined embodying ideas about how an infant might compute the complex function postulated to underlie pretend play. This model also reveals pretense as an early manifestation of the ability to understand mental states. Aspects of later preschool development, both normal and abnormal, are discussed in the light of the new model. This theory begins the task of characterizing the specific innate basis of our commonsense “theory of mind.”