Social cognition refers to that ability which makes it possible for one to infer another's covert, inner psychological experiences and to interact with that individual accordingly (Shantz 1975; Flavell 1977). Piaget (1926) maintains that the ability to decenter socially and to take into account the perspective of another develops gradually as the child interacts over time with more and more people in different situations. The result is that the child's speech is highly egocentric until the age of seven or eight. Vygotsky (1962), on the other hand, believes that speech is essentially social in nature at the beginning and that egocentric and social speech are interrelated, with egocentric speech having a social quality and social speech an egocentric potential. The purpose of this study is to compare the views of Piaget and Vygotsky on the development of communicative and egocentric speech in children and to consider their conclusions in light of spontaneous speech data of children 4-8 years old. After considering the strengths of the models offered by Piaget and Vygotsky, a model of the development and differentiation of egocentric and communicative speech is presented. The theoretical basis for the proposed model is discussed and illustrated with examples taken from the spontaneous speech samples collected. (Author/CLK)