An analysis of mother-infant interaction during the preverbal period has revealed the importance of gaze in establishing the phatic channel and in the development of an intersubjectivity between them. Before the infant starts speaking there are behavioural indices of intersubjectivity - this enables complex tasks to be jointly accomplished. Seven stages in the ontogenesis of joint co-ordinated activity have been identified. It is argued that there is a continuity of function between these preverbal communicative actions and later verbal behaviour. The two theories providing the theoretical basis for this research are Speech Act Theory (Searle 1969) and Piaget's (1953, 1970) theory of cognitive development. Some modification of these theories has been necessary. / Thesis (Ph.D.)-University of Natal, 1977.