This monograph originated as an interim report on the research project Cog- nitive and Social Determinants on Language Acquisition which I conducted under the auspices of the German Department of the University of Frankfurt from September 1971 until the end of 1976. Since November 1972 this project was financed by the Max-Planck-Institut fur Bildungsforschung in Berlin as part of the research project Elternhaus und Schule conducted by Oevermann, Krappmann, and Kreppner. While the goal of this project on language acquisition is the reconstruc- tion of the language development of three German children: two middle-class children and one lower-class child from the time of the first linguistic utterances up to the fourth birthday, this interim report deals only with early language development, and it is essentially based on a large body of observational data on the language development of the two middle-class chil- dren from their 16th up to their 23rd months of life. In its German version this monograph was completed in March 1975 and pub- lished by Klett Verlag in the series "Konzepte der Humanwissenschaften".