The Development of Language in Twins: I. A Comparison of Twins and Single Children

in the Proceedings of the American Association for the Advancement of Science, reported the case of a pair of twin boys who were so retarded in speech that members of the family could not understand them.These children lived in Boston in 1860.According to the report of an aunt, who visited them frequently, they developed a twin language so unlike English that they could not be sent to school because no one could understand them.Observation of the occasional development of such a special language by twins, suggested the problem of research undertaken here.The twin situation is, from an environmental point of view, quite unlike that of single children and it seemed possible that this might be a factor of considerable significance in the development of language. 1From the Institute of Child Welfare, the University of Minnesota, The Development of Language in Twins, Part II, The Development of Twins: Their Resemblances and Differences will appear in a subsequent issue.This will include a discussion of the mental development of twins, and a comparison of the types of twins in intelligence, language development and certain physical traits.McCarthy's (13) investigation "The Language Development of the Preschool Child" provided an excellent basis for comparison.This study was completed in the summer of 1928 at the Institute of Child Welfare of the University of Minnesota.Dr. Mc-Carthy selected 140 children (20 at each 6 months age level from 18 to 54 months) on the basis of sex and socio-economic status.She visited them and recorded 50 consecutive responses made by each child while he played with a group of toys that she presented to stimulate speech.These data were than analyzed in four different ways: by mean length of response; according to the Piaget functional analysis; by the grammatical construction of the sentence; and a word analysis by parts of speech.In brief the results indicated the developmental changes with age in agreement with other studies, as well as sex differences in favor of the girls.Differences in favor of the upper occupational groups were indicated also in each method of analysis.In the foreword to this study Dr. John E. Anderson says "On the basis of the number of controls utilized in the selecting of subjects and the care and thoroughness with which the data are analyzed, this monograph stands out as one of the best studies 179