PURPOSE: to describe the phonological systems of monozygotic twins both having phonological disorders and to analyze the gradual development of the speech therapy after applying Modified Maximal Opposition Model in order to investigate the influence of genetic and environmental factors on the outset and continuity (maintenance) of phonological disorders. METHODS: the initial phonological assessments were compared as well as the target-sounds used in therapeutic plan, and the final phonological assessments at the end of each year of treatment for both monozygotic male twins who were six years and five months of age at the beginning of the research, and diagnosed as having phonological disorders. The boys were treated from August 2002 to December 2004 according to the Modified Maximal Opposition Model. All the material was obtained from the database of a project developed in the speech/language clinic of the Federal University of Santa Maria. RESULTS: great similarities were found in the phonological systems of both subjects in the beginning, during the therapeutic evolution and at the end of the phonological therapy, even though the target sounds were not necessarily the same throughout therapy. The boys acquired the absent and partially acquired sounds, presenting generalization in the various possible situations, confirming the efficiency of the therapeutic model employed. CONCLUSION: the genetic influence induces the onset and continuity of phonological disorders; nevertheless environmental factors cannot be disregarded.
Language; Speech; Twins; Language Development; Speech, Language and Hearing Sciences
