Heredity and Environment in Phoneme Articulation: Hereditary and Environmental Contributions to Articulation Proficiency.

Large twin samples and recent applications of multiple regression techniques to behavioral genetics methodology makes possible evaluation of genetic and environmental contributions to the articulation proficiency of individual phonemes. Factor analysis of the articulation scores from 256 MZ and DZ twins and 124 of their non-twin siblings (all children ranged from 2; 11 to 9; 8 years) were conducted to reduce a 50-item articulation test to a more manageable set of five articulation factors. The twins' factor scores were then analyzed using multiple regression procedures to determine the extent to which the individual factors resulted from genetic and/or environmental influences. The /r/ and /∫, t∫, dƺ/ factors were found to have strong genetic components, while the /l, j, w/ factor was found to be strongly influenced by environmental sources of variation.