Why does parental language input style predict child language development? A twin study of gene–environment correlation

• DOI: 10.1016/j.jcomdis.2015.07.004
• Publication Date: 2015-08-04T16:45:16Z
• Authors: Philip S. Dale; Maria Grazia Tosto; Marianna E. Hayio...; Robert Plomin
• Keywords: Male; Parents; Linguistics and Language; Child language; Cognitive Neuroscience; 150; детский язык; Experimental and Cognitive Psychology; Language Development; Article; Speech and Hearing; Genetics; Twins, Dizygotic; Humans; 0501 psychology and cognitive sciences; Longitudinal Studies; Parent-Child Relations; Language; 4. Education; 05 social sciences; Input; Age Factors; Twins, Monozygotic; LPN and LVN; 400; генетика; Child, Preschool; Female; Gene-Environment Interaction; Child Language

There are well-established correlations between parental input style and child language development, which have typically been interpreted as evidence that the input style causes, or influences the rate of, changes in child language. We present evidence from a large twin study (TEDS; 8395 pairs for this report) that there are also likely to be both child-to-parent effects and shared genetic effects on parent and child. Self-reported parental language style at child age 3 and age 4 was aggregated into an 'informal language stimulation' factor and a 'corrective feedback' factor at each age; the former was positively correlated with child language concurrently and longitudinally at 3, 4, and 4.5 years, whereas the latter was weakly and negatively correlated. Both parental input factors were moderately heritable, as was child language. Longitudinal bivariate analysis showed that the correlation between the language stimulation factor and child language was significantly and moderately due to shared genes. There is some suggestive evidence from longitudinal phenotypic analysis that the prediction from parental language stimulation to child language includes both evocative and passive gene-environment correlation, with the latter playing a larger role.The reader will understand why correlations between parental language and rate of child language are by themselves ambiguous, and how twin studies can clarify the relationship. The reader will also understand that, based on the present study, at least two aspects of parental language style - informal language stimulation and corrective feedback - have substantial genetic influence, and that for informal language stimulation, a substantial portion of the prediction to child language represents the effect of shared genes on both parent and child. It will also be appreciated that these basic research findings do not imply that parental language input style is unimportant or that interventions cannot be effective.