Poster #77 - Genetic and Environmental Links Between Language and School Readiness

• In Event: Poster Session 15

Abstract

The development of language comprehension and expression are primary tasks of early childhood (Bates et al., 1995). Both expressive vocabulary and receptive vocabulary are positively related to school readiness (SR) (Fiorentino & Howe, 2004; Tabors et al., 2001). Behavioral genetic studies have found significant genetic and shared environmental (i.e., family-wide environmental influences shared among family members) effects on all 3 constructs, and the correlation between expressive vocabulary and school readiness is explained entirely by environmental factors (Forget-Dubois et al., 2009), but the relation between receptive vocabulary and school readiness has not been studied. The current study examines associations between school readiness and receptive vocabulary and two aspects of expressive vocabulary—vocabulary size and the average length of phrase. We explored whether receptive and expressive vocabulary uniquely predicted school readiness and the extent to which the links between language and school readiness are genetically and environmentally mediated.
Methods. The sample included 308 same-sex twin pairs (MZ = 122, DZ = 186) from the Boston University Twin Project who were assessed within one month of their 3rd birthdays. Observational measures of receptive vocabulary were collected using NIH Toolbox Picture Vocabulary Test (PVT; Gershon et al., 2013). Expressive language was assessed via parent report on the Language Development Survey (Rescorla, 1989) which provided measures of vocabulary size (CBCL_VOC) and the average length of phrase (CBCL_ALP). SR was assessed with the Bracken School Readiness Assessment (Bracken, 2007).
Results. All three variables were significantly correlated (Table 1); however, multiple regression analysis indicated that only CBCL_ALP and PVT uniquely predicted SR. Therefore, we did not include CBCL_VOC in subsequent analyses. Cholesky trivariate models were fitted to the data to estimate genetic and environmental influences on the two language measures and school readiness, and to explore sources of covariance between the three constructs. SR was entered last to examine genetic and environmental influences on SR independent of language (Figure 1). There were significant genetic (h2) and shared environmental (c2) variances for all variables (CBCL_ALP: h2=.19, c2=.70; PVT: h2=.27, c2=.15; SR: h2=.31, c2=.39). The remaining variances were due to nonshared environments (i.e., environmental influences that are unique to individuals within a family).
There were no common genetic effects between the two language measures. Only receptive language (PVT) was genetically linked with SR. There were no significant genetic influences on SR independent of PVT. There was a common shared environmental factor linking both language dimensions and SR; however, there were also shared environmental influences unique to SR.
Discussion. Language is related to school readiness in preschoolers and this association is primarily due to shared environmental effects. Thus, the family-wide influences that promote language development also contribute to basic skills in other areas such as school readiness. Socioeconomic status and parenting are two possible sources of shared environmental influences common to language and school readiness. The two language measures were genetically distinct which is consistent with research suggesting different biological processes underlie receptive and expressive language.

Authors

• Yue Ma, Boston University
  Presenting Author

• Jody M. Ganiban, George Washington University

• Kimberly J Saudino, Boston University