Early vocabulary development: Relationships with prelinguistic skills and early social-emotional/behavioral problems and competencies.

The aim of this longitudinal study was to investigate early vocabulary development and its relationships with prelinguistic communication skills and social-emotional/behavioral (SEB) problems and competencies. The participants were 58 healthy Finnish-speaking children (30 girls, 28 boys). First, the concurrent relationships were investigated at the age of 18 months. Second, the relationships between prelinguistic communication skills and SEB problems and competencies at 18 months, and subsequent vocabulary scores at 24 and 30 months, were examined. Parental reports on early vocabulary (MacArthur Communicative Developmental Inventories; MCDI), prelinguistic communication skills (The Infant-Toddler Checklist of the Communication and Symbolic Behavior Scales Developmental Profile; ITC), SEB problems and competencies (Brief Infant-Toddler Social and Emotional Assessment; BITSEA) were gathered. Compared to boys, girls scored significantly higher on ITC Speech Composite at 18 months and expressive vocabulary measures at 18, 24, and 30 months. Vocabulary, as well as prelinguistic communication measures, correlated with SEB competencies at 18 months. Furthermore, vocabulary, as well as ITC Symbolic Composite and Total Score, correlated negatively with externalizing problem and SEB Total Problem scores. With regard to subsequent vocabulary development, all of the prelinguistic communication measures at 18 months correlated with vocabulary at 24 and 30 months. However, when accounted for gender and earlier vocabulary, only the associations with ITC Speech Composite and Total Score at 24 months remained significant. SEB Competencies at 18 months correlated positively, while externalizing problems at 18 months correlated negatively with vocabulary at 24 and 30 months, however, these associations did not remain significant, when accounted for gender and earlier vocabulary.