Background: Previous research has elucidated the associations between children's language development and reading habits, and maternal education, communication style, gender and birth order. Research including maternal age and child temperament is more scarce. We studied the associations of all these factors with children's expressive vocabulary and reading habits. We also analysed the relationships of reading with expressive vocabulary, and effect sizes associated with frequent reading.
Methods: Questionnaires were completed by mothers of 1091 children aged 17-19 months visiting the Swedish Child Health Services. Expressive vocabulary was assessed by the Swedish Communication Screening at 18 months, a screening version of McArthur-Bates Communicative Development Inventories. Mother's perception of ability to communicate was measured by a scale constructed ad hoc from the International Child Development Programmes, a parent education curriculum. Bates' 'difficultness' scale was used to assess temperament.
Results: Good communication, low maternal age, female gender and frequent reading were significantly associated with expressive vocabulary. High maternal education, good communication, higher maternal age, female gender and being a first-born child were significantly associated with frequent reading. Reading at least 6 times/week added more than 0.3 SD in vocabulary regardless of gender and communication.
Conclusions: The findings support the importance of reading and communication quality to early language development. Knowledge of the relationship between children's vocabulary and book reading in a context of joint attention is both theoretically and practically valuable to speech and language pathologists, pre-school teachers, child health workers and other professionals.