1.   Introduction

There were existed variation in language development between children and factors related to child and family could facilitate or inhibit language development. Language development is affected by some structural factors like gender and some socioeconomic factors like parent’s education and job. Previous studies revealed that gender, parent’s education and job associated with individual differences in language development but it is unknown which language components (i.e. semantic, syntax or articulation of words) is more influenced by these factors. Another factor that may related with language development is sibling effect. There was controversy about the role of siblings in language development. Some theories, including the resource dilution hypothesis (Downey, 2001) and the confluence model (Jæger, 2009), have been proposed for explaining how the number of siblings may be related to language development. Another family-related factor that could explain individual differences in language development is parenting styles. The role of parenting style is more investigated as a predictor of academic achievement among school-age children, but little is known about the role of different parenting styles, including authoritative, authoritarian, and permissive parenting styles, in linguistic development components, including semantic, syntax, and word articulation.

This study aimed to investigate the influence of child gender, fathers and mother's education, and job, the number of siblings, and parenting styles on language development components (semantics, syntax, and word articulation).

2. Methodology

 The populations were normal preschool children and their parents in Karaj, Iran. Participants were 98 children and their parents, which were selected by a convenient method. Test of language development (3 edition) administered on children and parents asked for a response to demographic questionnaire and Parenting authority questionnaire.

3.                   Results

Results showed that girls compared with boys had better syntactic understanding, grammatical completion, and relational vocabulary. There were no significant differences between families with different numbers of siblings. Father's job did not influence children's language performance, whereas the mother's job had a positive influence on the components of language development. Father and mother's educational level positively affected syntactic understanding, grammatical completion, and relational vocabulary.

Furthermore, authoritative and permissive parenting styles could positively predict semantic and syntax development, whereas authoritarian parenting styles could negatively predict semantic and syntax outcomes. Therefore it could argue that parental socioeconomic status (especially parent's educational level and mother employment) and parenting styles could influence language acquisition in semantic and syntax domains. Moreover, girls outperformed boys in semantic and syntax in the preschool period.

4. Discussion

This study showed that social and family-related factors more influence some aspects of language development. These components consisted of the ability to use relational vocabulary, syntactical understanding, and morphological completion. The ability to use relational vocabulary is characterized by distinguishing similarities and differences between words, understanding different concepts, and the relationship between ideas. As the findings of this study showed, the development of this language component was facilitated when parents had higher educational levels and more used authoritative parenting styles. In sum, some of the contribution that this study added to literature could be as follows: (1) Girls compared to boys had better linguistic skills in semantic and syntax domain; (2) mother’s education and job and father’s education is associated with morphological completion skill and the ability to use relational vocabulary. The children whose mothers had a job out of the home had a better score in semantic and syntax development; (3) the number of siblings does not affect the linguistic development in different domains. (4) Authoritative parenting styles, more than other parenting styles, positively affect the development of relational vocabulary, syntactic understanding, and morphological completion.

5.Conclusion

According to the findings of this study, environmental facilitation for language development, for children from families in which the mother’s job is the only household and had low education level, is better to focus on the relational vocabulary, syntax understanding, and morphological completion. It is better in a future study with a mediational model to investigate the factors which may mediate the relationship between parenting styles and language development among preschool children.