Effect of sex and dyad composition on speech and gesture development of singleton and twin children.

Children's early vocabulary shows sex differences - with boys having smaller vocabularies than age-comparable girls - a pattern that becomes evident in both singletons and twins. Twins also use fewer words than their singleton peers. However, we know relatively less about sex differences in early gesturing in singletons or twins, and also how singletons and twins might differ in their early gesture use. We examine the patterns of speech and gesture production of singleton and twin children, ages 0;10-to-3;4, during structured parent-child play. Boys and girls - singleton or twin - were similar in speech and gesture production, but singletons used a greater amount and diversity of speech and gestures than twins. There was no effect of twin dyad type (boy-boy, girl-girl, boy-girl) on either speech or gesture production. These results confirm earlier research showing close integration between gesture and speech in singletons in early language development, and further extend these patterns to twin children.