Intelligence and executive functioning in adult age: Effects of sibship size and birth order

Sibship size, sibling cognitive sensitivity, and children's receptive vocabulary

OBJECTIVES

The aim of the current study was to examine the relationship between sibship size and children's vocabulary as a function of quality of sibling interactions. It was hypothesized that coming from a larger sibship (ie, 3+ children) would be related to lower receptive vocabulary in children. However, we expected this association to be moderated by the level of cognitive sensitivity shown by children's next-in-age older siblings.

METHODS

Data on 385 children (mean age = 3.15 years) and their next-in-age older siblings (mean age = 5.57 years) were collected and included demographic questionnaires, direct testing of children's receptive vocabulary, and videos of mother-child and sibling interactions. Sibling dyads were taped engaging in a cooperative building task and tapes were coded for the amount of cognitive sensitivity the older sibling exhibited toward the younger sibling.

RESULTS

Hierarchical regression analyses were conducted and showed an interaction between sibship size and sibling cognitive sensitivity in the prediction of children's receptive vocabulary; children exposed to large sibships whose next-in-age older sibling exhibited higher levels of cognitive sensitivity were less likely to show low vocabulary skills when compared with those children exposed to large sibships whose siblings showed lower levels of cognitive sensitivity.

CONCLUSIONS

Children who show sensitivity to the cognitive needs of their younger siblings provide a rich environment for language development. The negative impact of large sibships on language development is moderated by the presence of an older sibling who shows high cognitive sensitivity.

Big brothers and little sisters? Sex selection and birth order

Should you be allowed to choose the sex of your child? Even before the advent of modern reproductive technologies, people have expressed interest in producing a child of a specific sex, trying everything from herbal treatments to sexual positions that have been claimed to produce a male or female child. Modern technologies such as flow cytometry make this a realistic possibility but what might the consequences be? In India and China, a preference for male offspring has led (via abortion) to a significant sex-ratio imbalance in those populations. Do other countries express strong preferences for male or female offspring? This article will address the possible birth order implications. Will we live in a world of first-born boys and second-born girls?