Variation in Vocabulary Development as a Function of Birth Order

Abstract

Several researchers have argued for birth-order differences in the rate and style of children's early vocabulary development. However, the results of those studies that have examined these issues directly have so far proved inconclusive. In the present study, an attempt was made to examine the question of birth-order differences in children's early vocabulary development by comparing the composition and age of acquisition of the first 50 and 100 words of 9 firstborns and their younger siblings using a longitudinal maternal diary methodology. A small but significant birth-order effect was found for the age at which the 50-word milestone was reached. However, there was no significant difference in age at 100 words, and there was a strong correlation between sibling pairs on both of these measures. As regards qualitative differences, second-borns had a significantly higher percentage of frozen phrases in their first 100 words and a significantly higher percentage of deictic personal pronouns in their first 50 and 100 words. However, no differences were found in the percentage of common nouns at either measurement point. It is argued that, on balance, these results are more consistent with a “different” than a “disadvantaged” view of later-borns' early language, and that those differences that do exist may be due, at least in part, to the occurrence of a higher degree of observational learning in second-borns' early language acquisition.