We present the typological approach to child language research. The typological approach places language diversity at the centre of acquisition research, thereby limiting arbitrary adjustments to theory and practice. We apply the typological approach to Ingram’s (2002) measures of whole-word phonological complexity (PMLU) and proximity (PWP). Our generalised PMLUg measure takes into account crosslinguistic variation in word status, including complex predicates and words without vowels. We analysed conversational data from Dutch, English, Japanese, Portuguese, Spanish, and Xi’iùy to determine whether two-year-old children target and produce words with significant between-language differences in phonological complexity. We found significant between-language differences in PMLUg for the target and produced words, but not PWPg. Comparing the complexity of the children’s words with the complexity of target words reveals their growth potentials along the syllable and consonant dimensions. Our study begins the cumulative investigation of the features that determine whole-word phonological complexity and proximity crosslinguistically.

Previous research in child language shows that many aspects of language acquisition are frequency-linked. This study tests whether input or usage frequency predicts the order of acquisition and accuracy of a bilingual Greek–English child's English possessives. The child was followed longitudinally from age 2;6 to 3;11. Order of acquisition was comparable to that of same-aged monolingual children. The child's usage frequency and order of acquisition were highly correlated with input frequency, while her accuracy was not. We argue that the child's already-acquired Greek possessives facilitated acquisition of English possessives, even though the child's English input and usage frequencies were lower than in monolingual English children.