Bilingual vocabulary acquisition between ages 12 and 24 months: a case study

Abstract

This dissertation is on the subject of bilingual vocabulary acquisition, specifically regarding children between the age of 12 and 20-24 months, and presents a longitudinal case study of a Cantonese-English bilingual child.

We begin by questioning the role of exposure (in terms of number and frequency of utterances) as a reliable indicator of vocabulary acquisition at such a young age. While exposure is undoubtedly a good indicator of acquisition from age 2;0 upwards (Huttenlocher, Haight, Byrk, Seltzer, & Lyons, 1991, David & Li, 2008), we suggest that other more specific factors are more crucial at earlier stages, when the rate of vocabulary growth is slower. As such, using a parental diary and a series of video experiments, we propose and test hypotheses concerning the roles of child directed speech (CDS), salience of exposure, emotional arousal and phonological complexity in early language acquisition.

Regarding CDS, results taken from the parental diary show apparent selection and adaptation of vocabulary to fit reduplicated forms between the ages of 1;0 and 1;5. In conjunction with previous research, we propose that, between 1;0 and 1;5, during the whole-word stage (Vihman & Croft, 2007), salience and phonological simplicity of exposure are key factors in vocabulary acquisition. This hypothesis points to a likely initial Cantonese dominance in English-Cantonese bilinguals, which is supported by our data.

Our results from video experiments appear to support hypotheses concerning positive emotional arousal as a facilitator of vocabulary acquisition prior to 20-24 months, and also of a child’s ability to acquire language with minimal exposure, in a similar but not identical process to fast mapping (Carey & Bartlett, 1978). We propose as such that emotional arousal is a key component in language acquisition before age 2;0, and link this type acquisition to flashbulb memories (Brown & Kulik, 1977).

Finally we show that our parental diary data corroborates the well documented verb and noun biases in Chinese (Choi & Gopnik, 1995) and English (Bornstein et al., 2004) respectively. We question what these conflicting biases may mean for a bilingual child in terms of language dominance and code mixing, and also discuss potential reasons for, and implications of, these biases.