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ASSESSING INFANT VOCABULARY DEVELOPMENT USING A BRITISH CD1

Antonia Hamilton, Kim Plunkett and Graham Schafer

Experimental Psychology, South Parks Road, Oxford OX2 3UD, UK

Fenson et al (1994) presented a profile of vocabulary development for a sample of 67 1 English-speaking American infants in the age range 8-16 months based on a version of the MacArthur Communicative Development Inventory. This questionaire is made up of three sections. First is a ‘comprehension only’ section listing 28 stock phrases often used by parents. The second section is a vocubulary checklist of 396 word divided into 19 semantic categories (IO noun categories, sound effects, games and routines, action wor&, words about time, descriptive wora& pronouns, question words, prepositions and location, ana’ quantifiers). Parents were asked to judge whether their children understood and/or produced the items in the checklist. The final section asked parents to report their infant’s actions and gestures. Fenson et al. provide a detailed analysis of this questionnaire data, including developmental trends in language production and comprehension for the age range investigated. These data provide a valuable source of baseline information for evaluating infant’s development during the early stages of language acquisition.

In this poster, we report an parallel investigation of English-speaking British children using an adapted version of the MacArthur CDI. The British questionnaire differed from the American version in a number of important respects. Firstly, the British checklist excluded the initial and final sections on stock phrases and actions and gestures, so only a 396 item vocabulary checklist was used. Within this list, words peculiar to American English were replaced with the British equivalent. These include candy/sweet, cookie/biscuit, crib/cot, diaper/nappy and trash/rubbish. Several items were omitted from the British checklist, including all sound effect words, the child’s own and the babysitter’s name. However, the British checklist included 4 colour terms and several commonly used nouns (eg: stone, sitting room, shop, pasta, rabbit) so that the total number of items was the same as the American checklist.

The British questionnaires were distributed to parents, usually prior to an experimental session with their infant using the preferential looking task. Our sample includes over 400 infants in the age range 14 to 26 months. We analysed the data in a similar fashion to Fenson et al., i.e., providing observed and fitted logistic curves for developmental trends in production and comprehension vocabularies. The results are presented in 5 percentile groups (90th, 75th, 50th, 25th and 10th) as in Fenson et al. We also carried out an items analysis on 18 words for direct comparison with the developmental norms for specific items reported in the Fenson et al. computerised database.

The results revealed some surprising discrepancies with the Fenson et al. study. In particular, both comprehension and production scores in the British infants were much lower than their American counterparts. For example, at 16 months the median in comprehension for British infants is 101 words whereas for American infants it is about 200 words. In production, the median for British infants is 12 words compared to 40 for the American infants. The items analysis also yielded significant differences in vocabulary development. We explore various possible explanations for these difference between the American and English samples, including the structure of the questionnaire itself, the socio-economic status of the participants in the study, cross-cultural differences in attitudes to questionnaire completion and the relative linguistic precocity of American and British infants. In addition, we provide experimental evidence from preferential looking tasks which indicate that parental report offers an accurate assessment of infant’s early vocabulary development.

Fenson, L., Dale, P.S., Reznick, J.S., Bates, E., Thal, D. J. & Pethick, S. J. (1994) Variability in early communicative development. Monographs of the Society for Research in Child Development, Serial No. 242, Vol. 59, No. 5.