When knowledge causes failure: Children's extension of novel adjectives and the interpretation of one

When studying language acquisition, the interaction of different modules (e.g. syntax, semantics, pragmatics) must be considered. In this case study we scrutinize a body of experimental work on adjectival acquisition and explore how this interaction affects the assessment of children's linguistic knowledge.Previous research indicates that 3-year-old children extend novel adjectives to objects within but not across the same basic-level category. However, Rulf (2004) argues that the pronoun one in the experimental prompt used is pragmatically odd in many of these studies (Waxman and Markow, 1998; Klibanoff and Waxman, 1999; Waxman and Klibanoff, 2000; Waxman and Booth, 2000). In the first experiment, we investigated how adults interpret the pronoun one. Our results strongly suggest that even adults would have failed the experimental task. In a second experiment with children, we eliminated the pragmatically odd pronoun usage and found that both 3- and 4-year olds were able to extend novel adjectives across categories. This suggests that previous task failure by 3-year olds was due not to a non-adult interpretation of adjectives, but to an adult-like interpretation of the pronoun. If so, previous studies have underestimated the grammar of these children, both with respect to adjectival interpretation and the interpretation of the pronoun one.