Publications

Abstract

Language processing is rapidly incremental, but evidence bearing upon this assumption comes from very few languages. In this paper we report on a study of incremental processing in Murrinhpatha, a polysynthetic Australian language, which expresses complex sentence-level meanings in a single verb, the full meaning of which is not clear until the final morph. Forty native Murrinhpatha speakers participated in a visual world eyetracking experiment in which they viewed two complex scenes as they heard a verb describing one of the scenes. The scenes were selected so that the verb describing the target scene had either no overlap with a possible description of the competitor image, or overlapped from the start (onset overlap) or at the end of the verb (rhyme overlap). The results showed that, despite meaning only being clear at the end of the verb, Murrinhpatha speakers made incremental predictions that differed across conditions. The findings demonstrate that processing in polysynthetic languages is rapid and incremental, yet unlike in commonly studied languages like English, speakers make parsing predictions based on information associated with bound morphs rather than discrete words.

Abstract

A long-standing question in language development concerns the nature of the relationship between early lexical and grammatical knowledge. The very strong correlation between the two has led some to argue that lexical and grammatical knowledge may be inseparable, consistent with psycholinguistic theories that eschew a distinction between the two systems. However, little research has explicitly examined whether early lexical and grammatical knowledge are statistically separable. Moreover, there are two under-appreciated methodological challenges in such research. First, the relationship between lexical and grammatical knowledge may change during development. Second, non-linear mappings between true and observed scores on scales of lexical and grammatical knowledge could lead to spurious multidimensionality. In the present study, we overcome these challenges by using vocabulary and grammar data from several developmental time points and a statistical method robust to such non-linear mappings. In Study 1, we examined item-level vocabulary and grammar data from two American English samples from a large online repository of data from studies employing a commonly used language development scale. We found clear evidence that vocabulary and grammar were separable by two years of age. In Study 2, we combined data from two longitudinal studies of language acquisition that used the same scale (at 18/19, 21, 24 and 30 months) and found evidence that vocabulary and grammar were, under some conditions, separable by 18 months. Results indicate that, while there is clearly a very strong relationship between vocabulary and grammar knowledge in early language development, the two are separable. Implications for the mechanisms underlying language development are discussed.