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The present experiments investigate how young language learners begin to acquire form-based categories and the relationships between them. We investigated this question by exposing 12-month-olds to auditory structure of the form aX and bY (infants had to learn that a-elements grouped with Xs and not Ys). Infants were then tested on strings from their training language versus strings from the other language using a preferential-listening procedure. Importantly, the X and Y elements were new at test, requiring infants to generalize to novel pairings. We also manipulated the probability of encountering grammatical structures of the training language by mixing strings from two artificial languages according to 83/17 and 67/33 percentage ratios in Experiment 2. Experiment 1 shows that 12-month-olds are capable of forming categories of X- and Y-elements based on a shared feature and, furthermore, form associations between particular a- and b-elements and these categories. Experiment 2 shows that learning was sustained even when 17% of instances from another language were present during training. However, infants failed to generalize when exposed to a larger percentage of strings from another language. The findings demonstrate that the first step of form-based category abstraction (the ability to generalize based on marker-feature pairings) is in place by 12 months of age.

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It has been claimed that in the language systems of people with Williams syndrome (WS), syntax is intact but lexical memory is impaired. Evidence has come from past tense elicitation tasks with a small number of participants where individuals with WS are said to have a speci c de cit in forming irregular past tenses. However, typically developing children also show poorer performance on irregulars than regulars in these tasks, and one of the central features of WS language development is that it is delayed. We compared the performance of 21 participants with WS on two past tense elicitation tasks with that of four typically developing control groups, at ages 6, 8, 10, and adult. When verbal mental age was controlled for, participants in the WS group displayed no selective de cit in irregular past tense performance. However, there was evidence for lower levels of generalisation to novel strings. This is consistent with the hypothesis that the WS language system is delayed because it has developed under different constraints, constraints that perhaps include atypical phonological representations. TheRequests for reprints should be addressed to Michael Thomas or Annette Karmiloff-Smith, Neurocognitive Development Unit, Institute of Child Health, 30, Guilford Street, London WC1N 1EH, UK. Email: M. Thomas@ich.ucl.ac.uk or a.karmiloff-smith@ich.ucl.ac.uk We would like to express our appreciation to the Williams Syndrome Foundation, UK, for their generous help in putting us in touch with families whom we warmly thank for their participation in this research. Thanks also to Dorothy Bishop and Marc Joanisse for helpful comments on an earlier draft on this paper. This research was supported by MRC Programme Grant No. G9715642 to Annette Karmiloff-Smith. results are discussed in relation to dual-mechanism and connectionist computational models of language development, and to the possible differential weight given to phonology versus semantics in WS development .

When people describe motion events, their path expressions are biased toward inclusion of goal paths (e.g., into the house) and omission of source paths (e.g., out of the house). In this paper, we explored whether this asymmetry has its origins in people's non-linguistic representations of events. In three experiments, 4-year-old children and adults described or remembered manner of motion events that represented animate ⁄ intentional and physical events. The results suggest that the linguistic asymmetry between goals and sources is not fully rooted in non-linguistic event representations: linguistic descriptions showed the goal bias for both kinds of events, whereas non-linguistic memory for events showed the goal bias only for events involving animate, goal-directed motion. The findings are discussed in terms of the mapping between non-linguistic representations of goals and sources in language, focusing on the role that linguistic principles play in producing a more absolute goal bias from more gradient non-linguistic representations of paths.