Categorical Recurrence Analysis of Child Language

Categorical Recurrence Analysis of Child Language Rick Dale (rad28@cornell.edu) Michael J. Spivey (spivey@cornell.edu) Department of Psychology, Cornell University Ithaca, NY 14850 USA Abstract vocalization increase their quantity and quality. These timely caregiver interactions perhaps provide clues that, as grammar learning proceeds, there may also be a process of syntactic coordination. The strong assumption therefore has important theoretical consequences. Recently, Garrod and Pickering (2004) have argued that dialogue is such a fluid and seemingly simple task for us because it is steeped in coordination mechanisms found in many cognitive processes during social interaction. The coordination assumptions about language input during acquisition, both weak and strong versions, complement this discussion by pursuing the extent to which coordination occurs and changes at a syntactic level of description in child-caregiver interaction. Although the weak assumption can be corroborated easily by simple observation of child and caregiver, the strong version remains a tricky issue to quantify. For this reason, it is important to pursue novel means of analyzing child-directed and child-produced language. This paper presents an approach toward strong coordination by employing recurrence analysis, a technique used in a variety of disciplines. The analysis reveals global structural patterns of child and caregiver language alignment during interaction. By “global,” we mean drawing general quantitative measures, with minimal dependence on statistical assumptions, describing the extent to which a bout of child-caregiver interaction involves language structures that are more or less similar to each other. Doing so provides a quantification of syntactic coordination between interlocutors in transcripts of naturalistic dialogue. The method is based on analyzing ordered sequences of measurements, and can be extended easily to comparing how two ordered sequences of measurements involve patterns of recurrence. The ordered sequences of concern here, of course, are time series of syntactic class usage by child and caregiver. The approach therefore provides a window on how structures used by the child “recur” in those used by caregiver (and vice versa). The basic approach is given a technical introduction below, followed by two analyses of corpora drawn from the CHILDES database (MacWhinney, 2000). Coordination between conversation partners occurs at multiple levels, including choice of syntactic structure. A number of outstanding questions concerning the origin of this coordination require novel analytic techniques. Here we introduce and adapt a widely applied dynamical analysis, recurrence analysis. We use this method to explore lexical and syntactic coordination between children and caregivers in conversation. Results indicate that children and caregivers coordinate sequences of syntactic classes, and that this coordination diminishes over development. Introduction Quite a bit of research has been devoted to analyzing children’s developing language and the kind of input available for its acquisition. Recently, for example, some research has suggested that caregivers may issue contrastive responses to a child’s ungrammatical utterances, serving both to model how a structure should be used and as evidence that the child has erred (e.g., Chouinard & Clark, 2003). Accompanying this is the growing evidence that positive statistical information available in the input is sufficient to drive considerable generalization for learning grammatical structure (e.g., Lewis & Elman, 2001; Reali & Christiansen, 2003). All this research makes the broad and surely sensible assumption that the language use of children and caregivers is following a path of alignment or coordination: Statistical input and contingent responses in a conversation, if effective, shape the language of both the child and caregiver toward “syntactic coordination. ” This assumption has a strong and a weak interpretation. In the weak and clearly trivial version, coordination merely refers to the child coming to use the particular language spoken by the caregiver. In the strong version, it implies that within individual interactions there is a process of coordination taking place. The child (and/or parent) is inclined to produce sequences of syntactic classes, during a conversation, that match those being heard. Research on adult conversation has lately suggested that a wide variety of behavior is coordinated in this way during social interaction. For syntactic structures particularly, for example, Branigan, Pickering and Cleland (2000) recently demonstrated that, in a picture-description dialogue, participants often repeat syntactic structures employed by another member of the conversation (see Garrod & Pickering, 2004 for a review). Research on preverbal vocalization also suggests that coordination may be a crucial characteristic of the language-learning task. For example, Goldstein, King and West (2003) recently demonstrated experimentally that maternal responses contingent on infant Recurrence Analysis The past 20 years have seen a family of techniques emerge in the physical sciences that allows global analysis of time series produced by dynamical systems. Global dynamical analyses generate informative parameters concerning a time series and the process generating it. For example, computing the Lyapunov exponent from a time series of measurements (e.g., the weather) provides an indication of