Whose turn is it anyway? Same- and cross-person compound contributions in dialogue

Whose turn is it anyway? Same- and cross-person compound contributions in dialogue Christine Howes, Patrick G. T. Healey, Matthew Purver {chrizba, ph, mpurver}@eecs.qmul. ac.uk Queen Mary University of London Interaction, Media and Communication Research Group School of Electronic Engineering and Computer Science London E1 4NS, UK Abstract In natural conversation people sometimes build larger grammatical, semantic and pragmatic units out of mul- tiple turns or installments. The incremental and col- laborative character of these ‘compound contributions’ presents challenges for theories of natural language pro- cessing. Compounds produced over successive turns by one person have often been analysed in essentially the same way as compounds produced by multiple people. In some recent accounts this putative equivalence has been taken as evidence for the claim that within- and cross-person language processing are fundamentally in- terchangeable. However, in this paper we present an analysis of compound contributions in a corpus of or- dinary dialogues which shows that same- and cross- person compound contributions are constructed in dif- ferent ways and have diﬀerent semantic and pragmatic eﬀects on the organisation of dialogue. In particular, we show that they diﬀer in the pragmatic environments in which they occur and that they have diﬀerent conse- quences for subsequent turn-taking and interpretation. This asymmetry highlights the need for models of dia- logue that account for not just the inherent incremen- tality of dialogue, but the diﬀerent status of each con- tributor towards a turn-in-progress. Keywords: Dialogue; compound contributions. Introduction Compound contributions (CCs) – dialogue contributions that continue or complete an earlier contribution, see e.g. (1) – are the paradigm case of coordination in dialogue and constitute a critical test case for theories of natural language processing. (1) Daughter: Dad: Daughter: Oh here dad, a good way to get those corners out is to stick yer ﬁnger inside. well, that’s one way. [from Lerner (1991)] CCs are of interest to dialogue theorists because they provide evidence about how contributions can cohere with each other at multiple levels – syntactic, semantic and pragmatic (though of course they are not the only way). They also indicate the radical context-dependency of conversational contributions, which can, in general, be highly elliptical without disrupting the ﬂow of the dia- logue. CCs are a dramatic illustration of this: speakers must rely on the dynamics of the unfolding context (lin- guistic and extra-linguistic) in order to guarantee suc- cessful processing and production. Much of the work on CCs has studied cross-person cases, in diﬀerent disciplines and under a variety of dif- ferent names, including collaborative completions (Clark, 1996; Poesio and Rieser, 2010), co-constructions (Sacks, 1992), joint productions (Helasvuo, 2004), and split ut- terances (Purver et al., 2006). Linguistic studies show that grammatical constraints are respected across speaker and hearer (see e.g. Gre- goromichelaki et al., 2009). In Finnish (which has rich inﬂectional morphology), and Japanese (a verb-ﬁnal lan- guage), cross-person CCs within a single clause conform to the strict syntactic constraints of the language, de- spite the change in speaker (Helasvuo, 2004; Hayashi, From a psycholinguistic point of view, the phe- nomenon of CCs seems compatible with mechanistic ap- proaches as exempliﬁed by the Interactive Alignment model of Pickering and Garrod (2004), which claims that, all things being equal, it should be as easy to com- plete another’s sentence as one’s own. According to this model, speaker and listener ought to be interchangeable at any point. A similar stance is taken by the gram- matical framework of Dynamic Syntax (DS: Cann et al., 2005). In DS, parsing and production are taken to em- ploy the same mechanisms, leading to a prediction that CCs ought to be strikingly natural (Purver et al., 2006). From an organisational point of view, it has been claimed that turn-taking operates not on individual conversational participants, but on ‘parties’ (Schegloﬀ, 1995). For example, a couple talking to a third person may organise their turns as if they are one ‘party’, rather than two separate individuals. Lerner (1991) speculates, following Sacks (1992), that cross-person compound con- tributions can clarify the formation of such parties, as they reveal a relationship between syntactic mechanisms and social organisation. He claims that this provides evi- dence of one way in which syntax can be used to organise participants into “groups”. Because a sentence is obviously a prototypical instance of that thing which is done by a unit. Nor- mally, some single person. That then permits it – for those who have the wit to do it – to be a way that some non-apparent unit may be demonstrated to exist.