Tracking Lexical and Syntactic Alignment in Conversation

Tracking Lexical and Syntactic Alignment in Conversation Christine Howes, Patrick G. T. Healey and Matthew Purver {chrizba,ph,mpurver}@dcs.qmul. ac.uk Queen Mary University of London Interaction, Media and Communication Group Mile End Road, London E1 4NS Abstract As much empirical work attests, people have a reli- able tendency to match their conversational partner’s body movements, speech style, and patterns of language use – amongst other things. A specific version of this tendency, Structural priming, which occurs when prior exposure to a particular linguistic structure facilitates one’s subsequent processing of the same structure, has gained widespread acceptance. Pickering and Garrod (2004) propose that cross-person structural priming is a basic mechanism of conversational coordination – part of an automatic, resource-free alignment mechanism that is the basis for all successful human interaction. We present evidence to the contrary from two analyses of a corpus of ordinary conversation. The first suggests that the level of structural (syntactic) matching is no dif- ferent from chance, and the second that the observed statistical correlation between prime form and target form may be entirely associated with repetition of lexical form. Keywords: structural priming; alignment Introduction The apparent tendency for speakers to repeat their own or others syntactic or structural choices in conversation – a phenomenon referred to as structural or syntactic alignment – has been a subject of particular scrutiny (see Pickering and Ferreira (2008) for an overview). The evidence for such alignment in dialogue comes from two main sources: experimental studies of task- oriented dialogue (e.g. (Branigan, Pickering, & Cleland, 2000)), and corpus studies that track frequency of use of these same constructions in language use outside of the laboratory setting (e.g. (Gries, 2005)). In the basic experimental set-up of Branigan and col- leagues, there are two participants, one of whom is a confederate of the experimenter. The participants de- scribe picture cards to each other, the critical items of which require the use of ditransitive verbs in their de- scriptions. In English, there are two syntactic struc- tures which can be used; one a double object structure (“The thief giving the nurse the banana”), and the other using a preposition (“The thief giving the banana to the nurse”). The confederate uses a scripted descrip- tion of the ditransitive prime sentences, thus manipu- lating which type naive subjects are exposed to. Par- ticipants are more likely to use the type of structure that they have just used or been exposed to. This has been found to hold across comprehension and production (Branigan, Pickering, Stewart, & McLean, 2000; Bock, Dell, Chang, & Onishi, 2007), from main clauses to rel- ative clauses (Branigan, Pickering, McLean, & Stewart, 2006) and even across languages in bilingual speakers (Hartsuiker, Pickering, & Veltkamp, 2004). Different factors found to increase the strength of syntactic align- ment include the distance between the prime and the target, participant role (Branigan, Pickering, McLean, & Cleland, 2007) and, importantly for the interactive alignment model (see below), reuse of the same or se- mantically related lexical items (Branigan, Pickering, & Cleland, 2000). In a corpus study using the International Corpus of English (ICE-GB), Gries (2005) looked at the same syn- tactic alternation. His data show that there is a tendency to reuse the form of a ditransitive verb most recently en- countered (double object or prepositional), in line with the experimental results. Similar results have been found to hold with different constructions such as particle placement of phrasal verbs (Gries, 2005), future markers (“will” versus “going to”) and comparatives (“cleverer” versus “more clever than”) (Szmrecsanyi, 2005). Pickering and Garrod (2004) argue, in their Interac- tive Alignment model, that alignment is the basis for successful communication; “successful dialogue occurs when interlocutors construct similar situation models to each other” (Pickering & Garrod, 2006, p206). In or- der to do this, interlocutors align on situation models; however, as this alignment is not usually negotiated ex- plicitly, it is hypothesised to arise automatically from local alignment, via resource-free priming mechanisms. 1 Alignment at local levels, including lexical (repetition of words) and the syntactic alignment discussed above, “percolates”, leading to alignment at other levels. From priming to alignment? There are three problems with using these studies to support the claim that cross-speaker structural priming is ubiquitous in conversation. First, automatic priming predicts an increase in matching of all structures across turns, but this claim has not been directly tested. For practical reasons, experimental studies have focussed on situations in which specific syntactic alternatives can be used to describe the same situation. Similarly, corpus studies have tended to track the frequency of use of spe- Note that the observed effects are alignment effects; priming mechanisms are their hypothesised cause, leading to two distinct questions – does such alignment occur; and if it does, is it caused by priming?