Turn-boundary projection: Looking ahead

Turn-boundary projection: Looking ahead Marisa Tice (middyp@stanford.edu) Tania Henetz (thenetz@stanford.edu) Margaret Jacks Hall, Stanford University Stanford, CA 94305-2150 USA Jordan Hall, Stanford University Stanford, CA 94305-2150 USA Abstract 2006, but see Gravano & Hirschberg, 2011). Addressing turn projection experimentally, de Ruiter and colleagues (2006) asked Dutch speakers to listen to fragments of spontaneous speech and press a button at the moment they anticipated the speaker would be finished speaking. The stimuli were manip- ulated phonetically, controlling for potential projection cues such as intonation, lexicosyntactic information, and rhythm. Their results suggest that speakers rely primarily on lexical information (which also provides syntactic cues) to identify upcoming turn-end boundaries. Coordinating with others is hard; and yet we accomplish this every day when we take turns in a conversation. How do we do this? The present study introduces a new method of measuring turn-boundary projection that enables researchers to achieve more valid, flexible, and temporally informative data on online turn projection: tracking an observer’s gaze from the current speaker to the next speaker. In this preliminary investigation, participants consistently looked at the current speaker during their turn. Additionally, they looked to the next speaker before her turn began, and sometimes even before the current speaker finished speaking. This suggests that observer gaze is closely aligned with perceptual processes of turn-boundary projection, and thus may equip the field with the tools to explore how we manage to take turns. Keywords: Turn-taking; Social cognition; Eye tracking; Co- ordination; Timing; Conversation; Interaction The experimental approach introduced by de Ruiter et al. (2006) is an significant step forward in research on boundary projection, but there is still much to be addressed. Specifi- cally, we do not know how to account for boundary projec- tion as the turn is unfolding. Listeners have access to only that information which has already been spoken, and so their use of cues may differ over the course of a turn. For ex- ample, it could be the case that listeners track intonation as a primary cue to the beginning of a turn’s denouement, and then increase their reliance on lexical information to precisely identify the end of the upcoming syntactic clause. The infor- mation that listeners use to track upcoming turn boundaries should reflect their integrated knowledge of all the cues avail- able to them as the turn is unfolding. Introduction Interacting with others requires us to make a number of com- plex linguistic, social, and cognitive decisions. Despite this, most conversations proceed smoothly, allowing us to take for granted the intricate processes taking place in getting the tim- ing of our actions right on cue. Turn-taking during conversa- tion is one phenomenon that exemplifies these issues. Intu- itively we seem to wait for the current speaker to stop talk- ing before we start conjuring up a response, with each turn preceded and followed by orderly pauses or ‘gaps’ in speak- ing. But this is not the case: not only do we not ‘wait’, but there are often no gaps between speakers at all! Speakers are extremely adept at taking turns efficiently, averaging 0.2- 0.4 second gaps in face-to-face conversation (Brady, 1968; Stivers et al., 2009) and 0.7 second gaps over the phone (Jaffe & Feldstein, 1970), often with less than 5% overlap (Levinson, 1983). This general pattern has been observed across many cultures, leading researchers to conclude that in- terlocutors adhere to standards of no-gap-no-overlap in trans- ferring turns from one speaker to the next (de Ruiter et al., 2006; Sacks et al., 1974; Stivers et al., 2009). To accom- plish this no-gap-no-overlap timing, listeners must be able to actively project the end of the current speaker’s turn (here- after, turn-end boundary), while simultaneously starting to plan their response. The prevailing method of investigating how projection takes place is to use corpora to identify linguistic cues that co- incide with turn-end boundaries (e.g. prosodic, syntactic, and pragmatic boundaries; (Ford & Thompson, 1996; Caspers, 2003)). But these cues often co-occur, making it difficult to interpret relative cue importance. Additionally, some of these cues might come too late for listeners to make use of them, for instance, lengthening of the final word in an utter- ance happens nearly at the end of the turn (de Ruiter et al., The button-press methodology gives us a single point in the turn at which to test a manipulation. It is incapable of track- ing listeners’ ongoing certainty level about upcoming turn- end boundaries; especially in cases where there is a possible, or even probable, but not realized turn-end (e.g. “Did I ever tell you about my Aunt Millie? She was a wild one.”). In listening to this signal, participants in a button-press experi- ment are likely to enter their response after “Millie” or after “one.” In the case that they were not fooled by the first po- tential turn-end place, the single button press could not tell us about their ongoing projection: how close they came to thinking of it as a turn-end boundary, what cues were im- portant at the time, et cetera. The button-press also adds an “input” requirement to the task, which might be sensitive to the task instructions. An ideal measure of anticipation would not require explicit instructions, easing the cognitive load on participants that might arise from the specific task. We propose a new method of investigating turn-projection behavior: tracking observer gaze. In the utterance about Aunt Millie, gaze might reveal a robust effect of the initial proba- ble turn-end point: a gradient increase and then decrease in transition-related looks as the utterance continues. Button- pressing, in contrast, indicates the point in time when the ob- server felt they had sufficient evidence to respond to an utter-