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Speech planning is a sophisticated process. In dialog, it regularly starts in overlap with an incoming turn by a conversation partner. We show that planning spoken responses in overlap with incoming turns is associated with higher processing load than planning in silence. In a dialogic experiment, participants took turns with a confederate describing lists of objects. The confederate’s utterances (to which participants responded) were pre-recorded and varied in whether they ended in a verb or an object noun and whether this ending was predictable or not. We found that response planning in overlap with sentence-final verbs evokes larger task-evoked pupillary responses, while end predictability had no effect. This finding indicates that planning in overlap leads to higher processing load for next speakers in dialog and that next speakers do not proactively modulate the time course of their response planning based on their predictions of turn endings. The turn-taking system exerts pressure on the language processing system by pushing speakers to plan in overlap despite the ensuing increase in processing load.

In conversation, speakers need to plan and comprehend language in parallel in order to meet the tight timing constraints of turn taking. Given that language comprehension and speech production planning both require cognitive resources and engage overlapping neural circuits, these two tasks may interfere with one another in dialogue situations. Interference effects have been reported on a number of linguistic processing levels, including lexicosemantics. This paper reports a study on semantic processing efficiency during language comprehension in overlap with speech planning, where participants responded verbally to questions containing semantic illusions. Participants rejected a smaller proportion of the illusions when planning their response in overlap with the illusory word than when planning their response after the end of the question. The obtained results indicate that speech planning interferes with language comprehension in dialogue situations, leading to reduced semantic processing of the incoming turn. Potential explanatory processing accounts are discussed.

When humans have a conversation with one-another, they generally take turns speaking one after the other without overlapping each others talk or leaving silence between turns for long stretches of time. Previous research has shown that conversation is a structured practice following rules that help interlocutors to manage the flow of conversation interactively. While at the beginning of a conversation it remains open who will speak when about what and for how long, interlocutors regulate the flow of conversation as it unfolds. One basic set of rules that interlocutors operate with governs the allocation of speaking turns, with the central rule stating that whoever starts speaking first at a point in time when speaker change becomes relevant has the rights and obligations to produce the next turn. The organization of turn allocation, therefore, is one reason for conversational turn taking to be so remarkably fast, with the beginnings of turns most often being quite accurately aligned with the ends of the previous turns. Observations of this outstanding speed of turn taking gave rise to a number of questions concerning language processing in conversational situations. The studies presented in this thesis investigate some of these questions from the perspective of the current listener preparing to be the next speaker who will respond to the current turn. The study presented in Chapter 2 investigates when next speakers begin to plan their own turn with respect to two points in time, (i) the moment when the incoming turn’s message becomes clear enough to make response planning possible and (ii) the moment when the incoming turn terminates. Results of previous studies were inconclusive about the timing of language planning in conversation, with evidence in favour of both late and early response planning. Furthermore, previous studies presented both evidence as well as counter evidence indicating that response planning depends or does not depend on an accurate prediction of the timing of the incoming turn’s end. The study presented here makes use of a novel experimental paradigm which includes a dialogic task that participants need to fulfil in response to critical utterances by a confederate. These critical utterances were structured, on the one hand, so that their message became clear either only at the end of the turn or before the end of the turn, and, on the other hand, so that it was either predictable or not predictable when exactly the turn would end. Participant’s eye-movements as well as their response latencies indicated that they always planned their next turn as early as possible, irrespective of the predictability of the incoming turn’s end. The presented results provide evidence in favour of models of turn taking that predict speech planning to happen in overlap with the incoming turn. Having established that next speakers begin to plan their turn in overlap, the study presented in Chapter 3 goes more into detail investigating to which depth language planning progresses while the incoming turn is still unfolding. To this end, a number of psycholinguistic paradigms were combined. In the study’s main experiment, participants had to fulfil a switch-task in which they switched from picture naming in response to an auditorily presented question to making a lexical decision. By manipulating the relatedness of the word for lexical decision with the picture that was prepared to be named before the task-switch it was possible to draw inferences on which processing stages were entered during the speech production process in overlap with the incoming turn. Participants’ behavioural responses in the lexical decision task revealed that they entered the stage of phonological encoding while the incoming turn was still unfolding, showing that planning in overlap is not limited to conceptual preparation but includes all sub-processes of formulation. Given that speech production regularly enters the stages of formulation in overlap with the incoming turn, as shown in Chapters 2 and 3, the question arises whether planning the next turn in overlap is cognitively more demanding than during the gap between turns. This question is approached in the study presented in Chapter 4 by measuring pupillometric responses of participants in a dialogic task. An increase in pupil diameter during a cognitive task is indicative of increased processing load, and pupillometric responses to planning in overlap with the incoming turn were found to be greater than responses to planning in the gap between turns. These results show that planning in overlap is more demanding than planning during the gap, even though it is highly practiced by speakers. After Chapters 2 to 4 investigated the timing and mechanisms of speech planning in conversation, Chapter 5 turns towards the timing of articulation of a planned turn, asking the question what sources of information next speakers use to time the articulation of a planned utterance to start closely after the incoming turn comes to an end. In this Chapter’s study, participants taking turns with a confederate responded to utterances containing or not containing different cues to the location of the incoming turn’s end. Participants made use of lexical and turn-final intonational cues, but not of turn-initial intonational cues, responding faster when the relevant cues were present than when they were not present. These results show that the timing of turn initiation in next speakers depends on the recognition of the incoming turn’s point of completion and not merely on the progress in planning the next turn. All evidence presented in Chapters 2 to 5 is summed up and bundled together in a cognitive model of turn taking, which is being presented in Chapter 6. This model assumes, centrally, that the planning of a turn and the timing of its articulation are separate cognitive processes that run in parallel in any next speaker during conversation. Planning generally starts as early as possible, often in overlap with the incoming turn, while the timing of articulation depends on the next speaker’s level of certainty that speaker change has become relevant at a particular moment, with a number of cues to the end of the incoming turn leading to an increase of certainty. Next turns are assumed to often be planned down to fully formulated utterance plans including their phonological form as early as possible on the basis of anticipations of the incoming turn’s message, which are created with the help of the general and situational knowledge about the world, the current speaker and her intentions, as well as the input that has been received so far. The level of certainty that speaker change becomes relevant rises or decreases as lexico-syntactic, prosodic, and pragmatic projections about the development of the current turn are fulfilled or not fulfilled. As the incoming turn progresses towards its end as was projected by the current listener, he becomes certain that speaker change becomes relevant and will initiate articulation of the prepared next turn. Viewing these two processes, planning a next turn and timing of its articulation, as separate makes it possible to explain the observable fast timing of turn taking while still modelling the allocation of turns as interactionally managed by interlocutors — a considerable advantage of the presented model compared to more traditional perspectives on turn taking and conversation.

This special issue investigates early responses—responsive actions that (start to) unfold while the production of the responded-to turn and action is still under way. Although timing in human conduct has gained intense interest in research, the early production of responsive actions has so far largely remained unexplored. But what makes early responses possible? What do such responses tell us about the complex interplay between syntax, prosody, and embodied conduct? And what sorts of actions do participants accomplish by means of such early responses? By addressing these questions, the special issue seeks to offer new advances in the systematic analysis of temporal organization in interaction, contributing to broader discussions in the language and cognitive sciences as to the social coordination of human conduct.

Despite the importance of the agent role for language grammar and processing, its definition and features are still controversially discussed in the literature on semantic roles. Moreover, diagnostic tests to dissociate agentive from non-agentive roles are typically applied with qualitative introspection data. We investigated whether quantitative acceptability ratings obtained with a well-established agentivity test, the DO-cleft, provide evidence for the feature-based prototype account of (Dowty, David R. 1991. Thematic protoroles and argument selction. Language 67(3). 547-619) postulating that agentivity increases with the number of agentive features that a role subsumes. We used four different intransitive verb classes in German and collected acceptability judgements from non-expert native speakers of German. Our results show that sentence acceptability increases linearly with the number of agentive features and, hence, agentivity. Moreover, our findings confirm that sentience belongs to the group of proto-agent features. In summary, this suggests that a multidimensional account including a specific mechanism for role prototypicality (feature accumulation) successfully captures gradient acceptability clines. Quantitative acceptability estimates are a meaningful addition to linguistic theorizing.