Choosing to presuppose: strategic uses of presupposition triggers
This PhD project investigates the discourse structuring and managing properties of presupposition triggers. Specifically, the thesis is a theoretical and experimental investigation of what motivates speakers to presuppose as opposed to assert content, and how this decision influences the course of the subsequent discourse. This thesis is divided into three parts: (I) the negotiation of new content that is introduced by presuppositions versus assertions [experiment 1], (II) the communication of degrees of beliefs via factive presupposition triggers in contrast to uncertainty expressions and the bare assertion [experiments 2–5], and (III) the signalling of parallel information via additive pre-supposition triggers [experiments 6–7]. The first part of the thesis teases apart the distinction between presupposed/asserted and at-issue/not at-issue content by investigating whether (i) presupposed at-issue content is inaccessible or less accessible for interlocutors than asserted at-issue content, and (ii) in what way interlocutors address presupposed content in the subsequent discussion if the presupposed content is indeed less accessible. The experimental results suggest that, when material is relevant to the discourse question, it can be challenged directly by a subsequent speaker whether it is formally asserted or presupposed. However, expressing relevant material through presupposition rather than assertion may reduce the frequency of such challenges. Thus, a speaker-hearer model would have to include interlocutors’ expectations both about information packaging and about the overall discourse topic, in order to determine which content material may be discussed further. The second part of the thesis focuses on the factive presupposition trigger know and its discourse structuring properties. For this purpose, experiments [2–3] investigated the speakers’ motivations in choosing between uncertainty expressions such as think, believe or the factive verb know in co-operative versus uncooperative scenarios. The results of both experiments suggest that speakers’ choice of formulation is influenced by (i) how likely they estimate an event to be and (ii) strategic considerations relating to the communicative context in which they are working. More specifically, speakers uttered know more frequently and for lower degrees of belief in uncooperative settings than in cooperative settings. Experiments [4–5] explored whether the strategic use of know in the uncooperative setting has to do with its discourse structuring properties as a presupposition trigger: By presupposing content speakers assume or act as if the conveyed information was already shared knowledge and not up for debate. Thus, hearers might be more inclined to accept and accommodate presupposed content than asserted content. For this purpose, speakers’ production choices and hearers’ interpretations of know versus the bare assertion were assessed. The results suggest that presupposing might have an advantage over asserting when speakers want to avoid further discussion of a topic. However, there was no evidence that hearers consider the speakers’ strategies when assessing their degrees of belief, which may mean that speakers can employ these communicative strategies successfully, though this point requires further investigation. The third part of the thesis investigates the discourse managing properties of additive particles such as too, which are argued to presuppose a propositional alternative. If a suitable antecedent for the presupposition is present in the preceding dialogue, the production of too has been argued to be obligatory. Experiments [6–7] test (i) the potential obligatoriness and discursive functions of additives by manipulating the antecedents’ salience focusing on the factors Similarity and Turn Distance; and (ii) whether speakers would purposely violate the obligatoriness of too and with that avoid signalling similarity between what they and the antecedent speaker said in order to socially distance themselves from the antecedent speaker. Overall, the results of experiments [6–7] suggest that while the production of additives seems to depend on the antecedent’s salience, additive production was not as frequent as expected if additives were indeed obligatory. More specifically, participants were found to utter additives more frequently when their utterance’s content matched the content of a previously formulated utterance and when the matching utterance directly preceded their utterance. Furthermore, results of experiment  suggest that speakers deliberately drop the use of additives when wanting to diverge from an impolite speaker. This project sheds more light on the speakers’ motivation to presuppose rather than assert content and on the way their production choices influence the preceding dialogue and the hearers’ interpretation. Overall, the results suggest that the speakers’ choice to either assert or presuppose content depends on (i) what content is part of the common ground, and (ii) speakers’ communicative goals: specifically in whether or not they are being maximally informative and cooperative. The thesis draws parallels between the discursive properties of di↵erent kinds of presupposition triggers while at the same time also highlighting possible di↵erences between them, in particular between factive and additive presupposition triggers. By demonstrating the strategic use of presupposition triggers, this thesis informs theories on presupposition accommodation, the common ground, and communicative strategies in cooperative and uncooperative contexts.