The development of discourse markers is commonly believed to be a language-internal process. In this chapter it is demonstrated, however, that new discourse markers quite commonly also arise in situations of language contact. A range of borrowing processes are discussed, showing in particular that the borrowing process may extend across countries and continents. The Spanish discourse marker entonces "then, therefore, thus," for example, spread from Europe to Central and South America, Africa, and the Pacific Ocean area.

This chapter summarizes the findings presented in the book. As demonstrated in the preceding chapters, the rise of discourse markers is the result of a more complex process involving two separate mechanisms, namely grammaticalization and cooptation. It is argued that the framework used in the book offers an explanation of why discourse markers have the grammatical properties they do.

In this chapter, the framework proposed in Chapter 2 is applied to the history of Japanese. The discourse markers studied are dakedo, demo, douride, ga, jijitsu, sate, and wake. The findings presented are in support of the hypothesis proposed in Section 1.5, according to which discourse markers are the joint product of two separate mechanisms, with each of the mechanisms accounting for specific properties of discourse markers.

Chapter 6 presents a case-study of response markers and introduces a syntactic analysis within the framework of the Interactional Spine Hypothesis. Response markers are units of language which are used to respond to previous moves. I show that the target of confirmation can differ depending on the syntactic context. Response markers show the same pattern of multi-functionality as confirmationals do, providing evidence that there is a system in place which regulates both types of units of language. I compare my analysis to previous analyses of response markers and show that none of them are adequate because they restrict their attention to response markers used as answers to polar questions. This is, however, only one use of response markers: they can also be used to express agreement, acknowledge the addressee’s belief, or simply indicate that the responder is listening. The interactional spine predicts precisely these functions. I further show that response markers can be modified prosodically to express all kinds of emotional content and I develop an analysis for this pattern.

Chapter 2 reviews the state of the art of current attempts to syntacticize speech acts. These attempts are mostly based on classical speech act theory as developed by Austin and Searle in the sixties. It presents a brief overview of classic speech act theory. It identifies the issues pertaining to the relation between sentence structure and speech act type, which sets the stage for introducing the idea that speech act structure itself is part of syntax. I discuss the various stages and guises of this idea starting with Ross’s performative hypothesis and reviewing reanalyses of the idea within current syntactic theory. I then argue that all existing approaches toward the syntacticization of speech acts suffer from several weaknesses: specifically, most analyses fail to consider advances that have been made since classic speech act theory, namely the focus on the dynamic and interactional component of utterances.

Chapter 4 introduces the core of the proposal, namely the Interactional Spine Hypothesis, which provides a framework within which to analyze interactional language. The chapter begins by introducing the empirical phenomena to be addressed, namely confirmationals and response markers, and further introduces the analytical, theoretical, and methodological problems raised by these forms of interactional language. It show how the universal spine, which regulates propositional language, can be extended to incorporate the functions of interactional language, namely establishing common ground (grounding) as well as regulating turn-taking (responding). It is further shown that to understand interactional language one has to differentiate between those aspects of interaction that are regulated by grammatical means and those that come about via inferencing, which themselves are based on assumptions about the normal course of a conversation. Finally, it is shown that the study of interactional language requires a mix of methodologies in order to accommodate the role of context.

Chapter 7 concludes the monograph with a summary of the lessons learned from previous scholarship on interactional language and how the Interactional Spine Hypothesis incorporates these lessons and insights. It is shown that a formal approach toward interactional language of this type allows for the development of a typology of interactional language, something that is currently missing in the literature. Potential cognitive underpinnings of the Interactional Spine Hypothesis are discussed and introduced as a new research agenda that has the potential to shed light on the old question regarding the relation between language, thought, and communication. Finally the chapter concludes with an outlook of potential novel research avenues to pursue in light of the Interactional Spine Hypothesis. This includes logophors, genre and style, information structure, the role of intonation, and the relation between speech act and clause-types.

Chapter 5 presents a case-study of confirmationals and introduces a syntactic analysis within the framework of the Interactional Spine Hypothesis. Confirmationals are units of language which express a request for confirmation. I show that the target of confirmation can differ depending on the syntactic context. This is an instance of multi-functionality, which is best analyzed as being syntactically conditioned. As such the pattern of confirmationals within and across languages provides evidence for the interactional spine; it is the system which regulates the function and distribution of confirmationals. I discuss in detail the kind of variation we observe. That is, within and across languages, confirmationals differ as to who hasauthority over the knowledge to be confirmed, to what degree the belief to be confirmed holds, and when this belief came into existence. Moreover, we also observe that in some languages confirmationals come in full paradigms (e.g., Mandarin Chinese) whereas in others the inventory of confirmationals is much more restricted (English). I further show how confirmationals can be combined with intonational tunes to derive the complex meaning that they may have. Finally, I discuss other units of language that share some properties with confirmationals, such as evidentials.