In contrast to monologues or institutionally regulated interaction, it is the local management and negotiation of turn exchange that is crucial for the organization of conversation. In conversation the issue of who takes a turn at what point in time is not predetermined, but is negotiated between the participants at the moment when it becomes relevant in the interaction. In general, there is a normative orientation to a next speaker taking the turn “on time”, i.e., not too early and not too late, with minimal overlap and minimal gap, after the prior speaker has ended his or her turn. Taking over the floor too early or too late can give rise to inferences concerning possible reasons for noticeably deviating from normative expectations. But how is it possible for turn taking to work so smoothly?
The basic mechanism of turn taking was reconstructed in the seminal paper by Sacks et al. (1974). According to their model, turn taking is organized in two components:
i. a turn-constructional component, dealing with the construction of basic units called “turn-constructional units” (TCUs); and
ii. a turn-allocation component, dealing with the distribution of turns at the end of each TCU for the next such unit.
The system is described as abstract, i.e., context-free, and at the same time adaptable to all kinds of contingencies, thus context-sensitive, locally managed, and party-administered (for an overview see also Levinson 1983 and Sidnell 2010).
In order to explain how smooth turn taking is possible, Sacks et al. assume that TCUs are projectable, i.e., their first possible completion point can be predicted by the recipient in advance of its occurrence. Such a possible completion point is referred to as a “transition-relevance place” (TRP) (Sacks et al. 1974:703). It is here that the rules of the turn-allocation component become relevant and result either in the transfer of speakership or in a continuation by the same speaker. According to this model, then, the continuation of the same speaker after a first TRP is an interactional achievement resulting from the fact that other participants have refrained from taking the turn themselves.