Language-Invariant Strategies of Navigating Transitions in Joint Activities: Forms and Functions of Coordination Markers.

Goal-directed tasks unfold in hierarchies of larger and smaller sub-tasks, and pursuing them jointly implies that participants must agree on whether they are continuing an ongoing sub-task (horizontal transition) or switching to the next sub-task (vertical transition). Previous research indicates that humans employ short and efficient coordination markers as procedural conventions to distinguish horizontal (e.g., in English, with yeah and uh-huh) and vertical transitions (with okay, all right). However, it remains unclear (1) whether such words serve as potentially universal coordination devices and (2) which properties make some markers more suitable for horizontal versus vertical transition contexts. We hypothesized that horizontal transitions in ongoing sub-tasks are associated with higher dual-tasking interference between verbal coordination and the nonlinguistic task, therefore, constraining the lexicality of coordination markers. In our experimental study, we assessed how speakers of three typologically diverse languages (Swiss French, Vietnamese, and Shipibo-Konibo; N = 232) used coordination markers to navigate a joint LEGO-building task. We found that in each language, coordination markers comprise a system of transition-specific conventions and that participants strategically deployed markers with minimal lexical and acoustic forms (uh-huh, mm) and repetitions in horizontal transitions, while more lexicalized markers (e.g., okay) in vertical transitions. Our findings suggest that (1) coordination markers are potentially universal linguistic devices for navigating joint activities and (2) the forms of coordination markers might be shaped by the constraints of their primary interaction context (here, horizontal and vertical transitions). Our study provides new evidence of how interactional settings might selectively shape language use through the forces of convergent language evolution.