30.09.2025 Natalia Morozova

Human cognition equips us with the ability to segment ongoing goal-directed events into smaller meaningful steps, a capacity that becomes essential when coordinating tasks with others. Language helps participants coordinate transitions through their tasks by signalling whether to sustain an ongoing step (i.e. make a horizontal transition) or shift to the next one (i.e. make a vertical transition). My work explores the linguistic tools, or coordination markers, that help participants to implicitly distinguish between horizontal and vertical transition contexts, thus facilitating fast and efficient coordination of joint tasks. By using a combination of cross-linguistic, developmental, and experimental approaches, I show that the lexicality, acoustic variability, and the developmental trajectories of coordination markers might be universally constrained by the interactional ecologies of their respective transitions. There findings provide new insights into how language evolved to solve coordination problems in social interactions and how the constraints and affordances of these interactions might lead to linguistic convergence, even across geographically and typologically distant languages.