There is a power law of joint communicative effort and it reflects communicative work

A drive towards efficiency seems to regulate communicative processes and ultimately language change. In line with efficiency principles, signed, spoken, and/or gestural utterances tend to reduce in overall effort over repeated referrals in referential tasks. Although theories generally assume multimodality and interaction, this process has mostly been operationalized as individual effort in a single communicative modality. Here we seek to understand reduction of communicative effort in its natural environment, i.e. during multimodal and collaborative face-to-face dialogues about displaced referents. We ascertain that the reduction in joint effort (y) over repeated referrals (x) follows a negative power relationship, y = a*x^c, where a and c are constants. This reduction in communicative effort is multimodal, occurring across gesture, speech, prosody, and turn taking, and it is interactive, based on joint effort. The pattern is robust, being confirmed through reanalyses of published datasets about (individual) effort reduction. Crucially, the pattern is communicatively relevant. The coefficient of the power relationship predicts change and convergence in interlocutors' conceptualizations of the communicative referents over the interaction. The negative power relationship reflects therefore how effort translates into mutual understanding - a process we call communicative work. We suggest that the power function captures an exploration-exploitation trade-off during human dialogue which emerges from multiscale processes. Joint conceptualization of novel referents benefits from early conceptual exploration followed by later exploitation of selected signals. The current report proposes a novel 'power law of joint communicative work' that is relevant for linguistic theory, agent-based modeling, and experimental psychology.