Rationality in joint action: Maximizing co-efficiency in coordination

Abstract

When people perform simple actions, they often behave efficiently, minimizing the costs of movement for the expected benefit. The present study addressed the question whether this efficiency scales up to dyads working together to achieve a shared goal: do people act efficiently as a group, or do they minimize their own or their partner’s individual costs even if this increases the overall cost for the group? We devised a novel, touchscreen-based, sequential object transfer task to measure how people choose between different paths to coordinate with a partner. Across multiple experiments, we found that participants did not simply minimize their own or their partner’s movement costs but made co-efficient decisions about paths, which ensured that the aggregate costs of movement for the dyad were minimized. These results suggest that people are able and motivated to make co-efficient, collectively rational decisions when acting together.