Coactors who prioritize efficiency in individual contexts minimize the costs of different types of actions in joint action planning.

Abstract

In repeated joint actions composed of identical action types, people consider the expected group effort and choose action options that minimize it (i.e., act coefficiently). We investigated people's joint action planning when coefficiency required the integration of different types of action costs. In a within-subjects experiment in 2019, adults played a touchscreen-based game where they collected objects by choosing one of two actions, tapping, or dragging. The number of required taps and lengths of paths for dragging were systematically manipulated. We measured participants' tapping and dragging durations, estimated individual relative action costs, and evaluated their efficiency in a two-alternative forced-choice condition. We then analyzed decision-making when the same task was embedded in a joint context. When playing alone, 65% of the participants minimized action costs. Decisions in the joint task were best explained by a model incorporating the decision-maker's and the coactor's relative costs: The higher the combined costs of a dyad's tap-and-drag sequence, the less likely this sequence was the chosen course of action. Conditional on individually efficient decision-making, people integrate the relative costs of different actions available to themselves and their partner in joint action planning. This work adds to our understanding of cost-benefit analyses in social interactions. (PsycInfo Database Record (c) 2026 APA, all rights reserved).