In everyday life, people must often determine how much time and effort to allocate to cooperative activities. In the current study, we tested the hypothesis that the perception of others’ effort investment in a cooperative activity may elicit a sense of commitment, leading people to allocate more time and effort to the activity themselves. We developed an effortful task in which participants were required to move an increasingly difficult bar slider on a screen while simultaneously reacting to the appearance of virtual coins and earn points to share between themselves and their partner. This design allowed us to operationalize commitment in terms of participants’ investment of time and effort. Crucially, the cooperative activity could only be performed after a partner had completed a complementary activity which we manipulated to be either easy (Low Effort condition) or difficult (High Effort condition). Our results revealed participants invested more effort, persisted longer and performed better in the High Effort condition, i.e. when they perceived their partner to have invested more effort. These results support the hypothesis that the perception of a partner’s effort boosts one’s own sense of commitment to a cooperative activity, and consequently also one’s willingness to invest time and effort.

In the current study, we separately tested whether coordinated decision-making increases altruism and whether it increases trust. To this end, we implemented a paradigm in which participants repeatedly perform a coordinated decision-making task either with the same partner on every trial, or with a different partner on each trial. When both players coordinate on the same option, both are rewarded. In Experiment 1 (N = 52), participants were sometimes presented with tempting opportunities to defect. In Experiment 2 (N = 97), participants sometimes had to decide whether or not to trust that their partners had resisted such tempting opportunities. The results show that repeatedly coordinating with the same partner increased participants’ resistance to temptation (Experiment 1) but did not increase trust (Experiment 2). These findings support the hypothesis that coordinating with a partner increases altruistic motivation towards that partner; they do not support the hypothesis that coordinating boosts trust.

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Joint action enables us to achieve our goals more efficiently than we otherwise could, and in many cases to achieve goals that we could not otherwise achieve at all. It also presents us with the challenge of determining when and to what extent we should rely on others to make their contributions. Interpersonal commitments can help with this challenge – namely by reducing uncertainty about our own and our partner’s future actions, particularly when tempting alternative options are available to one or more parties. How we know whether a commitment is in place need not, however, be based on an explicit, identifiable event; in many cases, joint action is stabilized by individuals’ experience of an implicit sense of commitment, which is sensitive to subtle situational cues such as the effort costs invested by one or more agents. While an emerging body of work has investigated the conditions under which a sense of commitment may emerge and/or be strengthened, little attention has been paid to the conditions under which people are comfortable dissolving commitments. Specifically, what are the factors that modulate people’s motivation and which determine whether circumstances merit the dissolution of a commitment? After evaluating and rejecting the answers to this question suggested by standard approaches to commitment, we develop a new approach. The core insight which we articulate and defend is that, when considering whether new information or changing circumstances merit the dissolution of a commitment, people virtually bargain with their partners, performing a simulation of a bargaining process with the other person, including imagining how the other will feel and act towards them, and what effect this will have on them. The output of this simulation is a consciously accessible, affective state which provides motivation either to dissolve the commitment or to persist in it. Overall, our account expands our understanding of the phenomenology of being motivated to act committed in joint activity, an area in which existing accounts of interpersonal commitment fall short.