Joint Action

Defining Joint Action

Joint action refers to cases in which two or more agents coordinate their behavior in pursuit of a goal in a way that is, at least to some degree, intentional and mutual. Typical examples include two people carrying a table, performing a duet, playing a team sport, or coordinating in conversation.

Philosophers distinguish mere parallel action—people doing similar things at the same time—from genuine joint action, which involves some form of shared organization of intentions, expectations, and behavior. Two runners competing in a race act in parallel but not jointly; two people dancing a waltz typically do engage in joint action.

Central debates focus on what must be added to individual agency to yield joint agency: is it enough that each agent intends to do their part knowing the other will do theirs, or must there be a further, irreducible kind of shared intention or collective commitment?

Shared Intention and Collective Agency

A central concept in theorizing about joint action is shared intention—an intention that, in some sense, belongs to multiple agents together.

One influential approach, often called a planning-based or individualist account, is associated with Michael Bratman. On this view, there is no mysterious collective mind. Instead, a shared intention consists in a web of interlocking individual intentions and beliefs. Roughly, for agents A and B to share an intention to do X together:

• A intends that we do X, and B intends that we do X.
• Each intends to do their part in X.
• Each intends that their own part mesh with the other’s part.
• These intentions are common knowledge and guide the agents’ practical reasoning.

Joint action is then grounded in the rational integration of these attitudes across individuals.

In contrast, collective or plural subject accounts, developed by Margaret Gilbert and others, argue that shared intentions involve a distinctively joint commitment that cannot be reduced to a set of private intentions. On this view, when we form a shared intention, we become a plural subject of that intention: we are jointly committed to act as a body. This joint commitment generates obligations; one party cannot unilaterally withdraw without, in some sense, wronging the other.

Some theorists argue for collective agency at a higher level: groups, teams, or institutions can be genuine agents with their own intentions and actions, partly grounded in but not reducible to the mental states of individuals. In this broader context, joint action is a basic building block of more complex group agency, with implications for political philosophy and ethics (e.g., corporate responsibility).

Disagreement between individualist and collectivist accounts centers on whether all the phenomena of joint action—including its normativity and felt “we-ness”—can be captured purely in terms of suitably related individual mental states, or whether an ontologically robust notion of a “we-subject” is needed.

Coordination, Communication, and Embodiment

Joint action also raises empirical and conceptual questions about coordination mechanisms. How do agents keep their actions aligned over time?

Cognitive scientists and philosophers highlight several elements:

• Predictive models and shared plans: Agents rely on representations of what the others will do, often structured as shared or negotiated plans.
• Online feedback and adjustment: Continuous perception of one another’s movements allows for fine-tuned mutual adaptation, as in playing music together.
• Communication: Verbal agreements, gestures, and subtle cues (like eye gaze) establish and sustain joint projects.

An important development is the focus on embodiment. Some accounts stress that coordination is not only a matter of internal intentions but also of sensorimotor coupling. In joint action, bodily movements become interdependent: partners may synchronize rhythms, mirror gestures, or rely on haptic feedback (e.g., the felt weight when carrying a table together).

Minimal joint action theories aim to explain the simplest cases (like two strangers spontaneously synchronizing footsteps) using basic perceptual and motor processes, without positing rich shared intentions. These approaches often draw on dynamical systems models and emphasize that stable patterns of coordination can emerge from reciprocal perception-action loops.

Phenomenological approaches, influenced by thinkers like Husserl and Merleau-Ponty, emphasize the experience of acting together—a sense of “we are doing this” that is not just the sum of “I” experiences. They argue that this “plural first-person perspective” is grounded in embodied interaction and may be prior to explicit planning or verbal agreement.

Normativity and Responsibility in Joint Action

Joint action raises distinctively normative questions about obligation, trust, and responsibility.

On plural-subject accounts, entering into a joint commitment to act together generates obligations of participation and support. Each participant owes it to the others to carry out their role, barring special excusing conditions. This helps explain why simply walking away from a cooperative activity (e.g., abandoning a partner while moving furniture) often feels like more than a merely prudential failure; it appears as a kind of interpersonal wrong.

Even on individualist accounts, norms arise from mutual reliance and the structure of shared plans. When we coordinate our actions, we build expectations into our practical reasoning. Failing to do one’s part may then count as a form of practical inconsistency or as violating reasonable reliance, grounding blame or criticism.

There are also questions of collective responsibility: when a joint action produces harm or benefit—say, a team’s negligent failure leading to an accident—who is responsible? Positions vary:

• Some hold that responsibility fully distributes to individuals, according to their roles and knowledge.
• Others argue that in some cases a group or joint agent can bear responsibility that is not reducible to the sum of individual responsibilities.
• Intermediate views suggest both individual and group-level responsibility can coexist, depending on how decisions and intentions were structured.

Finally, joint action is central to debates on social norms, institutions, and cooperation. Repeated joint actions, stabilized by common expectations and shared understandings, can give rise to enduring practices and norms. Philosophers of social ontology therefore treat joint action as a foundational phenomenon for explaining how complex social realities are built from the coordinated activities of many agents.