Joint action

Joint action is coordinated activity in which two or more individuals adjust their contributions in relation to one another to achieve an outcome together. The contributions need not be identical. Carrying a table, for example, requires complementary lifting forces and adjustments to a partner's timing and movements.

An illuminating contrast is between matching an external beat and coordinating with a responsive partner. Two people can follow the same metronome without responding to each other; in a duet, each may also anticipate and adjust to the other's timing. Distinguishing these arrangements helps identify what social coordination contributes beyond a shared stimulus.

One experimental approach distributes a task's responses between partners. In Natalie Sebanz and colleagues' 2003 study, a spatial stimulus-response compatibility effect appeared when a one-response task was performed beside a partner responsible for the other response, but not when it was performed alone. A single person performing both responses supplied another comparison.^[ref]

Such comparisons can test whether another person's possible actions enter an individual's planning. The shared setting and the mechanism producing coordination must be distinguished: merely placing two people in the same room does not identify how they organize their actions.