Figure 1.

Tentative forward model for action coordination. In coordinative actions, the forward model of each of the interaction partners is assumed to be 3-fold. The elements of the forward model concerning one’s self are depicted in yellow here, green color indicates the representation of the other person (which could also be more persons in an interacting group) and the suprapersonal representation of the joint action is marked in blue. Actual, observable action effects are shown in orange. On layer 1 (Individual Forward Model), one’s own action intention, as derived from the joint goal, is represented. The sensorimotor system thereupon builds a motor command and an according efference copy. The action effect caused by the execution of the motor command is compared with the efference copy in the sensory system. The result of this comparison (sensory congruency or discrepancy) influences the following actions such that the joint goal is approached and reached in the end. On a second layer (Representation of Other’s Forward Model), the other’s action intention and the corresponding implementation with its assumed sensory consequences are represented. With regard to the interaction partner, one’s own sensory system thus compares the expected and the actual action effects. Especially when the involved individuals are highly skilled in their interactive tasks, an additional third layer (Representation of Joint Forward Model) is assumed, in which the joint intention is represented and the joint action and its effects are predicted detached from the individual contribution. Again, a comparison of prediction and outcome takes place in the individual sensory system, thereby determining the progress of coordinated action. The various representational layers of the actors are intertwined by sensorimotor feedback loops.