Action co-representation: the joint SNARC effect.

Traditionally, communication has been defined as the intentional exchange of symbolic information between individuals. In contrast, the mirror system provides a basis for nonsymbolic and nonintentional information exchange between individuals. We believe that understanding the role of the mirror system in joint action has the potential to serve as a bridge between these two domains. The present study investigates one crucial component of joint action: the ability to represent others' potential actions in the same way as one's own in the absence of perceptual evidence. In two experiments a joint spatial numerical association of response codes (SNARC) effect is demonstrated, providing further evidence that individuals form functionally equivalent representations of their own and others' potential actions. It is shown that numerical (symbolic) stimuli that are mapped onto a spatially arranged internal representation (a mental number line) can activate a co-represented action in the same way as spatial stimuli. This generalizes previous results on co-representation.We discuss the role of the mirror system in co-representation as a basis for shared intentionality and communication.