Ideomotor action in cooperative and competitive settings.

Ideomotor movements may arise in observers while they watch other people's actions. Previous studies have shown that ideomotor movements are guided by both perceptual and intentional characteristics of the actions being observed (perceptual induction and intentional induction, respectively; cf. Knuf, Aschersleben, & Prinz, 2001; de Maeght & Prinz, 2004). In the present study we explore the functional basis of intentional induction. More specifically we raise the issue of whose intentions count for intentional induction: observers' own intentions or observees' (implied) intentions? We studied ideomotor movements in a cooperative and a competitive task setting. In the cooperative setting observers' and observees' intentions were identical, but in the competitive setting they were different. Results indicate that ideomotor movements are guided by the observers' own intentions, not the observees' implied intentions. Our findings suggest that, though observers understand the intentions of others, their ideomotor movements are guided by their own intentions, expressing what they themselves wish to see the other is doing.