The Social Simon Effect (SSE) occurs in a Go/Nogo setting (joint condition) when interacting with a partner, but not in an individual condition. This seminal finding has started the discussion regarding the underlying underpinnings, being social (e.g. co-representation of the co-actor’s task) or nonsocial (e.g. reference frame) in nature. Albeit this debate is far from settled, the present study investigates whether the SSE would still be present with the involvement of more then two participants. Here, three participants, i.e. two co-actors and one confederate, performed a Go/NoGo Simon task together. The presence or abscense of the confederate varied between subjects. The seating position of both co-actors varied between subjects in such a way that half of the co-actors were seating directly next to one another and the confederate (or an empty chair) on the side, whereas in the other group, the confederate was placed between both co-actors. The Simon task was performed as a joint Go/NoGo task (with co-actor) and individual Go/NoGo task in a within subjects design. The study followed a 2 Seating Position (middle vs. outer) x 2 confederate (presence vs. absence) x 2 Stimulus compatibility (compatible vs. incompatible) x 2 Setting (joint vs. individual) design. Both co-actors responded to the color of the stimuli, whereas the confederate reacted to the stimulus shape. In the talk, results will highlight the role of the triad and seating position for joint action and therefore also the role of social and nonsocial factors underlying the social Simon effect.