Sellaro, R. 1 , Treccani, B. 1 , Rubichi, S. 2 & Cubelli, R. 1
1 University of Trento
2 University of Modena & Reggio Emilia
The joint Simon effect refers to the finding that, when two participants, sitting close to each other, respond each to one of the two possible values of a lateralized stimulus (i.e., they perform two complementary Go/NoGo tasks), responses are faster when the position of the stimulus corresponds to the position of the response, that is, to the position of the responding participant. The present study aimed at investigating the social (i.e., task sharing) and spatial (i.e., response position coding) factors underlying this effect. Participants performed a Go/NoGo task first individually, then either imaging themselves responding to the NoGo stimuli or co-operating with another person acting in another room. The Simon effect occurred only when participants spatially coded both alternative responses within their own task representation. Conversely, the belief of co-acting with another individual who performed the complementary task (i.e., the co-actor was thought to respond to the actor’s NoGo stimuli), without knowing the co-actor’s position, induced the implementation of a division-of-labor mechanism, which led participants to ignore the alternative response (i.e., the co-actor’s response), thus eliminating the Simon effect.