Abstract
One explanation for the joint Simon effect (J-SE) is the co-representation account, which claims that one represents their own and the co-actor's action in a functionally equivalent way (Sebanz et al., 2003). Using the response-discrimination hypothesis (Ansorge & Wühr, 2004) as an alternative, we examined whether spatially discriminated responses could give rise to the J-SE. In addition to the joint Simon task (JA) we introduced two independent tasks in which the co-actor simply initiated each trial by pressing the opposite (JOK) or same response key (JSK) to their partner. We collected behavioural (RT) and EEG (P3) data to examine how action planning and inhibitory control were affected in a complementary vs. independent task setting in a joint ("social") context. RT results showed a J-SE in the JA and JOK tasks. P3 data suggested that in the JA and JOK tasks, there was less conflict when selecting a response compared to a solo (go/no-go) condition where there was no partner. We propose that in both the JA and JOK tasks, the to-be-ignored stimuli (which specified a spatially distinct, potential response) were treated differently in the joint context. In the JA task, less inhibitory control was required because one can "loaf" while their co-actor responded to the to-be ignored stimuli. In the JOK task, less inhibitory control was required because the co-actor performed an independent task. When performing the task alone, increased inhibition was required to withhold potential responses because there was no one to "pick up the slack."Acknowledgments: This research was funded NSERC.