Observing other's actions affects Social Simon effect

Sebanz et al. (2003, "Representing others' action: Just like one's own?" Cognition, 88, B11-B21) demonstrated that a response selection conflict between two action alternatives (a right and a left button press) that is known to occur within individuals is also observed across individuals in a social setting. A pair of participants in their study responded to pictures of a colored ring presented on an index finger pointing left or right. Each of the pair assigned each color that they had to respond. Their results showed that participants respond more slowly when the finger pointed at their partners than when it pointed at the participants. This phenomenon refers to "social Simon effect". The present study investigated whether the social Simon effect is observed using a colored arrow, instead of a finger pointing. Our results did not show a social Simon effect. However, we provided the evidence that when the partner is in charge of the response in the previous trial, the social Simon effect appeared , whereas it was not observed when the participant is in charge of the response in the previous trial. These results suggested the possibility that although non-social pointing stimulus like an arrow does not lead to the robust activation of partner's task representation, it may be activated depending the previous trials.