Neural activities triggered by viewing other's in pain have been previously reported to be modulated by various factors. How instructions of cooperation and competition can influence these activities has not been explored yet. In the current study, participants were instructed to play a game cooperatively or competitively with a partner. During the game, pictures showing an anonymous individual's hand or foot in painful or non-painful situations were randomly presented in an oddball style. The event-related potentials (ERPs) when the participants passively observed these pictures under different instructions were compared. We found a significant interaction of Instruction × Picture on the P3 component, where only under competitive instruction did the painful pictures elicit significantly larger amplitudes than the non-painful pictures, but not under the cooperative instruction. This result indicates that the participants were more responsive to other's pain in a competitive context than in a cooperative context.
Keywords: Competition; Cooperation; ERPs; Other’s pain; P3.