The effects of simultaneous but unequal response-independent pay to pairs of human subjects on masseter EMG and bodily movements

Electromyographic activity and bodily movement of the masseter muscle were recorded in three pairs of human subjects, where one member of each pair was systematically presented with greater pay and each could reduce the value of money received by the other. The number of biting responses was as high or higher for the subject receiving less money immediately after coin delivery. However, the number of masseter contractions for the subject receiving more money remained higher at other times during the unequal pay conditions. No responses of pay reduction were emitted by any subject toward another.