“…Overall, 37 studies (58%) designed symmetrical social biofeedback systems, 23 studies (36%) designed asymmetrical ones and four studies engineered opportunities for both. In symmetrical systems, it was most common for users to receive biofeedback about their own physiological state together with that of other users' (n=14; [2,52,54,67,70,72,73,75,77,85,95,116,119,121]). In 12 studies, users only received feedback about states of co-users and not their own [3,29,30,45,55,65,87,91,94,110,125,133], while in four studies only aggregated measures of physiology were shown to both players [83,100,107,142].…”