“…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]. Six studies combined the sharing physiology of all users with additional aggregated measures like average metrics [17] and synchrony level between users [46,60,61,82,113].…”