Illustrations of (a) responding to joint attention; (b) initiating joint attention — IJA – PS, “pointing”; (c1, c2, c3) IJA – EC, “alternating gaze”; (d) initiating behavior requests — IBR – PG, “pointing”; and (e) responding to behavior request from the Early Social Communication Scales (Mundy,Delgado et al., 2003; Seibert et al., 1982).