Liebal, K., & Kaminski, J. (2012). Gibbons (Hylobates pileatus, H. moloch, H. lar, Symphalangus syndactylus) follow human gaze, but do not take the visual perspective of others. Animal Cognition, 15(6), 1211-1216. doi:10.1007/s10071-012-0543-5.