C. Watson and C. Caldwell, “Neighbor Effects in Marmosets: Social Contagion of Agonism and Affiliation in Captive Callithrix jacchus,” Am J Primat 72 (2010): 549; K. Baker and F. Aureli, “The Neighbor Effect: Other Groups Influence Intragroup Agonistic Behavior in Captive Chimpanzees,” Am J Primat 40 (1996): 283.