The Function and Determinants of Reconciliation in Pan troglodytes Orlaith N. Fraser & Daniel Stahl & Filippo Aureli Received: 19 June 2008 / Accepted: 5 July 2009 / Published online: 23 September 2009 # Springer Science + Business Media, LLC 2009 Abstract Reconciliation (the postconflict affiliative reunion between former opponents) may mitigate costs of aggressive conflict by repairing the opponents’ relationship and reducing stress. We showed that postconflict levels of self-directed behavior were lower after reconciliation than when reconciliation did not occur in chimpanzees (Pan troglodytes) at Chester Zoo, providing support for a stress- alleviating function for reconciliation. Further, we investigated the effects of multiple factors on the occurrence of reconciliation using generalized linear mixed models. We performed 2 separate analyses, a “traditional” analysis and a “targeted” analysis. The former included variables previously used to assess the occurrence of reconciliation in primates, i.e., conflict characteristics, sex combination, and a simple measure of relationship value. The latter included species-specific variables such as the occurrence of consolation (postconflict affiliation from a bystander to the recipient of aggression); initiation of the conflict with a bluff display; and measures of relationship value, compatibility, and security specific to the study group. Whereas the traditional analysis showed that female-female dyads and valuable partners were most likely to reconcile, the targeted analysis showed that Int J Primatol (2010) 31:39–57 DOI 10.1007/s10764-009-9377-7 O. N. Fraser (*) : F. Aureli Research Centre in Evolutionary Anthropology and Palaeoecology, School of Natural Sciences & Psychology, Liverpool John Moores University, Liverpool L3 3AF, UK e-mail: orlaith.fraser@univie.ac.at D. Stahl Department of Biostatistics and Computing, King’ s College, Institute of Psychiatry, SE5 8AF London, UK Present Address: O. N. Fraser Department of Neurobiology and Cognition, Faculty of Life Sciences, 1090 Vienna, Austria