Testosterone Administration Decreases Generosity in the Ultimatum Game Zak, Paul J. ; Kurzban, Robert ; Ahmadi, Sheila ; Swerdloff, Ronald S. ; Park, Jang ; Efremidze, Levan ; Redwine, Karen ; Morgan, Karla ; Matzner, William Abstract Publication: PLoS ONE Pub Date: December 2009 DOI: 10.1371/journal.pone.0008330 Bibcode: 2009PLoSO...4.8330Z