[1] Univ Michigan, Dept Psychol, Ann Arbor, MI USA
[2] Univ Michigan, Dept Ecol & Evolutionary Biol, Ann Arbor, MI 48109 USA
[3] German Primate Ctr, Cognit Ethol Lab, Gottingen, Germany
[4] Univ Gottingen, Dept Primate Cognit, Gottingen, Germany
[5] Arizona State Univ, Sch Human Evolut & Social Change, Tempe, AZ 85281 USA