1. Department of Psychology, University of California, Berkeley , Berkeley, CA 94720-1650, USA
2. Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology , Leipzig 04103, Germany
3. Comparative Cognition, Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna, University of Vienna , Vienna 1210, Austria
4. Department of Psychology, Harvard University , Cambridge, MA 02138, USA
5. School of Psychology and Neuroscience, University of St Andrews , St Andrews KY16 9AJ, UK
6. Department of Psychology, University of Portsmouth , Portsmouth PO1 2UP, UK
7. Department of Developmental Psychology, Georg-Elias Müller Institute of Psychology University of Göttingen , Göttingen 37073, Germany