1. Department of Human Behavioural Ecology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
2. Department of Empirical Linguistics, Goethe University, 60323 Frankfurt am Main, Germany
3. Department of Linguistic and Cultural Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
4. Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, MCZ 540B, USA
5. Tai Chimpanzee Project, Centre Swiss des Recherches Scientifiques, 01 BP 1303, Abidjan, Côte d'Ivoire
6. The Ape Social Mind Lab, Institut des Sciences Cognitives, CNRS, 67 Boulevard Pinel, 69675 Bron, Lyon, France