Token transfers among great apes (Gorilla gorilla, Pongo pygmaeus, Pan paniscus, and Pan troglodytes): species differences, gestural requests, and reciprocal exchange

Journal of Comparative Psychology (2009) - Comment
pubmed: 19929106 doi: 10.1037/a0017253 issn: 1939-2087 issn: 0735-7036

Marie Pelé, Valérie Dufour, Bernard Thierry, Josep Call