1. Cheney, D. & Seyfarth, R. Baboon Metaphysics (Univ. Chicago Press, 2008).
2. Gallistel, C. R. The Organization of Learning (MIT Press, 1990).
3. Hauser, M. D. Wild Minds (Henry Holt, 2000).
4. Shettleworth, S. Cognition, Evolution and Behavior (Oxford Univ. Press, 1998).
5. Tomasello, M. & Call, J. Primate Cognition (Oxford Univ. Press, 1997).