Cheney, Dorothy L. and Robert M. Seyfarth. How Monkeys see the World. Chicago: University of Chicago Press, 1990.

Dennett, Daniel C. Consciousness Explained. Boston: Little, Brown & Company, 1991.

Durrant, Michael, ed. Aristotle's De Anima In Focus. London and New York: Routledge, 1993.

Nagel, Thomas "What Is It Like to Be a Bat?" The Philosophical Review, vol. LXXIII, no. 4, October 1974. 435-450