Understanding cooperation as a distinctly human combination of innate and learned behavior. Drop something in front of a two-year-old, and she's likely to pick it up for you. This is not a learned behavior, psychologist Michael Tomasello argues. Through observations of young children in experiments he himself has designed, Tomasello shows that children are naturally-and uniquely-cooperative. Put through similar experiments, for example, apes demonstrate the ability to work together and share, but choose not to. As children grow, their almost reflexive desire to help-without expectation of reward-becomes shaped by culture. They become more aware of being a member of a group. Groups convey mutual expectations, and thus may either encourage or discourage altruism and collaboration. Either way, cooperation emerges as a distinctly human combination of innate and learned behavior. In Why We Cooperate, Tomasello's studies of young children and great apes help identify the underlying