In this book, field and laboratory researchers show that the Great Apes are capable of thinking at symbolic levels, traditionally considered uniquely human.

Henrich et al. convincingly caution against the overgeneralization of findings from particular human populations, but fail to apply their own compelling reasoning to our nearest living relatives, the great apes. Here we argue that rearing history is every bit as important for understanding cognition in other species as it is in humans.

In recent years, explanations of primate cognition highlighted clever arguments, rather than different ability. In the target article, definitions unify, explanations rely on basic nervous system functioning, theory is built on data that fit, and the emphasis is on evolutionary continuities. This commentary describes complexities inherent in the development of empathy that are not accounted for in Preston & de Waal's theory.

Heyes argues that nonhuman primates are unable to imitate, recognize themselves in mirrors, and take another's perspective, and that none of these capabilities are evidence for theory of mind. First, her evaluation of the evidence, especially for imitation and mirror self-recognition, is inaccurate. Second, she neglects to address the important developmental evidence that these capabilities are necessary precursors in the development of theory of mind.

An evolutionary model of crying requires consideration of nonhuman primate data. Chimpanzees do not have colic. Although they have a peak of fussiness at 6 weeks with a decline by 12 weeks whether raised by biological mothers or in a human nursery, their crying is always consolable. Colic may be a by-product of delayed rates of brain development; that is, neoteny.