What separates your mind from an animal's? Maybe you think it's your ability to design tools, your sense of self, or your grasp of past and future-all traits that have helped us define ourselves as the planet's preeminent species. But in recent decades, these claims have been eroded, or even disproven, by a revolution in the study of animal cognition: take the octopuses that use coconut shells as tools; the elephants that classify humans by age, gender, and language; or Ayumu, the young male chimpanzee at Kyoto University whose flash memory puts that of humans to shame. Based on research involving crows, dolphins, parrots, sheep, wasps, bats, whales, and of course chimpanzees and bonobos, Frans de Waal demonstrates that we have grossly underestimated both the scope and the depth of animal intelligence. He offers a firsthand account of how science has stood traditional behaviorism on its head by revealing how smart animals really are.