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 eroded, or even been disproven outright, by a revolution in the study of animal cognition. Take the way octopuses use coconut shells as tools; 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 explores 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, and how we've underestimated their abilities for too long. People often assume a cognitive ladder, from lower to higher forms, with our own intelligence at the top. But what if it is more like a bush, with cognition taking different forms that are often incomparable to ours?