The question of animal sentience, self-awareness and intelligence would have been heresy in the scientific community 50 years ago when animals were considered mere automatons–their behavior genetically hard-wired. But the possibility that they make choices, have emotions and create unique cultural identities has received a lot more attention in the past 15 years. While it is still controversial, there is growing evidence that many animals are much smarter and more sophisticated than we knew—and that brings up some difficult issues.