"When your dog growls and barks, you might assume that he's angry. But how do you know? You can't very well ask him. Even if you could, it's not at all clear that animals even have emotions like humans do. We still know very little about what emotions are and how they drive behavior. In fact, scientists haven't even been able to reach a consensus on how to study them. In The Nature of the Beast, neuroscientist David Anderson argues that the only way...