Watch Nova season 0 episode 18 online. What makes an animal smart? What forces of evolution drive brains to become more complex? Many scientists believe the secret lies in our relationships. Throughout the animal kingdom, some of the cleverest creaturesâ€”including humansâ€”seem to be those who live in complex social groups, like dolphins, elephants, and apes. Could the skills required to keep track of friend and foe make animals smarter? To find out, NOVA goes inside the social lives of some of the smartest animals on the planet. Off the coast of Florida, we see dolphins team up to catch fish by whipping up a wall of muddy water that drives the meal right into their companionsâ€™ waiting mouths. It seems that the dolphins are working together to plan their hunt. But are they really? Biologists go on a quest to decipher the secrets of animal societies, from the seas of the Caribbean to the plains of Africa. Do dolphins and elephants have “language?” Do chimps have a sense of fairness? And are any animals besides ourselves capable of feeling empathy?