On Inside Animal Minds’ third and final installment, “Who’s the Smartest?”, we ask “What makes an animal smart?”. Many scientists believe the secret lies in relationships. Throughout the animal kingdom, some of the cleverest creatures — including humans — 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.