Ask people and they immediately know - they're either a dog person or a cat person. What is this all about? This film launches an in-depth investigation into the great divide between dogs and cats and just what draws people to these two polarizing pets. Animal behaviorists, psychologists, trainers and devoted owners all weigh in. Dogs, we find, are geniuses at reading what we want. And the complex cat-human bond can be as fickle or as deep as a marriage. Funny, touching and provocative, NATURE asks how well we really know our best friends and why we love them so much.