You can divide all living creatures into two camps. We humans are in one camp, along with lots of other things like dogs and birds and trees and caterpillars.

Host Ira Glass visits Arlington Racetrack on opening day with four regulars who explain their quasi-scientific systems for winning.

Ira visits marital researcher John Gottman, who's part of a generation of researchers that have revolutionized the way we see marriage by observing successful and unsuccessful marriages and trying to figure out what the successful happy ones are doing that the ones who end up in divorce are not. Marriage research and links to marriage education programs for couples are online at www.smartmarriages.com.