In December 1988, two pairs of twin boys were born in Colombia. One twin from each pair was accidentally given to the wrong mother — a mistake that wasn't discovered for decades. The twins' story is a tragedy, a soap opera, and a science experiment, all rolled into one. It also gives us clues about the role that genes and the environment play in shaping our identities. We talk with psychologist Nancy Segal about her work with twins, and her encounters with these now-famous brothers. For research related to this episode, please visit https://n.pr/2uvpvPe