For this week's Please Explain, we explore how science is giving us a better understanding of how addiction works, and what that means for how we think about and treat it. We're joined by Fran Smith, author of "The Science of Addiction," National Geographic Magazine's September cover story. We're also joined by expert Dr. Rita Goldstein, a professor of psychiatry and neuroscience at the Icahn School of Medicine at Mount Sinai, who is featured in the article.  Note: Ilya Marritz guest-hosted this segment of "The Leonard Lopate Show."