In December 1988, two sets of identical twins became test subjects in a study for which they had never volunteered. It was an experiment that could never be performed in a lab, and had never before been documented. This week, we revisit this fascinating story, told by psychologist Nancy Segal, about the eternal tug between nature and nurture in shaping who we are.

If you like our work, please consider supporting it! See how you can help at support.hiddenbrain.org. And to learn more about human behavior and ideas that can improve your life, subscribe to our newsletter at news.hiddenbrain.org.