In this science talk, formally titled “Beyond Main Effects: Individual Variation in Vulnerability and Resilience,” Nathan A. Fox, of the University of Maryland, talks about the limitations of traditional early childhood intervention studies, which examine the effects of programs on large groups of children with the hope that one size fits all. But, because children (and adults) differ in terms of reactivity and self-regulation, new interventions must take into account these individual differences and incorporate individual approaches. Nathan Fox is the Distinguished University Professor, Department of Human Development; and Director, Child Development Laboratory, at the University of Maryland. He is also Science Co-Director of the National Scientific Council on the Developing Child.