Briana N. Horwitz, Ph.D., is an assistant professor in the Department of Psychology at California State University, Fullerton. She completed her undergraduate studies at The University of California, Los Angeles and her doctoral studies at the University of California, Irvine. She also served as a postdoctoral fellow under the advisement of Dr. Neiderhiser at the Pennsylvania State University. Her research interests are in understanding the sources and directions of the associations among interpersonal relationships and functioning across the lifespan and more specifically to investigate how genetic and environmental factors explain these associations. Jenae M. Neiderhiser, Ph.D., is Liberal Arts Research Professor in the Department of Psychology and Professor of Human Development and Family Studies at The Pennsylvania State University. She completed her undergraduate studies in Psychology at The University of Pittsburgh and her doctoral studies in Human Development and Family Studies at The Pennsylvania State University. She is currently serving as Associate Editor for the Journal of Research on Adolescence and is on the editorial board of Development and Psychopathology and Child Development. She is also serving as a board member for the Society for Prevention Research. Her research interests are in understanding the interplay between genes and environment throughout the lifespan. The environmental influences that she has examined most closely are interpersonal relationships-including parent-child, spouse, sibling, and peer relationships. Examining how individuals influence their environments, in part because of their genetically-influenced characteristics, has long been a focus on her work.