Arthur Aron, PhD, is a Research Professor in the Department of Psychology at the State University of New York at Stony Brook. His research centres on the self-expansion model of motivation and cognition in personal relationships and intergroup relations, including its neural underpinnings and real-world applications. He has published more than 200 scientific papers, including a foundational paper (in collaboration with Dr. Elaine Aron) on his basic theoretical model that has more than 3,000 citations. Another, his earliest on the "shaky bridge study," has become a classic in the field and is cited in nearly every introductory psychology, social psychology and psychology methods text published in the last 20 years. He is also widely known publicly for his groundbreaking brain-scan studies of romantic love and, most recently, for his "36 Questions" for creating closeness. Dr. Aron currently serves on the editorial boards of the Personal Relationships- and Journal of Social and Personal Relationships. He is a Fellow of the American Psychological Association, the Association for Psychological Science, the Society of Personality and Social Psychology, the Society of Experimental Social Psychology and the Society for the Psychological Study of Social Issues. He has received major grants from the National Science Foundation, the Templeton Foundation, the Fetzer Foundation and the Social Science and Humanities Research Council of Canada. He also received the prestigious Distinguished Research Career Award from the International Association for Relationship Research. Elliot J. Coups, PhD, who passed in 2020, received his PhD in social/health psychology from Rutgers University and completed a postdoctoral fellowship in cancer prevention and control at Memorial Sloan-Kettering Cancer Center. When he made his most recent contributions to this text, he was a faculty member in the Cancer Prevention and Control Program at Rutgers Cancer Institute of New Jersey, and associate professor of medicine at Rutgers Robert Wood Johnson Medical School and of health education and behavioural science at Rutgers School of Public Health. Dr. Coups' primary area of research focused on understanding and promoting health-related behaviours among cancer survivors and individuals at risk for cancer. He had a particular interest in skin cancer prevention and control, and had published on a number of relevant topics, including skin cancer-related behaviours among melanoma survivors and their family members, sun protection behaviours among Hispanic individuals, physician screening for skin cancer and indoor tanning. Dr. Coups' research was supported by numerous federal and foundation grants, and he published more than 100 journal articles, book chapters and books. Elaine N. Aron, PhD, is a researcher and writer. Her most widely cited research focuses on the innate temperament/personality trait of sensory processing sensitivity, with research ranging from in-depth qualitative interviews to laboratory experiments, representative surveys and neuroimaging studies. She is also well known for her research in collaboration with Dr. Arthur Aron on close relationships, including 2 seminal books. She has published more than 50 research papers and has given hundreds of invited talks, colloquia and continuing education workshops for professionals. In addition to her academic writing, she has published 8 books for the public based on her research, including the best-selling The Highly Sensitive Person and The Highly Sensitive Child, both translated into over 35 languages.