Groups the psychologists whose primary work concerns how thought, behavior and social bonds change across the life span. Belongs here: Jean Piaget, Lev Vygotsky, John Bowlby, Harry Harlow, Eleanor Gibson, Edward Tronick, Erik Erikson, Lawrence Kohlberg, Mary Ainsworth, Diana Baumrind, Alexei Leontev, Sergei Rubinstein, Charlotte Buhler, Florence Goodenough, Nancy Bayley, Laura Carstensen and Simon Baron-Cohen. A figure whose child-focused research centers on learning mechanism rather than developmental stage or process is filed under educational or cognitive psychology instead.