Mainly focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on intellectual, cognitive, neural, social, or moral development. Researchers who study children use a number of unique research methods to make observations in natural settings or to engage them in experimental tasks. Such tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful, and researchers have even devised clever methods to study the mental processes of small infants. In addition to studying children, developmental psychologists also study aging and processes throughout the life span, especially at other times of rapid change (such as adolescence and old age). Urie Bronfenbrenner's theory of development in context (The Ecology of Human Development - ISBN 0-674-22456-6) is influential in this field, as are those mentioned in "Educational psychology" immediately below, as well as many others. Developmental psychologists draw on the full range of theorists in scientific psychology to inform their research.