Developmental psychology is the study of the human mind across the life span. Unlike other areas of psychology--personality, cognitive, social--developmental psychology is explicitly concerned with how the rules of human behavior change over time. All of the methods used in psychology can be, and are, applied to the study of development. These range from neurobiological studies of the brain's growth to studies of the effect of social context on a child's future behavior. Throughout this SparkNote, we emphasize both the experimental findings that have changed our conception of development and the research methods that have made such findings possible.

This SparkNote on developmental psychology is divided into sub-areas that parallel psychology as a whole: language, cognition and perception, and social and emotional psychology. Language is an essential part of human cognition, but it is here given a separate section because it has served as a key case for understanding cognitive development more generally.

The introduction is divided into three subsections: Methods of Developmental Psychology, Theories of Developmental Psychology, and Sources of Developmental Change. In the first section, we focus on the types of studies and experimental methods that are used to address the questions of developmental psychologists. In the second section, we focus on the broad types of developmental theories that have been advanced. In the third section, we discuss some of the issues that we face when we try to determine the cause of changes in behavior over the life course.