Developmental psychology is concerned with both stability and change across the lifespan.
Previously, infancy and childhood were conceptualised as periods of dynamic progress in terms of biological maturation and social and cognitive development, whereas adulthood was largely regarded as a plateau period culminating in inevitable decline in old age. Therefore, much effort was expended in describing infancy and childhood and, to a lesser extent, adolescence, but little attention was directed towards charting adulthood and old age. More recently, the focus has widened to include consideration of conception, prenatal development, changes in adulthood, old age, and death and dying, giving a lifespan perspective. For example, adolescence is not a separate phase in non-technological societies. The chronology of developmental psychology will be outlined to illustrate this point.