I understand. Some of my teachers do the same thing.
It is saying that previously you have learned that "developmental psychology" is how people change in their lifetime. There are researches going on still today to understand more specifically on how people change and what might happen while their change either from nature or from someone nurturing you or taking care of you. This means changes that happen when your pregnant, an infant, in childhood, in adolescence, and other stages in adulthood. You have to do a research on how people change during stages in your life. Stages meaning when your pregnant, an infant, in childhood, in adolescence, and other stages in adulthood.
I hope this helps you.