What does the term 'developmental psychology' study?

Developmental psychology is a branch of psychology that focuses on the changes and growth that occur throughout a person's life, from infancy through old age. This field examines how people develop cognitively, emotionally, socially, and physically as they age, exploring aspects such as language acquisition, moral reasoning, and identity formation. Researchers in this field analyze various stages of development, including childhood, adolescence, adulthood, and elder years, to understand the processes that influence human behavior over time.

The other options pertain to important areas of psychology but do not encapsulate the broad scope of developmental psychology. While genetics and brain chemistry are significant to understanding behavior and emotions, and social interactions in childhood are a component of development, they do not represent the full range of changes and influences considered in developmental psychology. Thus, focusing on the overall changes across the lifespan is what differentiates this field from others within psychology.