Final answer:
Erik Erikson is the psychologist known for proposing that individuals go through psychosocial changes throughout their lifespan with his theory of personality development featuring eight stages.
Step-by-step explanation:
The psychologist who believed that as people age, they also go through psychosocial changes is Erik Erikson. Erikson created a theory of personality development which posits that personality continuous to change over time and was never truly finished. This theory includes eight stages of development, with each stage representing a conflict or developmental task that occurs throughout an individual's lifespan. While other theorists like Sigmund Freud focused on psychosexual stages, and Abraham Maslow on hierarchy of needs, Erikson emphasized the social nature of our development and the important social relationships at each stage.