Answer:
Development psychology
Explanation:
Development psychology is the psychology that explains about the consistency, change, and growth in the lifespan. Developmental psychology is the psychology that focuses on how people think, feel and behave in an environment.
This proportion of theories has been focused on the development of a person's childhood and lifespan. The developmental psychologist study about the different areas of the lifespan such as the emotions, psychological, biological and sociological.
Thus here Matias's case is just like the that belongs to the area of developmental psychology.