Answer:
Case study
Step-by-step explanation:
A Case study refers to the use of a descriptive research approach to obtain an in-depth analysis of a person, group, or phenomenon. Through a case study, psychologists investigate an specific person or group within their real-life context.
In a case study, researchers gather a great deal of information from one individual, they observe their day-to-day life and describe it in order to have a better understanding of said person and the changes he/she has gone through over his/her lifespan.