Final answer:
Rosenhan's 1973 study used participant observation to investigate psychiatric hospitals, demonstrating systemic issues in psychiatric diagnosis and labels.
Step-by-step explanation:
Rosenhan's study in 1973, which is often cited in the realms of psychology and psychiatry, involved a method known as participant observation. This technique entails researchers immersing themselves into the daily lives and activities of a group to gather data from their observations while being part of that context. To elaborate, Rosenhan's experiment involved having healthy individuals, including himself, admitted to psychiatric hospitals by pretending to hear voices. They acted normally afterwards, but all were diagnosed with psychiatric illnesses, suggesting systemic issues in psychiatric diagnosis. This seminal study was significant in showing that psychiatric labels could be misleading and have lasting effects, thereby critically analyzing mental health institutions.