In 1973, psychologist David Rosenhan wanted to see if psychiatrists could really tell who was mentally ill. So, he and seven others faked symptoms to get into hospitals—just claiming they heard words like “empty” and “thud.” Once admitted, they acted completely normal, but doctors still labeled them schizophrenic and ignored their sanity. They were stuck for weeks, proving that psychiatric diagnoses were more about labels than reality. His study shook up mental health care and changed how people viewed psychiatric hospitals.