In pseudo-patient study (PPS), fieldworkers cloak their identities and intentions and pose as “patients.” This enables them to observe the practice of healthcare from within a naturalistic, nonreactive research setting. Rosenhan and his assistants conducted the most famous PPS, where they faked symptoms of schizophrenia so that they could gain admittance to a mental-health facility and observe the treatment that genuine patients were receiving. More subtle pseudo-patients might arrange “appointments” over the phone, after reporting varying levels of health insurance. Others might provide dummy lab specimens or test a physician's response to technical questions. A few genuine patients have transformed their legitimate stays in the hospital into fieldwork, transforming themselves into disguised participant-observers.