From Philosophy of Science and Psychiatry by Rachel Cooper
In 1973 Rosenhan published his famous paper "Being Sane in Insane Places." Rosenhan had persuaded eight sane people to see whether psychiatrists could distinguish them from the insane. The pseudo-patients told hospital admissions staff that they heard a voice that said “thud”. All eight were promptly admitted. Once admitted, the pseudo-patients acted as normally as they could within the hospital environment. Despite this, the subjects were still perceived by hospital staff as mentally ill. Within the context of the mental hospital, their normal behavior was interpreted as manifesting psychopathological disturbance. For example, a “patient” who kept notes of his experiences was described as indulging in “excessive writing activity”. Each pseudo-patient was detained for between seven and fifty-two days. Even on release they retained a diagnosis: “schizophrenia – in remission”. It seems that the hospital staff considered the subjects to be mentally ill because that is what they expected.