Psychiatrists at the Medical College of Georgia ran a camera while a 25-year-old housewife sat under hypnosis and, on cue, stopped being one person and became another. The footage of that switch is the quiet center of one of the strangest case studies in American psychiatry, and it helped write multiple personality disorder into the diagnostic manual that doctors still consult today.

Here is what actually happened. In 1952, a woman who would be called "Eve White" came to Corbett H. Thigpen and Hervey M. Cleckley complaining of blinding headaches and blackouts. During treatment a second personality surfaced, a flirtatious, reckless figure they named "Eve Black," followed later by a calmer third self, "Jane." Thigpen and Cleckley documented the case in a 1954 paper for the Journal of Abnormal and Social Psychology, "A Case of Multiple Personality," then expanded it into the 1957 bestseller The Three Faces of Eve. The film adaptation won Joanne Woodward the Academy Award for Best Actress that same year. The patient's real name was Chris Costner Sizemore, and she did not go public until 1975.

The hard evidence is unusually rich for a case like this. The two clinicians logged more than a hundred hours of evaluation across roughly fourteen months. They ran EEG recordings, hoping to find that the alternating personalities produced measurably different brain traces. They administered IQ tests, memory tests, and Rorschach inkblots to each personality separately, and they filmed the transitions. This was not a single dramatic anecdote; it was an attempt, however crude by modern standards, to pin a slippery phenomenon to instruments and paper.

And the instruments did register something. The psychometric profiles of the personalities differed; the projective test results diverged in ways that impressed contemporaries. That documentary apparatus, the films and the test batteries, is exactly why the case carried so much weight in the long argument over whether multiple personality is a real condition. When the diagnosis was formalized as Multiple Personality Disorder in the 1980 third edition of psychiatry's Diagnostic and Statistical Manual, the cultural runway had been built largely by Eve.

Now the skeptical reading, which the case demands. EEG differences between emotional states are not proof of separate selves; a relaxed person and an agitated person produce different traces too. Hypnosis is a notoriously suggestible state, and a clinician who names and addresses a personality can help summon and stabilize it. Critics of the broader diagnosis have long argued that highly suggestible patients, guided by clinicians who expect to find alters, can generate them, and that the explosion of multiple-personality cases after the 1970s looked suspiciously like a fashion rather than an epidemic. The filmed switch proves a switch occurred. It does not prove what the switch was.

The most damning complication comes from Sizemore herself. She publicly rejected the tidy three-faces narrative, saying the real total was around twenty-two personalities and that the clinicians' account had flattened and distorted her experience. She even had to fight a legal battle in the 1980s over the rights to her own life story. If the famous patient says the famous version is wrong, the case stops being a clean piece of evidence and becomes something more uncomfortable: a record of how a publication, a film, and an Oscar can outrun the messy clinical reality they claim to depict.

What endures is the recursion. A filmed session helped legitimize a diagnosis; the diagnosis legitimized the search for more cases; the cases fed an industry; and the woman at the origin spent decades correcting the story written in her name. The footage is real. The switch is on tape. The open question, never cleanly answered, is whether the camera captured a disorder that was already there, or helped author one that the rest of us then went looking for.