My aunt had headaches for years. She tried everything. Nothing worked for long. Then her doctor gave her new tablets, and within a month the headaches almost stopped. She told the whole family. She told strangers in the pharmacy. She recommended them to her neighbours. Two years later, she read an article and discovered that the tablets were part of a study. Half the patients had received the medicine. The other half had received nothing at all, just sugar in the shape of a pill. She wrote to the hospital and asked which group she had been in. They told her. She had been in the sugar group. My aunt was furious for about a week. She felt tricked. She had defended those tablets in front of the whole family. Then something strange happened. The headaches came back. Her doctor was not surprised. He explained that the effect is real and measurable, that it works through expectation, and that knowing about it usually destroys it. Pain responds strongly, he said, because pain is not only a signal but also an interpretation. "So it was in my head," my aunt said. "Your head is where pain is," he replied. She takes the real medicine now, and it helps, though less than the sugar did. She still tells the story at family dinners. Her version has become shorter over the years, and the ending has changed. She now says, "The pills worked until I understood them," which is roughly correct.