Ninety two volunteers drank coffee and listened to a white noise machine. They were also told to hit a button when the Bing Crosby song "White Christmas" played in the background. The song never played, but those who had about five cups of coffee or more were most likely to think they heard it.
Researchers say the combination of caffeine and stress affects the likelihood of experiencing a psychosis-like symptom.
Results are in the journal Personality and Individual Differences.