Researchers at La Trobe University (Melbourne, Victoria, Australia) studied 92 people with different amount of intakes of coffee each day, along with different stress levels.
Each subject was given a hearing test that first included hearing American crooner Bing Crosby singing “White Christmas.” [Listen for yourself at YouTube's "White Christmas/Bing Crosby".]
Then, the second part of the hearing test included only static (definitely not as much holiday spirit!).
However, during this part of the test they were asked if they heard Bing Crosby sing one of the most popular Christmas songs of all time “White Christmas.”
They found that people who were highly stressed out and drank a lot of coffee each day were three times more likely to hear imaginary songs, like Bing singing White Christmas than were people not stressed out and who drank no or low amounts of coffee each day.