Tap the rhythm of “Twinkle, Twinkle Little Star” on a desk and it sounds obvious. You can hear the song. Surely anyone could.
In 1990 a Stanford graduate student in psychology, Elizabeth Newton, turned that feeling into an experiment for her dissertation. She recruited 80 undergraduates in pairs and split each pair into a tapper and a listener. The tapper got a list of 25 well-known songs, among them “Yankee Doodle,”“Silent Night” and “Twinkle, Twinkle Little Star,” and chose three. The two sat with their backs to each other. The tapper tapped. The listener wrote down a guess.
After each song, the tapper estimated the chance that the listener had got it right. The estimates averaged 50%, ranging from 10% to 95%. Asked how many people in an audience of 100 would name the tune if they heard the tapping amplified in a recital hall, the tappers said 51% on average.
Newton then counted the listeners’ answers. Across 120 songs there were three correct guesses: 2.5%, a rate outside the whole range of the tappers’ estimates.
She had expected the gap, and named its source. While a tapper taps, the tune plays in her head, with all its melody and phrasing. A note she imagines held is, to the listener, only a pause. “A tap, outside of the vivid musical context into which you have incorporated it,” Newton wrote, “is just a tap.”
The next step showed how hard the feeling is to shake. The experimenter tapped each pair’s first song and asked both partners what share of an audience would name it. The tappers, now hearing their own song from outside, still said 50%. The listeners said 3%. In a second part of the study, 80 students who had never tapped or listened were told the tune in advance and heard it tapped. Their guesses also averaged 50%.
Years later Chip and Dan Heath retold the study in their book Made to Stick. “The tapper is hearing everything,” Chip Heath told NPR, “and what the listener is hearing is a disconnected set of Morse code, dots and dashes.”
One detail drifted in the retelling. Popular versions, including the Heaths’ NPR interview, give “Happy Birthday to You” as an example song. It is not on the list of 25 printed in Newton’s dissertation.