Sometimes upon hearing a song, one feels an almost involuntary need to start to move to it. Is there something about a pulsing dance beat that transcends reason and makes you want to gyrate to the beat? Is this quality universal to humans everywhere, transcending not only reason but also cultures and language? My most recent personal discovery of this cross-cultural foot-tapping effect is the house beat of the Amsterdam-based artist Born to Funk put to work on Danish/Tanzanian hip hop artist Mzungu Kichaa's song "Oya Oya".

So now that you're started to move to that beat, what does science have to say about this? Daniel Cameron, a Ph.D. student at the University of Western Ontario who performed this research for his Master's degree at Goldsmiths University of London, explained to me how his research relates to the question of how a beat seems to make us move. He started with the fact that people all over the world seem to universally move to the beat of music, whether in complex ways like dancing, or simple forms like clapping or tapping their feet. But how can you break this behavior down into something you can study scientifically?

Enter a technique called transcranial magnetic stimulation or TMS. This technique uses an electromagnetic field to induce an electric current through a person's skull that can activate a targeted area of the brain. In the case of a previous study by Wilson and Davey in 2002, TMS was used to stimulate the ankle muscle-controlling part of the motor cortex in the brain. So when the electric current from TMS activated the part of the motor cortex that controlled the ankle muscles, the subjects in the study tapped their feet involuntarily. While stimulating the motor cortex, it is possible to measure the motor evoked potential or MEP, which, put simply, serves as an electrical recording measuring how much a muscle is moving. In this Wilson and Davey study, playing music with a strong beat while stimulating the brains of the research subjects to move their ankles and thus their feet to the beat effected the MEP, or muscle response to the electrical stimulation of the TMS.

Cameron wanted to build on this link between the beat of music and ankle-tapping MEP in his study, so he selected a few different pieces to play for his subjects while recording their ankle-tap MEP and stimulating their brains to the beat via TMS. The simplest pieces played were just tones that had either a strong beat or a weak beat. The more complex pieces played were snippets from actual popular songs like the Beatles "A Day in the Life" and the Beach Boys "Wouldn't it Be Nice." Cameron took parts from the song with a strong beat and different parts of the same song with a weak beat in order to compare the ankle response to the pieces of music. He pulsed the TMS stimulation to the subjects' brains in time to the beat of the songs or the beat of the tone sequences while measuring the MEP response of their resulting ankle-taps.

The preliminary results of this study found that the tone sequences with a strong beat invoked a greater ankle-tap MEP response than the tone sequences with a weak beat in three out of the four subjects. This might indicate that a strong beat in music creates a bigger "innate" muscle response to music, but there was a puzzling finding of the part of the study that involved snippets from songs. Even though the tone sequences with a strong beat produced a larger ankle-tap MEP response, the song snippets failed to create a similar significant response to the beat. Cameron explained that this lack of effect could be due to subject familiarity with the songs or other issues that arise when someone hears a complex musical stimulus like a piece of music. Future studies could try to determine what went wrong with the song stimulus by breaking the songs down into pieces of stimuli that more closely mirror the tone sequences. By classifying the differences between the songs and the tone sequences, we could gain a greater understanding of what drives that foot-tapping response to a crazy (or in Swahili, kichaa) beat.

Cameron et al. "Modulation of ankle-driving MEPs by metric Strength in tone sequences and music" Goldsmiths (University of London), 171.07/JJ9

Images:

"TMS" from University of Colorado Denver Department of Psychiatry.