We’ve all been there, driving down the street listening to music while moving our fingers to the rhythm, sitting in a concert hall tapping our toes to the music, working out in the gym making our reps or steps match the background beat around us. I’ve caught myself falling into step with random music coming out of a shop or coffee house just by simply walking past. We call this rhythmic entrainment, the tendency to sync up with the beat around us.
That word, entrainment, has several different meanings. What we are talking about closely lines up with its definition in the world of physics. Entrainment tells us that two objects moving together use less energy than those moving opposite or differently. It’s the tendency of independent systems to sync up, to start to move in sympathy with one another.
There’s a fascinating video on youtube that displays this tendency very well. On the screen are 32 identical metronomes, the mechanical type with the swinging arm. All of them are set to the same tempo on a table that can float and move freely. The metronomes are started in a random order and begin to mark time. At the beginning it’s chaos as each one seems to be in its own world. However, over time, the swinging motion is picked up by the table and gradually the metronomes begin to sync up, affected by one another. It only takes a couple of minutes before they beat as one. We call this mode-locking and it’s not just something we see with metronomes. Many biological systems react this way as well; it’s an easy way to see how pacemakers work with the human heart.
When you tap your foot to the music we call that beat induction. It’s a pulse activated inside of you triggered by something outside. Beat induction allows us to sync up as we clap, play instruments together, sing and dance. We can feel the pulse, sensing when it speeds up and slows down, stops and starts. And before you say, “big deal” or “so what?” understand that we are only primates who can do this.
Neuroscience is trying to figure out why rhythmic entrainment seems so innate to the human mind. The gradual audio-motor evolution hypothesis, proposes that over time the ability to move in sympathy to an outside rhythm was beneficial to our species. Perhaps it has something to do with the use of language and learning, which is why some birds seem to have this same skill. Also, perhaps the social, societal and communal connection that this entrainment allows has led to it be a part of who we are as a species.
As you can tell there is a lot that we don’t know about this phenomenon. As music psychologist Lauren Stewart of Goldsmiths, University of London stated, "The question of why music is found in every known human culture is a longstanding puzzle. Many argue that it is an adaptive behavior that helped our species to evolve. But equally plausible is the possibility that it emerged as a by-product of other abilities -- such as vocal learning."
The Strong Institute in Santa Fe, New Mexico champions a music therapy program called Rhythmic Entrainment Intervention. They use recorded rhythms to stimulate the brain and nervous system to improve neurobiological disorders. They contend that we can alter our state of mind through the use of rhythmic entrainment.
In the next episode we’ll take this idea a step further as we talk about brain entrainment. But till then we’d love to hear what you think. What has this subject triggered in your mind? Comment below and let us know. We'd love to hear from you.
Timeline is an exploration into the development of Western music.