Pulse and entrainment

Hi, in this video we’ll be talking about pulse in music and a bodily process we call entrainment. If you watch people experience music, you often see they nod their head or tap their feet. Usually this follows a certain pulse in the music. Rhythmic music have several pulses, faster or slower. But if I ask you to tap your finger to the beat, this usually ends up with what we consider the main beat or the main pulse of the music. But how do we find the pulse? In the typical dance music track, the task is not too hard.

The bass drum often, as you hear here, comes repeatedly with equal duration between the beats, and these sounds are interpreted, often unconsciously, as the main pulse.

In other music, the task may be more difficult, and you may struggle to find the pulse. Also if you play instruments together with others. We search for sounds that mark starting points. We search for accentuations. We search for downbeats and upbeats. But why has this anything to do with music and movement? Well, we often use our body to find the pulse. The tempo of a dance track is usually between 120 and 135 bpm. BPM means beats per minute. So 120 BPM means two bass drum sounds per second. Why is this often used in dance music? Human movement studies have shown that we typically walk with the frequency of two steps per second, independent of gender, age, height, or weight.

There have also been music perception studies indicating a clear preference for musical tempo of two beats per second. So this range is a good tempo for walking, for dancing and the music is formed according to bodily movement. The human ability to synchronise to music is unique. We can nod our head or tap our feet to the beat and we call this process entrainment. This is a concept that describes a relation where one pulse influences another. It dates back to the 17th century when the Dutch mathematician and physicist Christiaan Huygens discovered that two pendulum clocks placed on the same surface always will end up moving in synchrony, in the same phase.

The oscillation is transferred from one pendulum to the other through the surface. Similarly, we as humans, adapt to the rhythmic oscillation of, for example, a fellow musician. When we’re listening to music, the rhythmic oscillation of the external source can entrain certain bodily processes. Head nodding, foot tapping, body bouncing, are visual demonstrations of this process. But what happens on the inside is still an active research topic. Mari Riess Jones believes that our attention to towards rhythm in music oscillates. So that we have attentional peaks at important points in the music. Points or specific sounds or accentuations, marks, starting points of a rhythmic phase. These are called attractors. The bass drum sounds in a dance music track works as such an attractor.

This way of describing an entrainment process is in line with the view that sees our cognition as a dynamic system where many ongoing processes interact with no start points, no endpoints, no inputs, no outputs. And this view questions a more traditional cognitive science approach thinking about the brain as a computer. Rather, it sees the body as an integral part of our cognitive system, and the entrainment process seems even more convincing when bodily movement is introduced.

Daniel Schneck and Dorita Berger explain how rhythmic in music correspond with our muscular behaviour. “Rhythmic pulsation embodies a consistent symmetrical balance of energy output, of fall and rebound, of tension and relaxation. Rhythmic vibration in music involves the same steady stream of force, rest, force, rest, of systematic strong and weak impulses of alternating flexion, release, and extension as in the case for paired and coupled muscular behaviour.” So moving to the rhythmic pulse of music seems like a very human thing to do connected to how our muscles behave and to basic human abilities like walking, running, jumping, et cetera.

If you have ever seen small children dance or bounce up and down to music, sometimes even before they can walk, this also proves this point.

Christian, you have a daughter. How old is she? She’s ten months. Ten months. And does she already interact with music in some ways? Absolutely. She starts swaying back and forth whenever we play any kind of music or sing to her. Oh, yeah? Is it synchronised to the music, or–? Yeah, most often it’s synchronised to a certain extent, at least. Do you think she’s imitating you, or–? No, maybe she’s trying to imitate something in the music, but and it’s not something that I taught her, at least. It’s something that seems to be just there. She moves to the music somehow. She feels the pulse then somehow. Yeah, it seems like it.

So it’s kind of a human ability then, to move to music at this early age. Absolutely. She started this several months ago, listening to this book that has a drum kit that plays music. That’s quite fascinating. Yeah.