Have you ever found yourself lost in conversation when walking next to someone, but then you look down and suddenly you notice that your footsteps are totally in sync? When they step with their right foot, your right foot is already moving to match the pace, in total coordination, without even thinking about it!
Well, falling into step with someone is one of the most obvious examples of a concept called entrainment.
Oxford English Dictionaries defines entrainment like this:
Entrain (Verb) [with object]
Biology (of a rhythm or something which varies rhythmically) cause (another) gradually to fall into synchrony with it.
In simple terms, it describes the way the body gradually syncs with either a biological or external rhythm.
The key thing about entrainment is that it can happen unconsciously. For example, when dancing you might be trying to move to the beat, but you might not realise that your breathing rate will also be syncing up.
Here are just some of the ways the human body can respond to rhythm - but let us know if you can think of any others!
While your breathing rate can be controlled (for example when singing or playing a musical instrument), most breathing is involuntary. Slowing your breathing rate is something that lots of people try to help reduce stress, but your breathing rate is constantly adapting to external rhythms - especially audio.
For example, way back in the 1920s research C.M. Diserens noted that music had an effect on breathing rate. He is quoted to say that “in general respiratory rhythm follows that of the music.”
Since then, more and more has validated his work. In 2005 researches in Italy studied the effect of different styles and tempos of music on cardiovascular and respiratory control in both musicians and non‐musicians and they found that breathing frequency not only increased as music got faster, but also it increased proportionally to the tempo of music.
So next time you’re listening to music, see if you can spot your breathing rising and falling to match the beat!
Heart rate is another biorhythm that responds to music, although this has a lot to do with its close link with breathing rate. Faster breathing rates tend to correspond with faster heart rates, and so fast music can cause both to rise. The link between breathing rate and heart rate is perhaps best demonstrated by a 2013 study published in the journal Frontiers in Psychology which showed that choir singers not only harmonize their voices, but they can also synchronize their heartbeats.
Dr Bjorn Vickhoff, from the Sahlgrenska Academy at Gothenburg University, said:
"The pulse goes down when you exhale and when you inhale it goes up.
"So when you are singing, you are singing on the air when you are exhaling so the heart rate would go down. And between the phrases you have to inhale and the pulse will go up.
"If this is so then heart rate would follow the structure of the song or the phrases, and this is what we measured and this is what we confirmed."
But the heart rate also responds to other biological rhythms. For example, the heartbeats of a mother and baby will synchronize with one another when they interact closely, and similar effects have been observed in couples.
Recent research also shows that when an empathetic partner holds the hand of a woman in pain, their heart and respiratory rates sync and her pain reduces - perhaps something to share with any friends you know currently expecting a baby!
But it’s not just heart rate that is affected by being close to someone else. Researchers also found that if you sit a couple face-to-face and ask them not to talk, just staring at each other for fifteen minutes is enough to get their levels of skin conductance and heart rate to sync up.
Skin conductance (as defined by MIT) is “the phenomenon that the skin momentarily becomes a better conductor of electricity when either external or internal stimuli occur that are physiologically arousing” - that is, the response of your eccrine glands (the glands responsible for keeping you cool) to different stimuli. These glands are found all over the body, but especially the palms of the hands and soles of the feet. While they react to things like stressful situations (and are in fact one of the metrics used to measure stress in the lab), the fact that they react to other people’s biorhythms really demonstrate just how responsive your body is to external rhythms.
This isn’t something you’ll be able to try at home unless you happen to have access to a lab, but it’s worth thinking about the next time you find yourself sat opposite someone on a long journey!
Here at doppel we’re especially interested in not just the physiological responses themselves, but also how these responses affect how you feel.
Your brain and body are in a constant feedback loop and changes to things like your heart rate and breathing rate are intrinsically linked to how you feel. For example, research shows that slower tempos result in calm and positive emotional states while we associate fast rhythms with emotional states such as joy, excitement and surprise.
So next time you notice yourself falling into step with someone, have a think about all the other ways your body can synchronize with rhythm - and how that these rhythms might even be influencing how you feel.