Ever find yourself walking down the street with a friend and your steps begin to line up? Just like Little Mix in the picture.
Humans have this unique ability to move in time with a rhythm. Whether it's the footsteps of a friend, clacking on a keyboard, or the beat of a song. We naturally begin to groove with the "external stimuli" (to give it its technical term).
It's thought that this ability helps us mimic others. This might come in useful when we're trying to learn from them, bond with them, or simply keep up with them as we walk down the street. After all, walking naturally produces a fairly consistent rhythm.
However, it turns out that this special ability to move in time with the rhythm might not be as unique to humans as we thought. A new set of studies in chimps have found that they also have this innate ability.
Discovering chimps got the groove
So how did scientists find out that chimps had this ability to move in time with the music? Well, they were curious as to whether chimps had this ability. So they decided to test it.
They gave chimps a keyboard and trained them to repeatedly tap two keys on it. Then they started playing a beat. Sure enough, one of them (called Ai) began to change the frequency of their tapping until they were doing it in time with the beat. Yet only 1/3 chimps began to respond to the beat. Might the results of this investigation simply be a fluke? So the researchers began to conduct additional tests on Ai to confirm that they really were being influenced by the rhythm.
This involved trying to distract them with a rhythm. Rather than simply playing a beat and seeing if Ai moved in time with it, they measured Ai's natural rhythm. They then began playing beats just off that. The logic being that if Ai was simply matching that initial beat by chance then they should be unaffected by these other beats. However, if it really was influencing them then they should be "distracted" by these slightly off rhythms and start tapping at a slightly off rate.
Sure enough Ai - along with several humans they conducted this same experiment on - altered their behaviour to match the distracting rhythm; even when they'd already started tapping at their preferred pace. This confirmed that at least some chimps have this innate ability to synchronise their activities with other rhythms. Just like humans.
Not every chimp they examined displayed this ability; but then not every human did either.
So what does this mean?
When humans mimic the rhythm of other things it's often thought to help us learn. If we can naturally copy the speed an action is performed then we will be much better at learning how to do that action. Chimps also engage in social learning, so this ability might also help chimps in the same way.
However, the authors identify another possible benefit chimps derive from this ability: bonding. Being able to move in time with others may enhance empathy between them and reinforce the idea that they're part of the same group. In turn, this encourages bonding between these individuals. Although humans might benefit from the learning side of rhythm; it also helps us bond too. When we move in synchronicity with others they're more likely to co-operate with us.
So more research is needed to help identify which of these many factors may have influenced the evolution of this trait. Which is the other interesting thing about this research. Since chimps also have this ability this strongly suggests it was present in the last common ancestor of humans and chimps. Hence how we were both able to inherit it. This means for at least 7 million years hominins have been tapping away in time to the beat.
I bet Lucy had some killer dance moves.
References
Hattori, Y., Tomonaga, M., & Matsuzawa, T. (2013). Spontaneous synchronized tapping to an auditory rhythm in a chimpanzee. Scientific reports, 3.
Hattori Y, Tomonaga M, Matsuzawa T (2015) Distractor Effect of Auditory Rhythms on Self-Paced Tapping in Chimpanzees and Humans. PLoS ONE 10(7): e0130682. doi:10.1371/journal.pone.0130682
