Multiple Rhythm Skills

Figure from Tierney & Kraus, 2015.

It’s a rainy Monday night and I’m giving Nicola her weekly lesson on the grand piano in the sanctuary of the church.  She’s a reticent girl with an engaging, shy smile, who practices consistently and plays well.  In particular, she has an impeccable sense of rhythm, always performing her pieces with accurate and consistent timing. 

Nicola is working towards her RCM Grade 4 exam, so we take some time in the lesson to practice for the ear-training requirements she will face.  She correctly names intervals and chord qualities as I play them, and flawlessly copies back a short melody at the keyboard.  But when I turn to the rhythm clap-backs, her face falls and she gets a worried wrinkle in her forehead.  We both know that this is her weak spot.  I count in and then play a three-bar melody for her, emphasizing the strong beats to help her maintain a sense of meter.  I encourage her to tap along silently as I play the tune a second time.  Then it’s her turn to clap the rhythm back to me.  She claps the first measure correctly, but falters in the second measure and just stops.  She clearly has no idea what comes next.

I never could quite make sense of why this is so difficult for her.  Her sense of rhythm is fantastic, but clap-backs stump her every time.  She just can’t keep the rhythm in her head long enough to clap it back.  So when I saw a research paper entitled “Evidence for Multiple Rhythmic Skills”, I immediately thought of Nicola and was drawn in.

The paper, published in PLOS ONE in 2015, comes from the lab of Nina Kraus, who has done a lot of work looking at how musical training affects language development in children, and in particular how it affects reading skills.  Research has shown a link between rhythm skills and reading ability, and so it seems like it would be important to understand what we mean by “rhythm skills”.  Are all rhythm-related abilities grouped together in the brain so that if you’re good at one rhythm task you’ll be good at another?  Or can rhythm skills be divided into different groups that rely on different brain networks?

To answer these questions, Tierney and Kraus tested 67 volunteers on four different rhythm tasks.  In the first, the volunteers simply had to tap along (on a conga drum) to a metronome, and the researchers kept track of how closely the tapping matched the metronome.  In the second task, the volunteers again had to tap to a metronome, but this time the tempo was variable, so they had to adjust their tapping to the changing speeds.  In the third task, the volunteers were presented with a repeating rhythm, and had pick up the rhythm and tap along with it.  And the fourth task was similar to the rhythm clap-backs my students have to do:  the volunteers heard a rhythm and had to tap it back.

The researchers looked for correlations between the tasks.  If people’s performance on two tasks is correlated, it means that when people are good at one, they are usually good at the other. The researchers present this type of data as a scatterplot, with each dot representing the performance of an individual person.  If the points are fit by a diagonal line, this shows a positive correlation.

Figure from Tierney & Kraus, 2015

It turns out (as you can see in the figure above) that performance on the metronome tapping and tempo adaptation tasks was correlated.  The researchers conclude these are both based on the same skill of beat tapping.  The third and fourth task, tapping along to rhythms and remembering rhythms were also correlated, both based on rhythm memory skill.  But there wasn’t any real correlation between the two groups of tasks.

The researchers state their conclusions pretty clearly:  “These results support the theory that there are multiple dissociable rhythm skills, but do not support the existence of a single overarching rhythmic competence or ‘rhythm IQ’.”

This means that it’s actually completely reasonable for Nicola to have a good sense of beat and to be able to play rhythms well in her pieces, but have problems with rhythmic memory.  The two are based on completely different rhythm skills.  And what that means for me as her teacher is that I need to focus on practicing musical memory with her, and not try to improve her clap-backs by working on other types of rhythm tasks.  It’s a mistake for me to think of rhythm as one thing, and then just have in mind that Nicola needs help with rhythm, when in fact most of her rhythm skills are excellent.  So I’ll be working specifically on rhythm memory with her – practicing formal clap-backs as well as simple “repeat after me” exercises, and looking for patterns in the rhythms that she can grab on to.

Reference:

Tierney, A., and Kraus, N. (2015). Evidence forMultiple Rhythmic Skills. PLOS ONE 10, e0136645.

 

The Happy Song

Music psychology research at Goldsmiths, University of London has led to concrete results:  “thefirst song scientifically tested to make babies happy.”  While of course nothing is guaranteed -- for instance if your child is miserably teething, it’s entirely possible that nothing will make him happy -- thousands of parents gave their input as to the sounds that make their babies happy, and then 56 children were tested on their responses to different versions of the song.

Babies cannot tell us in words whether they like a piece of music, but scientists were able to gauge their reactions based on heart rate, facial expressions, and the sounds and movements the babies made while listening to the music.  One of the responses that was not measured was brain activity, maybe because hooking a baby up for an EEG is a big effort, and maybe because there aren’t well-validated EEG signals of infant happiness to compare with. 

But on the same day that “The Happy Song” showed up in my news feed, I also saw this post:  “The only way an algorithm can tell if you really like a song is by scanning your brain.” It reports on a small-scale mobile EEG system designed to assess how well people like a piece of music – hook it up to your computer and you would never need to hit “like” again.  It would be interesting to take a mini-EEG system like this, test babies’ responses to the Happy Song, correlate the EEG responses with the physiological and behavioural responses, and then have a neurological-based system to test what music the babies like.  But then again, babies’ smiles and laughter are pretty good indicators too.

You can listen to The Happy Song on Youtube (and below).  More details at soundofhappy.com.

Finger movements and tension

Try this: hold up your hand with your fingers extended, and then turn it so you’re looking at it side-on, with all your fingers lined up. Now bend your middle finger, trying to keep the others standing straight up. What you probably see as you move your middle finger is that your ring finger also moves out of place, no matter how much your try to keep it still. Your index finger probably moves a little too. Don’t get too stressed if it’s hard to move just your middle finger: our fingers are designed to move together. The thumb moves quite independently, but when we move each of the long fingers, other fingers also try to move.

When flexing one finger, the other fingers move out of place too.

There are two main reasons that this is true: first, each finger is connected to adjacent fingers by skin webbing, tendons, and muscle fascia, so that when we move one finger, it pulls on its neighbours. The second and more relevant reason is that our muscle control of our fingers is not completely separate.

You might think that motor control of our fingers works like this: a certain area of our brain is responsible for each finger. When that part of the brain is active, a message gets sent to the muscle responsible for that finger, which causes that finger to move. In this simple scenario, there is a straight line connection between 1 brain area, 1 muscle, and 1 finger. Unfortunately, this is not how finger control works.

The neurons that send motor commands to our finger muscles are located in the hand area of the primary motor cortex. But there is not a separate area for each finger. Studies looking at which neurons control which finger movements have found that the neurons that control the separate fingers are all kind of jumbled together. Also, a lot of the neurons that were studied were found participate in the control of more than one finger.  

This idea of mapping neurons onto finger movements gets even more complicated when you look at the muscles that move our fingers. The muscles responsible for flexing (bending) and extending (straightening) our fingers are located in our forearms, and connect to the finger bones through tendons which go through our hands. But there are not separate sets of muscles for each finger.

In fact, there are only two muscles that control flexing the four long fingers: the flexor digitalis profundus and the flexor digitalis superficialis. Each of these muscles has four tendons, one connecting to each of the long fingers of the hand. The muscle has different sections (known as muscle bellies) that each primarily activate one finger, but they are not completely separate, and they also often contract together, since the neurons that activate the muscles don't act independently either.

 

Similarly, to extend the fingers, there is one main muscle:  the extensor digitorum communis, involved in extending all four long fingers. There are also two smaller muscles:  the extensor digitali minimi (extends the little finger) and the extensor indicis (extends the index finger).

If we don’t have separate muscles controlling each finger, how do we move them independently?   The most likely possibility is that we move our fingers individually due to the combined action of more than one muscle, each of which has different amounts of control over each finger.  This conclusion comes from the lab of Marc Schieber at the University of Rochester, who showed in 1995 that when monkeys move their fingers individually, more than one muscle is active, and the amount of muscle activity in each muscle is different for the movements of each finger. 

In other words, when we try to move one finger independently, we don’t just contract a muscle to move that finger, we also have to contract other muscles to prevent the other fingers from moving. For example, raising the ring finger while keeping the middle finger still is difficult, because these fingers not only share a common extensor, but they are also joined mechanically. In order to raise just the ring finger, you need to activate the flexor going to the middle finger (in order to stabilize it), and at the same time activate the common extensor. It’s also really handy to extend the little finger at the same time, since this will pull on the ring finger and help it extend. See how complicated that is? No wonder moving our fingers individually is difficult.

Also, no wonder we can build up a lot of tension in our hands while playing musical instruments. It’s very common for children to play with their hands very tense. By maintaining activity in both the flexor and extensor muscles of the fingers, they can stabilize their finger joints and prevent unwanted movement. This strategy of co-contraction does work, up to a certain point. The problems very quickly outweigh the advantages: with too much tension in the hand, moving each finger is more work, and therefore quick and fluent movements of the fingers are impossible.

Here is a video of a young boy whom I teach who clearly has excess tension in his hand.  Notice how his fifth finger is extended as he plays.

 

This child’s problems with tension get worse as he tries to increase the tempo of his pieces. He is absolutely unable to play fast passages. This is typical of students with tension issues. Worse, excess tension leads to fatigue, pain, and eventually injury. Obviously, this situation is something to be avoided.

What’s not obvious is the best way to help students who have too much tension. When I do an on-line search, most of the advice (as in this article) is to re-align body and hand position, and then play simple exercises while focusing on mental awareness of tension in the hand, wrist, and arm. 

The good news is that our control over individual fingers is not set in stone:  we can learn to use different muscle strategies to move our fingers independently (as suggested in Winges & Furuya, 2015; Semmler et al.,  2004). This is part of musical training:  all those Hanon exercises for the piano (and Moyse studies for the flute, etc.) are designed to help us learn to efficiently control our finger muscles so that we can move fluently between different notes.

If you’ve had success in minimizing hand tension (either for yourself or your students), I’d love to hear about it in the comments.

References:

Schieber, M.H. (1995). Muscular production of individuated finger movements: the roles of extrinsic finger muscles. J. Neurosci. 15, 284–297.

Schieber, M.H. (2002). Motor cortex and the distributed anatomy of finger movements. Adv. Exp. Med. Biol. 508, 411–416.

Semmler, J.G., Sale, M.V., Meyer, F.G., and Nordstrom, M.A. (2004). Motor-unit coherence and its relation with synchrony are influenced by training. J. Neurophysiol. 92, 3320–3331.

Winges, S.A., and Furuya, S. (2015). Distinct digit kinematics by professional and amateur pianists. Neuroscience 284, 643–652.