It is rather surprising how often psychologists inadvertently come up with poetic terms to describe their discoveries. One such term in neuroscience is, ‘sensory gating’. When a human hears a sound their brain responds rapidly, peaking at around 50 milliseconds (P50). The minute electrical currents generated by that response can be measured and plotted onto a graph. The graph looks like this:
When the same sound keeps repeating, with a short gap of about half a second between, the height of the P50 peak progressively reduces, resulting in a flattening of the response curve. It is a strangely counter-intuitive concept: the higher the level of sensory gating, the flatter the response curve.
‘Sensory gating’ is a kind of habituation effect. Some writers link this phenomenon to the theory of ‘fight or flight’. The brain, they claim, makes an involuntary response to any sound, evaluating it as a potential threat. When we hear the same sound several times, the curve begins to flatten, and the brain no longer perceives the sound as threatening.
Lower sensory gating
Although the vast majority of people exhibit similar levels of sensory gating, a small minority display reduced levels. Instead of becoming habituated, they respond to repeated instances of the sound with a similar intensity. Schizophrenics are one social group that have particularly low sensory gating. Their elevated anxiety is thought to constantly trigger the ‘fight or flight’ response. There is, however, another group of people who have also been shown to have lower levels of sensory gating: musicians.
I came across all this when, as a psychology technician. I was trying to learn how to implement electroencephalography (EEG) experiments. An ‘auditory response test’ was the simplest EEG experiment that I could try to do.
Improvisation
It was when I tested myself that I received a surprise. It seemed that I had a surprisingly low levels of sensory gating. I began to wonder if this was linked, not to any unacknowledged schizophrenia, but to my practice regime as a musician. Instead of practicing the scales, arpeggios or jazz patterns I should probably do, I often just wear headphones and improvise along to whatever I am hearing. You could call it intensive ‘ear training’, done on a daily basis.
I started to wonder: does improvisation, in particular, develop a specific attentiveness to sound, even to the extent that it can supress sensory gating? Many orchestral musicians play written music and never improvise. Improvisers, by contrast, rely solely on their ability to make an instant response to sound. Classical musicians could counter that they are equally responsive to the details of sound. They might highlight how they modulate their volume, tone, articulation and expression to the requirements of the music. Would sensory gating be lower amongst improvisers than amongst orchestral musicians?
Dancers
I haven’t found any studies that have examined this. I suspect that it might be true, but only a detailed, large-scale experiment could conclude that it was. A study of dancers, musicians and ‘lay people’ comes close. Dancers display the kind of reduced sensory gating that one might expect from improvisers.
Functional Growth
Hercule Poirot boasts about the number of ‘little grey cells’ associated with his powers of deductive reasoning. It is interesting that musicians can make a similar claim for their craft. Professional musicians have enhanced ‘functional’ growth in those areas of the brain associated with listening and dexterity. Did this ‘growth’ develop as a result of practice regimes, or did it precede and condition their musical abilities? I can’t help wondering if we would discover a slightly different distribution of ‘little grey cells’ amongst dedicated improvisers?
What hapens next?
For a time, I contemplated the idea that I might do this research myself: after all, I know so many improvisers. However, time passed and I eventually stopped working as a psychology technician. So, if someone stumbles across this post who would like to discover the answer to these questions, but also has access to the appropriate research equipment, please do let me know. I suspect that volunteers would not be hard to find.