Does anyone really believe this?

No one seems to know exactly where this idea comes from. One possibility is that it originated from William James, arguably the first experimental psychologist, in the 1890s who had a theory of ‘reserve mental energy’. Christian Jarrett explores other possible origins of this myth in his excellent book Great Myths of the Brain[i].

The notion that we only use 10% of our brains is widely believed. In a recent survey, 43-59% of teachers from around the world reported that they thought this was true[ii]. It seems that the 10% myth persists for two primary reasons: firstly, its intuitive appeal. We would all like to believe that we have a huge reserve of untapped brain matter, and teachers would like to believe this of their pupils. Secondly, it is actively propagated in the media, including in two major films of recent years- Lucy (2014) with Scarlett Johansson, and Limitless (2011) with Bradley Cooper, in which the protagonists unlock their potentials, with dramatic results!

Actual usage of the brain

The truth is that essentially we use all of our brains all of the time (though not all neurons are firing at the same time). The advent of functional magnetic resonance imaging (fMRI), and other brain imaging techniques, have proven as much. If you’ve seen images from fMRI studies, it looks as though only small portions of the brain are active at once, but in reality this is a by-product of the way data are processed. Studies present contrasts of brain areas that are working harder (demanding more oxygenated blood) in one condition compared to another. The processed data are showing the differences between the conditions. What the raw data show is widespread ongoing activity in most of the brain at any given time; even when we sleep no area of the brain is completely inactive.

Data from imaging studies aside, the most convincing argument against the 10% theory is that the brain accounts for around 2% of our body mass but around 20% of our energy consumption, and indeed up to 60% for infants. There’s simply no way that such a costly organ could be so underused- if that were the case, homo sapiens would never have evolved brains anywhere near the size we have, let alone dominated the earth as a result of our trademark intelligence.

The brain’s potential is in its plasticity

What is true is that the brain has an extraordinary capacity for change known as plasticity. Every time we lay down a new memory, learn someone’s name, develop a new skill or even just have breakfast, our brains change. Memories are stored as patterns of activity between neurons and every time we learn something new, new connections (synapses) are formed. Over the past decade studies have traced changes in the brain as we learn new skills like juggling[iii], or touch typing[iv]. Learning new motor skills such as these in adulthood is accompanied by substantial changes in the volume of localised brain tissue. These changes correlate with duration and practice and reverse after a period without practice.

Untapped potential

The only limitation to the number of new skills we can learn seems to be the time we put into practicing them. So although it’s not true that we have untapped brain matter, the vast majority of us certainly have untapped potential. This particular neuro-myth has possibly done more good than harm in the classroom as evidence is now emerging that our beliefs about learning have a substantial impact on our progress. For example, one study in the US looked at how beliefs about learning could impact on mathematics achievement for teenagers over a two year period. They found that teenagers who were taught that intelligence is malleable significantly outperformed those who were taught that intelligence is fixed[v]. So not only is the reality of the neuroscience here much more interesting than the myth, but the more teachers, parents and children who know about it, the more potential could be unlocked! The verdict? A definitive neuro-myth.

Further resources

For further information on this and many other neuromyths see Jarrett, C. (2015). Great myths of the brain. Wiley Blackwell.

For an engaging look at this from TED, see here.

For an introduction to brain plasticity, see here.

© CEN