No one knows for sure where this myth originates from. A popular theory has it that the journalist Lowell Thomas helped spread the myth in his preface to Dale Carnegie’s blockbuster self-help book How to Win Friends and Influence People. Thomas misquoted the brilliant American psychologist William James as saying that the average person specifically “develops only 10 per cent of his latent mental ability.” In fact James had referred more vaguely to our “latent mental energy”. Others have claimed that Einstein attributed his intellectual giftedness to being able to use more than 10 per cent of his brain, but this is itself a myth.

Another possible source of the 10 per cent myth is neurosurgeon Wilder Penfield’s discovery in the 1930s of “silent cortex” – brain areas that appeared to have no function when he stimulated them with electricity. We know today that these areas are functional.

There is no truth to the idea that we only use 10 per cent of our neural metter. Modern brain scans show activity coursing through the entire organ, even when we’re resting. Minor brain damage can have devastating effects – not what you’d expect if we had 90 per cent spare capacity. Also, consider the situation when neural tissue representing a limb is rendered redundant by the loss of that limb. Very quickly, neighbouring areas recruit that tissue into new functions, for example to represent other body regions. This shows how readily the brain utilises all available neural tissue.

For many people, the 10 per cent myth sounds both feasible and appealing because they see it in terms of human potential. Many of us believe that we could achieve so much more – learning languages, musical instruments, sporting skills – if only we applied ourselves. It’s easy to see how this morphs into the shorthand idea that we use just 10 per cent of our brain’s capacity or potential. While for the people who repeat this myth, it’s probably true, the rest of us happily use all of our brains.