Panta rhei. Everything flows. This aphorism was supposedly coined by Heraclitus nearly 3,000 years ago. It was his belief that nothing remains as it is; the only constant is change. Most of us would agree unreservedly with this idea. After all, we see the world changing every day as we go about our lives – and that’s not only true of everything, but of everyone, too.

Children become adults, eloquent professors turn into care-dependent dementia patients, high-school dropouts transform into dotcom billionaires and wallflowers grow into showstopping stars. But we have a tendency to “freeze-frame” our fellow human beings in certain situations. We speak of born orators, artists, or thinkers, but also born losers and born criminals.

We are unable to believe psychopaths can ever become valuable members of society, and we demand they be locked up. We call for a “humane” end for those in a persistent vegetative state; we’d like to put an end to their “suffering” by switching off the machines their lives depend on. We harbour the fatalistic assumption that some people just can’t change, and so there can be only one solution for dealing with them: they must somehow be prevented from becoming a burden on society or from hurting themselves and others. Just don’t let them disturb the peace, that’s the main thing.

No one is frozen forever in their behaviour patterns, or immune to any attempt to influence them

Friedrich Nietzsche said that human beings, with the conceptual tools available to them, were doomed to fail repeatedly to express the idea of “becoming”. He argued that this was the case because, although words could to some extent at least be used to capture that which is, they are not capable of capturing what will be. It may be that this deficiency explains why we repeatedly hear talk of immutable character traits and personal characteristics.

In contrast I believe in neuroplasticity: the virtually limitless capacity of the brain to remould itself, and I argue that no one is frozen forever in their behaviour patterns, or immune to any attempt to influence them.

Humans have been both blessed and cursed with an almost boundless willingness to learn – it is a boon and our doom. We can go from being a loving family man to an inconceivably cruel mass murderer, and then back again to an upstanding citizen. These changes reflect nothing other than “perfectly normal” products of the enormous plasticity of our brains.

Various experiments have shown that observational learning – learning that occurs through observing the behaviour of others – controls one of the most efficient learning processes, and that it is firmly embedded in specialised cells in the cerebrum.

There is one problem with this mechanism: our brains “mindlessly” copy anything that promises success and effect. This is why we must strive to maintain a democratic context to our lives, so that our plastic brains do not seduce us into acts of denunciation, murder and slaughter as has so often been the case in history.

When such behaviours are rewarded – as they usually are in undemocratic, dictatorial systems – the brain will principally conform to those patterns. The good news is that our brains are open for change; neuroplasticity opens up endless possibilities. If we experience a positive effect achieved through compassion and respect, those behaviour patterns will become stabilised within us, and will recur again and again.

Your Brain Knows More Than You Think by Niels Birbaumer is published by Scribe at £14.99. To order it for £12.74, go to bookshop.theguardian.com