If you ever fear that you are already too old to learn a new skill, remember Priscilla Sitienei, a midwife from Ndalat in rural Kenya. Having grown up without free primary school education, she had never learnt to read or write. As she approached her twilight years, however, she wanted to note down her experiences and knowledge to pass down to the next generation. And so, she started to attend lessons at the local school – along with six of her great-great-grandchildren. She was 90 at the time.

We are often told that “you can’t teach an old dog new tricks” – that the grizzled adult brain simply can’t absorb as much information as an impressionable young child’s. Many people would assume that you simply couldn’t pick up a complex skill like reading or writing, at the age of 90, after a lifetime of being illiterate.

The latest studies from psychology and neuroscience show that these extraordinary achievements need not be the exception. Although you may face some extra difficulties at 30, 50 – or 90 – your brain still has an astonishing ability to learn and master many new skills, whatever your age. And the effort to master a new discipline may be more than repaid in maintaining and enhancing your overall cognitive health.

Wax tablets

But there hasn’t always been such an optimistic view of learning brand new skills from scratch as a grown adult.

The prevailing, pessimistic, view of the ageing mind can be traced back to the Ancient Greeks. In his treatise De Memoria et Reminiscentia, Aristotle compared human memory to a wax tablet. At birth, the wax is hot and pliable, but as it cools it becomes too tough and brittle to form distinct impressions – and our memory suffers as a result.

Millennia later, scientists’ understanding of the brain appeared to echo this view. Neuroscientists even use a word to describe the brain’s adaptability – neuroplasticity – that directly recalls the malleable wax of Aristotle’s “tabula rasa”, and as we age, we were thought to lose much of that plasticity.

Childhood, in particular, was thought to be the “critical period” to make those impressions. By the end of the critical period, the brain’s circuits begin to settle, making it far harder to learn many complex new skills.

Compelling evidence for this theory appeared to come from people learning a second language. Young children brought to a new country seemed to find it far easier to reach fluency than their older siblings or parents, for instance.

Yet a closer look at the data paints a somewhat rosier picture. Analysing the census records of immigrants, Ellen Bialystok at York University in Toronto showed that the immigrants fluency appeared to decline very gradually with the age at arrival, rather than a drop off a cliff predicted by a critical period. And that may have been partly due to the fact that the children simply had more opportunities to master the language, with the support of schools and their classmates. Or perhaps children are simply less inhibited and aren’t so scared about making mistakes.

Just consider the case of Aleksander Hemon. Originally from Sarajevo in then-Yugoslavia, he found himself stranded in the US on the outbreak of the Bosnian war in 1992 – despite having little command of English. “I had this horrible, pressing need to write because things were happening. I needed to do it the same way I needed to eat, but I just had no language to write in,” he later told the New York Times. And so he set about embracing the language on the streets around him. Within three years, he had published his first piece in an American journal, a path that eventually led to three critically acclaimed novels, two short story collections, a book of autobiographical essays, and a MacArthur Genius Award.

Hemon’s profound mastery of expression should have been near impossible if language acquisition had to fall within a critical period for us to achieve true fluency. But his sheer determination and the urgency of the situation fuelled his power to learn.

Admittedly, children may still find it easier to master certain skills, particularly those that revolve around the fine-tuning of our perception. A linguist may struggle to exactly match a native’s accent, while a new musician may never be able to acquire the refined perception of “absolute pitch” shown by stars like Ella Fitzgerald or Jimi Hendrix. But as Hemon shows, you can still be an award-winning novelist without sounding like a native, and many accomplished musicians do not have perfect pitch. Amazing progress is still possible in many different fields, and adults may find that they can make up for some of the deficits with their greater capacity for analysis, self-reflection – and discipline.

The scientific literature is now dotted with case studies of older adults performing amazing mnemonic feats, including a septuagenarian who learnt to recite all 10,565 lines of John Milton’s Paradise Lost for public performance. Such extended neuroplasticity also seems to be reflected in more recent studies of the brain’s anatomy, revealing that the adult brain is far more fertile than expected, and more than capable of sprouting the connections necessary for profound learning.

Keeping in shape seems to be particularly important for maintaining that plasticity, as exercise helps to release a flood of neurotransmitters and hormones that are known to promote the growth of new brain cells and synapses.