An age-old problem: when does the brain deteriorate?

By Eve Kirman

For students like us (and anyone really), the uncontrollable passage of time and the inevitability of getting old is never a fond prospect. To put it simply, people don’t want to be old and face all the inescapable challenges that ageing brings. What springs to mind for most people is the greater risk of disease, increased likelihood of memory loss, unwanted body changes and the prospect of loneliness. However, recently, one of these factors has been found to be prevalent much later into the ageing process than first thought.

It was originally believed by scientists that acting less and less impulsively was a marker for the beginning of cognitive deterioration, ultimately meaning that the brain was starting to slow down. As impulsivity starts to decline when individuals reach their early twenties, it was thus thought by researchers at the time that the brain steadily declines from this age. This would mean many of the undergraduates and almost all postgraduate students studying in Durham right now would have already peaked in terms of cerebral ability — a depressing notion in the least.

A few weeks ago, scientists working in Heidelberg University’s Psychology Department have concluded that cognition doesn’t actually start to slow until after we turn sixty years old. With further implication that the brain, if kept stimulated, can retain full capability for an entire person’s lifespan.

Individuals around the age of thirty had the best mental processing

The findings, detailed in the journal Nature Human Behaviour, were based on data from over 1.1 million participants from the ages of 10 to 80. This huge participant number can be attributed to Project Implicit: an online collaboration by Harvard University that collects data on implicit biases that people might hold. Participants of the project were told to categorise words into positive and negative groups as well as placing images into different racial categories. The purpose of this was to gauge the extent of a person’s association between the two fields. However, instead of looking at the racial bias the test was designed to reveal, this study analysed the data from the project in terms of each participants accuracy and speed of response in the context of their age.

From looking at this data, akin to previous studies, it was shown that average time to produce a correct response increased after the age of twenty. Thus, showing the human brain to peak at this age. However, what’s different with this particular study is that the researchers believed this figure to be warped by reasons unrelated to cognitive speed. Instead, the scientists argued that this is only the case as caution becomes more prevalent in individuals and reaction time slows after the age of twenty.

Therefore, steps were taken to analyse the data in a way that allowed these researchers to see each individual’s level of caution and motor ability when choosing their answers. It was after this machine learning technique that they could show data that led them to their overall conclusions. In particular, they found participants between the ages of fourteen and sixteen were quickest in their responses while individuals around the age of thirty had the best mental processing ability. Furthermore, crucially, it was deciphered that participants made less and less mistakes as they aged — up until the age of sixty.

The head researcher, Mischa von Krause, told U.S. and World Report of how these findings disprove previous ideas detailing that the “research now shows that this slowing [in response time] is not due to a reduction in cognitive speed”. For clarity in the differences between previous studies findings, Von Krause told the magazine that the slower reactions can be explained “by the fact that people become more cautious in their decisions with increasing age, i.e., they try to avoid mistakes,” while “at the same time […] the motor processes […] slow down with increasing age.”

It is thought that these findings, while significant in their own right, hold significance also in the broader context of psychology. Psychologist Dr Hartshorne of Boston College told The Guardian that this machine learning technique of reviewing data could urge psychologists to review other previous findings that were based purely on response times. Thus, while we can be certain that we’ll all age with time, we perhaps cannot be completely certain of the psychology underlying our ageing.

Photo: Robina Weermeijer, Unsplash

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