Sudoku probably won't save your brain. So what will?

"The perception that we reach a cognitive peak at age 20-30, and then necessarily deteriorate, is mistaken and outdated." This provocative claim was recently made by Dr. Lori Cook, head of clinical research at the Center for BrainHealth at the University of Texas at Dallas, in an interview with the BBC, following a large study she led.

In the study, which included more than 4,000 people of various ages and cognitive levels, the participants underwent a series of intensive training, the results of which, according to the article published in the journal Science Reports from the Nature group, were extremely positive.

The effect of the training was evident at all ages, and the improvement in 70 and 80-year-olds was similar to the level of improvement among young people. Healthy participants with high cognitive abilities also showed improvement following the training, which led Cook to declare that "there is no ceiling to the abilities that can be reached with brain training," or at least most of us are very far from that ceiling. "The brain is not defined by its chronological age, but by its potential," she said.

The issue of brain training is controversial, and Cook's study and its far-reaching conclusions have also sparked criticism. Nevertheless, it joins a growing body of research from recent years that supports the benefits of brain training. The question is how to perform such training correctly, what its limits are, and what the reasonable expectations from it are.

Past assumptions have given way to a new scientific consensus

The concept of brain plasticity in old age has undergone a dramatic change in recent decades. Throughout the 20th century, the prevailing theory was that children's brains are flexible and allow them to learn new skills easily, but gradually the "windows" for learning various types of skills close, and as adults, we can never reach the level we could have reached if we had started learning these skills earlier.

According to this approach, we reach our cognitive peak in early adulthood, and then we deteriorate until we necessarily reach dementia, or die sooner.

Since the beginning of the 21st century, almost all of these basic assumptions have been refuted or at least had an asterisk added to them. Indeed, there are skills that are easier to learn in childhood, but not all, and learning in old age is not impossible. And indeed, the brain becomes more fixed in adulthood, but it is not completely fixed. Brain cells regenerate more than we thought, at any age, and even into old age.

5 habits that will keep the brain healthy

1. Physical activity, especially aerobic. It is especially beneficial if you add another challenge to each workout.

2. Good sleep. Quality sleep appears in many studies as a central component in maintaining cognition.

3. Social connections. Interaction with people is considered one of the proven cognitive interventions for maintaining the brain.

4. Brain training, without getting stuck on Sudoku. Specific training improves mainly the ability being trained. Activity that involves mental flexibility, problem-solving, new learning, and stepping out of the comfort zone is preferable.

5. Caring for general health. The heart, sugar, hearing and vision, intestines, kidneys, and lungs - all these affect brain health.

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Connections between brain cells are also not as fixed as we thought. In fact, studies from the last decade have shown that the brain continues to develop deep into adulthood. It completes some of its development processes only in our 30s. The only reason this was not known is that most studies dealing with development in the 20th century simply did not examine adults.

We also learned that cognitive deterioration is not predestined for all of us and does not stem directly only from the number of years that have passed. It is related to specific diseases like Alzheimer's or various injuries resulting from lifestyle, and there are "super-agers" who will maintain impressive mental sharpness with almost no deterioration even in their old age.

Researchers have found that it is possible to influence brain competence through exercise, social connections, preventing sensory deterioration (for example, through hearing aids and glasses), and proper nutrition. All these can not only prevent deterioration but even turn back the clock a little.

There are researchers who have taken this approach one step further and argued that the brain is flexible at any age, and it is our perception of age that fixes us, and paradoxically accelerates aging. We have previously spoken with two of the leading researchers in this field, neuroscientist Prof. Michael Merzenich and psychiatrist Dr. Norman Doidge. Not all researchers have gone as far as they have - after all, it is known that in the vast majority of people, brain cells die with age, brain tissue decreases, and cognitive abilities decline, and yet, the principle of brain plasticity in adulthood has become a scientific consensus.

"An interesting study, but it has weaknesses"

And so, the question arises: how can one keep the brain flexible for as long as possible? Merzenich and Doidge, along with other researchers, believe in various types of brain training. Merzenich has a company that developed software including exercises for brain training. Doidge developed a protocol including music, flashing lights, and electrical currents under the tongue.

The current study by Cook fits into this trend. For three years, the subjects received training of several types simultaneously. Each subject performed a series of exercises every day designed to improve concentration, the ability to solve problems, and the ability to draw conclusions. They also underwent behavioral training to improve sleep, and guidance on how to use tools to reduce mental stress and increase resilience.

The measures the researchers used were holistic, meaning they measured overall brain function and quality of life instead of breaking down brain abilities into their components, as is customary in other measures. They explained that "a brain can be healthy even when the neurons are not healthy," meaning overall brain function is not always in full correlation with what we know about the physical health of the tissue.

The results of the study showed a constant improvement in the average cognitive performance of the group in the general health index, an improvement that accumulated almost linearly over the three years of the experiment. The researchers found that the more the subjects used the software, the more significant the improvement was.

"This article is interesting, but it has several weaknesses," says Prof. Moshe Bar, a neuroscientist at Bar-Ilan University. "The researchers offered all subjects a wide range of interventions, so it is difficult for us to know what helped. Secondly, the fact that they also built the testing tools themselves is a bit unusual in the world of science. And the most important reservation is that there is no control group, and although the difference between those who used the product and those who used less was presented, this effect can also be influenced by motivation."

The real big prize has not yet been found

And yet, he says, the article did show the very possibility of cognitive improvement through external intervention, in a direction opposite to the time passing, and this result is consistent with other existing studies.

"Research today has reached two main conclusions. One is that if we train a certain ability, with high probability we will be able to strengthen it. If, say, someone has a challenge in recognizing faces, he will be able to train specifically on face recognition and improve in it. If people do Sudoku, they will improve in Sudoku."

But many older people do Sudoku not to win a Sudoku competition one day, but to "keep the brain."

"The problem is that until today it has not been unequivocally proven that if we improve a certain ability we will be able to improve other abilities as well. This question is called the transferability question, the transfer of the gain you achieved, its generalization. We do not have enough hours in the day to train on all abilities, and if we find one training or one intervention that improves brain function across the board, this is the big prize in this field."

The key is actually outside the brain

Studies from recent years are trying to break this barrier. For example, an article published in 2023 in the journal BMC Psychiatry showed that training in tasks of executive functions and working memory managed to improve scores in other areas as well in subjects with mild cognitive decline.

"In fact, when asking what can improve all abilities together, for now the answer is not training in cognitive tasks, but physical activity, especially aerobic, which actually grows new neurons and maintains existing ones. Sleep is also very important."

A review article published in 2024 in the journal Nature Reviews, led by Prof. Eric A. Smith from the University of Calgary in Canada, supports this assumption, that brain health does not necessarily need to be sought in the brain. The article showed that heart health, endocrine health, gut bacteria mix, and kidney and lung health affect brain health no less than biological processes that we already know how to identify in the brain.

Most importantly, let the brain enjoy

A paper published in 2025 in the journal NPJ Aging found that cognitive training changes brain scans in a way that is identified with cognitive improvement. Prof. Yaniv Assaf, from the School of Neurobiology at Tel Aviv University, notes that the reason we have not yet seen the results of these tools is the weakness of the measures.

"I believe that the trend of lowering the cost of brain scans, among other things with the help of artificial intelligence, will greatly advance research in this field. But I have one recommendation regarding any type of training - you need to enjoy. When the brain enjoys, it releases dopamine that signals that this behavior is rewarding. If you don't enjoy, nothing will come of it."