The idea that crosswords and puzzles like Sudoku and the world-famous Wordle are a kind of exercise for the brain has long been embedded in our consciousness. But the benefits of these activities are increasingly discussed in medical language.
The brain is like a muscle, and if it is not consciously exercised, it is destroyed, many argue. Over the past two decades of brain imaging, as volunteers learned new skills such as juggling, snapshots taken every few weeks revealed natural changes in its structure, providing new evidence of our ability to rewire our brains at will. While you care for this information dementia growing, it has inspired the entire software industry to get into brain training. But the scientific evidence that crosswords and puzzles can boost the brain is, as it turns out, complicated.
Crosswords and puzzles are, if anything, positively correlated with cognitive abilities. A recent study of more than 9,000 participants found that lifestyle choices such as playing video games, drinking alcohol, exercising, and learning musical instruments explained about 7-9% of the variance in cognitive scores. Playing board games and puzzles was the strongest predictor of scoring high on reasoning (thinking) tests and the second most important predictor of short-term memory and verbal skills (video games, by the way, were as important a predictor of cognitive abilities as well). However, these findings are treated with great caution.
“It’s possible that people who are better at puzzles in the first place spend more time on them,” says Adrian Owen, a professor at Canada’s Western University who led the study. This is how it turns out they may already be people with good cognitive abilities.
This has not stopped others from arguing for a causal relationship, especially when the same tests are performed in older age groups. A 2021 study based on lifestyle surveys of participants concluded activities such as reading and crossword puzzles can stave off dementia by up to five years. Another study suggested that people who do language/word puzzles “have brain function 10 years younger than their age”.
The benefits are often presented as such because there are no known mechanisms to target the underlying biological causes of dementia, puzzles such as the accumulation of amyloid proteins in Alzheimer’s disease or the loss of blood flow to the brain in vascular dementia. A way to increase “cognitive reserve”. The idea sounds logical: the larger your mental reserve, the longer it takes to deplete it. But while there’s no doubt that doing a crossword puzzle every day will make you a better crossword puzzler, evidence to support broader cognitive benefits—which would be meaningful in everyday life—was not found.
“The analogy of training the brain and exercising the body is often used, but it can be a little misleading,” says Dr. Joe Hardy, who researched the effectiveness of crossword puzzles while working for brain training software company Lumos Labs. “If you train the muscles, you can see physical changes. They are visible and measurable and happen quite quickly. The brain is completely different. It does not show big changes neither in its volume nor in its structure.”
In fact, neuroscientists have found that when we train on single cognitive tasks, we often fail to detect broader benefits. “When you learn to perform a task, you only strengthen the white matter networks involved in that task,” says Owen. “So if you have five nodes for crosswords and five nodes for sudoku, and three overlap, it doesn’t mean crosswords make you better at sudoku.”
To some extent, brain training companies are incorporating these findings into their products. In a study Hardy led while working at Lumos, nearly 5,000 participants spent 15 minutes solving either crossword puzzles or a series of 49 different brain exercises at least five days a week for 10 weeks. Training is presented in the form of mini-games, for example, remembering things in a suitcase, matching tiles based on rules that change from time to time, rescuing lost pets using the most efficient route, deciphering words, as well as math exercises. After the training period, the volunteers completed seven cognitive assessments aimed at measuring short-term memory, processing speed, grammar and numerical reasoning.
On all tests, only marginal cognitive benefits were seen for the crossword group, with the exception of the grammar assessment, where there were greater improvements for those who did the brain training exercises. However, speaking a few years later, Hardy admitted that the study had some weaknesses. First, people were recruited through a cognitive training website, which means they may have had a priori expectations that brain training would have stronger effects on cognition. Similarly, one explanation for the improvement in grammar skills is that the crossword puzzles actually improved those skills, and another is that the volunteers expected to do better and therefore went into the test with more confidence. “The placebo effect is a real problem in a lot of behavioral research,” says Hardy.
According to him, the issue is how to define cognitive ability. And this is something that there is no agreement in the scientific community…