Cast your eye around any commuter train and you will almost certainly see more than one person engaged in a sudoku puzzle, crossword or similar test of mental acuity.
Some may even have shelled out for a subscription to play brain training games – apps and websites that offer simple tests of cognition professing to boost intelligence or ward off the onset of dementia.
But the scientific evidence for the efficacy of brain training remains highly contested.
In 2014, 70 leading neuroscientists and cognitive psychologists signed a letter stating that existing studies offer insufficient evidence to show the games “improve general cognitive performance in everyday life, or prevent cognitive slowing and brain disease”.
A comprehensive review of the scientific literature by seven psychologists last year also found flaws in all the studies backing positive claims for brain training.
The one thing scientists do seem to agree on is that regularly playing brain training games increases people’s aptitude for those specific mental tasks, or very similar ones.
So if your only goal is the endorphin rush of in-game achievements, you may be in luck, but that might not be a good enough reason to pay for a subscription.
Indeed, if your hope is to improve your intelligence or mental skills for the benefit of your home or working life, you may be better off practising the actual tasks you want to get better at.