It is often said that old dogs cannot learn new tricks. But even very old people can keep up with people in their twenties, if they just practise enough. Pensioners can struggle to multi-task, whether picking up the telephone and writing down a message, or remembering a shopping list, because older brains process information more slowly. But in a brain-training game which uses multi-tasking, they did just as well as younger people after practising. The research, published in the journal Proceedings of the National Academy of Sciences, tracked almost 200,000 people on the brain-training game.

Are brain-training games any better at improving your ability to think, remember and focus than regular computer games? Possibly not, if the latest study is anything to go by. Joseph Kable at the University of Pennsylvania and his colleagues have tested the popular Luminosity brain-training program from Lumos Labs in San Francisco, California, against other computer games and found no evidence that it is any better at improving your thinking skills. Brain-training is a booming market. It's based on the premise that our brains change in response to learning challenges.

One product, BrainHQ from Posit Science, promises everything from "2x faster visual processing speed" and "10 years in memory" to "more happy days," "lower medical costs," "reversal of age-related slowing," and "more self-confidence." Another, Cogmed, claims to have improved "attention in many with ADHD," as well as "learning outcomes in reading and math [for] underperforming students." Lumosity by Lumos Labs, perhaps the most pervasively marketed of them all, ran ads that included characters from the Pixar film Inside Out. People are certainly buying the hype--and the games. According to one set of estimates, consumers spent 715 million on these games in 2013, and are set to spend 3.38 billion by 2015.