From this article a while ago that ran on The Guardian:
“The multimillion dollar brain training industry is under attack. In October 2014, a group of over 100 eminent neuroscientists and psychologists wrote an open letter warning that “claims promoting brain games are frequently exaggerated and at times misleading”. Earlier this year, industry giant Lumosity was fined $2m, and ordered to refund thousands of customers who were duped by false claims that the company’s products improve general mental abilities and slow the progression of age-related decline in mental abilities. And a recent review examining studies purporting to show the benefits of such products found “little evidence … that training improves improves everyday cognitive performance”.“