• Nicole Kidman has advertised the games for Nintendo. Picture: PA
Computer-based mental exercises have become hugely popular in recent years, with many believing they can improve brain function and reduce dementia.
But new research suggests that the games do not actually improve general mental ability.
Brain training has received attention through games such as Dr Kawashima's Brain Training on the Nintendo DS console.
The new study involved more than 11,400 people who were given different types of brain training games developed by researchers to practise.
When their mental skills were re-tested after six weeks, the researchers concluded there was "no evidence" that the games could improve mental ability.
Although practice improved game performance, the skills learned did not transfer to unrehearsed mental tasks, according to the team from the Medical Research Council (MRC).
Players did no better at a series of independent mental tests than another group of volunteers given general knowledge quizzes instead of brain training.
Dr Adrian Owen, from the MRC Cognition and Brain Sciences Unit in Cambridge, said: "Brain training is a multi-million-pound industry, yet up until now there's been a lack of robust evidence to show it really works.
"Our findings will no doubt surprise millions of people worldwide who do some form of brain training every day in the belief that 'exercising' their brain makes them better at everyday thinking tasks.
"In one of our computer games that tests memory by assessing how many numbers could be remembered by players, we found it would take almost four years of playing brain training games regularly each week to remember just one extra digit."
The study was carried out in collaboration with the BBC science programme Bang Goes the Theory.
Viewers aged 18 to 60 took part in the six-week study via the BBC science website Lab UK.
Volunteers were split randomly into three groups, two of which practised six training games for at least ten minutes a day, three times a week. The third control group answered general knowledge questions on the website.
It has also been suggested that such games might help prevent age-related mental decline.
Professor Clive Ballard, director of research at the Alzheimer's Society, said: "This evidence could change the way we look at brain training games and shows staying active by taking a walk, for example, is a better use of our time."
A statement issued by Nintendo to the BBC and included in the programme reads:
"Nintendo does not make any claims that Brain Training or More Brain Training are scientifically proven to improve cognitive function. Nintendo do not have any available spokespeople for interview."
The study was published in the journal Nature.