A daily regime of mental gymnastics can improve people’s intelligence and make them better at their jobs, a study has shown.

Volunteers who took part in tests found that they had better memories, were able to reason more effectively and could solve tougher problems.

Devoting 25 minutes a day to specially designed mental exercises is enough to bring about significant improvements, but even five minutes should be enough to help.

Su doku, The Times crossword and other tests provide valuable mental exercise for the brain but have limited value because they help mental improvement only at similar tasks.

The new study, however, stimulated problem-solving abilities in the brain that can be applied to a variety of circumstances. The improvements were observed after subjects were put through rigorous exercises designed to tax their mental agility.

So marked was the change in individual ability among the volunteers that researchers were confident they would perform better at work.

Dr Martin Buschkuehl, of the University of Michigan in the United States, said: “The longer you put into it, the bigger the improvement that will be made.”

The US study contradicted previous research projects which had concluded that mental exercises had little bearing on improved memory and intelligence. The difference with the latest study is that the mental exercises were specifically designed to continually challenge the people taking them.

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