It's long been said doing a daily crossword or Sudoku puzzle is key to keeping the brain active.
But whether exercising the white stuff can stave off dementia is more hotly contested.
Now scientists have discovered that the type of brain training programme we do is key to reducing the risks of the degenerative brain disease.
Just 11 sessions of a specific technique called speed processing could help to cut the chances of older patients developing the disease - by almost half.
And each exercise - aimed to improve the time and accuracy of someone's mental ability - could slash the risk by 8 per cent every time.
Older patients could cut the risk of developing dementia by 48 per cent by having just 11 sessions of a specific brain training technique called speed processing
And those who completed the speed processing training experienced levels of improved attention, experts found.
They also had reduced symptoms of depression, a better functional performance and improved driving ability.
But memory and reasoning training had no benefit on preventing dementia, experts found.
Lead researcher Dr Jerri Edwards, claimed some brain training does work, but not all of it.
She said: 'The mistake some people make is thinking that all brain training is the same.
'Lumping all brain training together is like trying to determine the effectiveness of antibiotics by looking at the universe of all pills, and including sugar pills and dietary supplements in that analysis.'
Healthy older adults also had reduced symptoms of depression, a better functional performance and improved driving ability
Researchers looked at over 50 studies which focused on speed processing training.
They also used findings from their ACTIVE study, which examined the effects of cognitive training programs on 2,832 healthy older adults aged between 65 and 94.
Participants were divided into three groups. One got training for memory improvement, one for reasoning and one with computerized training in speed-of-processing.
In the speed training, which emphasized visual perception, individuals were asked to identify objects on a screen quickly. The program got harder with each correct answer.
Participants had 10 one-hour training sessions conducted in a classroom setting over five weeks. Some received four additional 'booster' sessions one year after the original training, and four more two years after that.
Despite speed processing training proven to have benefits, memory and reasoning exercises had no effect on preventing dementia
Scientists measured cognitive and functional changes immediately and at one, two, three, five and 10 years after the training to see if it affected how participants performed daily tasks.
Dr Edwards pointed to the speed of processing research around driving as a concrete example of how this training generalizes to everyday activities.
Studies have shown speed of processing training resulted in improvement in reaction time.
The exercises helped participants gain an extra 22 feet of stopping distance at 55 mph and a 36 per cent decrease in dangerous maneuvers.
In addition, 40 per cent fewer people stopped driving altogether and there was a 48 percent reduction in at-fault crashes, she said.