Yet doing 'brain exercises' such as these can make us all up to 40 per cent cleverer within seven days, according to research by a BBC programme this week.

The tests conducted for Get Smarter in a Week appear to bear out the growing belief among scientists that making simple changes to our lifestyle can lead to significant improvements in how well our brains function.

The programme found that a combination of techniques based on healthy eating, physical activity, sound sleep and stimulating your mind through solving puzzles and remembering lists makes people sharper, more confident and better at making decisions.

The usefulness of such methods will be tested on 100 volunteers from around the UK in an experiment that will get two hours of prime time television on BBC1 on Saturday night. 'IQ has traditionally been thought of as a fixed measure of someone's intelligence,' said Philip Morrow, the show's executive producer.

'But an increasing body of scientific opinion holds that you can take steps in your life to actually improve your brainpower by, for example, enhancing your memory, working on your spatial awareness, doing things differently to normal and eating healthily. Scientists say you will see noticeable improvements within a week. Our show is seeing if the science works.'

When the production team did trial runs among 15 volunteers, who each followed a 'get smarter' regime for a week, they expected their guinea pigs would be about 10 per cent cleverer at the end of it. What they found was that some performed up to 40 per cent better than in the initial assessment. However, one man who had gone out on a stag night the evening before the second test found his score 20 per cent down - proving that alcohol damages mental function.

The 100 contestants on Saturday's show spent last week following as much of the advice in a 50-page Get Smarter Guide as they could manage. Its recommendations include moving around your home blindfolded, using your computer mouse with your 'wrong' hand for an hour a day, and playing games such as Scrabble and charades.

The results will be unveiled when the programme airs. But early indications are that the volunteers had benefited from taking part. 'Some of them were ringing up and saying that this had totally transformed their lives or that they had had their first good night's sleep in five years,' said Morrow.

'A lot of people feel they are under-performing in their life, that they are letting themselves down, in terms of their ability to handle events or thinking that people at work are cleverer than them. This programme shows everyone can get smarter, and feel better, if they do these things.'

· Get Smarter in a Week, Saturday, BBC1 at 6.35pm and 9pm

THE GET SMARTER GUIDE

Saturday

Brush your teeth with your 'wrong' hand and take a shower with your eyes closed.

Sunday

Do the crossword or Sudoku puzzle in your Sunday paper and take a brisk walk.

Monday

Have oily fish for dinner, and either cycle, walk or take the bus into work.

Tuesday

Select unfamiliar words from the dictionary and work them into conversations.

Wednesday

Go to yoga, Pilates or a meditation class, and talk to someone you don't know.

Thursday

Take a different route to work; watch Countdown or Brainteaser.

Friday

Avoid caffeine or alcohol; memorise your shopping list.