成人快手

All week our science man Michael Mosley has been looking at ways of keeping yourself looking fit and young.

In the fourth film of the series, he looked at how it seems to be possible to turn back the clock of our ageing brains, and regain some of our lost brain power through problem solving.

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Test your reactions

Click here to play the Sheep Dash game!

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After playing, remember to click the back button on your web browser and tell us how you got on, below. Add your score.

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How to play: You have to fire a tranquiliser dart and stop five sheep dashing for freedom. It's easy to play - you only have to click your mouse button five times - and each game lasts under a minute. At the end of the game it tells you how long it took you to react to the dashing sheep.

And tells you if you're a sluggish snail, ambling armadillo, bobbing bobcat, rocketing rabbit, or turbo-charged cheetah.

Which one are you? After playing, remember to click the back button on your web browser and tell us how you got on, below. Add your score.