Some people say they can tell by a person's eyes. Others watch for tell-tale signs like blushing or nose-touching. Most of us just haven't a clue. Which is worrying, because apparently the average person tells lies 40 times a day - honest! Or so they say (how would they know, anyway?).

No doubt some of us are better at spotting a liar than others, but are there any sure-fire ways to catch them out? Probably not. It seems that with some people - think journalists, estate agents etc - it's just best to assume they're being economical with the truth. If the pad really is that great it would surely cost a lot more, wouldn't it?

So how do you spot a liar?

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  Do you have a special technique to catch people out?

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  Is lying a human survival instinct?

• Do you pride yourself on being a good liar?

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  Why do some people seem compelled to lie unnecessarily?

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  Who are the worst liars in history? Do you know any of them?

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  Do all liars get found out in the end? (Personally, I doubt it.)

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  Is it now more socially acceptable to lie than it was in the past?

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  Which kinds of people are usually the most trustworthy?

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  Has anyone lived and never lied, or is that impossible?

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  What's the oldest trick in the book?