I'm a reader in cognitive psychology and the University of Huddersfield.

I've always had an interest in how people deceive others -

for example, if I were lying to you right now, how would you know?

Would you look at my eyes? At my body language?

Would you look me up online?

I'm Chris Street,

I'm a reader in psychology at the University of Huddersfield.

If we want to detect deception we need to stop looking for

those visual behaviours that we think relate to deception,

like eyecontact or fidgeting.

Instead we need to start thinking about

the pieces of information we can find in the world

that match or mismatch with the statement being offered.

If you want to be able to accurately detect

somebody's lies or truths

what you need to do is, you need to listen to what they're saying

and the way that they say it, not how they're acting.

Think about when you are talking to somebody,

you meet them for the first time, now any good poker player will tell you

that it is very easy to control your face.

Therefore facial cues really aren't good cues

of whether or not somebody is lying or telling the truth.

What you should be doing is

you should be listening to what people say -

the verbal cues and the way in which they say it -

the vocal cues.

A lie teller, because they are trying to think very hard,

they will use probably the same word over and over again

over a very short period of time.

There's some general research that suggests

we are about 54% accurate when it comes to detecting lies and truths

and as I always say, "If that's the case, you might as well flip a coin -

you'll be just as accurate."

There are some people who think they are lie detection wizards.

That they can read subtle clues that we give off.

The research suggests that this isn't the case,

that there aren't lie detection experts.

Liars just don't give themselves away in any obvious fashion.

There aren't good clues to deception, we don't avoid eye contact,

we don't scratch our face when we're lying or telling the truth.

These just aren't reliable indicators and so, expert or not,

we have no good information on which to make that decision.

We have this idea that if somebody is lying to us

they can't keep our eye contact.

Now of course, liars know this

and what they will do is they will keep your eye contact

ever so slightly longer than normal,

just enough to make you feel uncomfortable.

Number two misconception tends to be

when people lie they move about a lot,

they kind of get very nervous.

In fact the opposite is true. When we lie, we have to think really hard.

So imagine you've got a limited amount of energy,

you will channel all of that energy into telling a lie

and as a consequence, you will become ever so slightly stiller

than you normally are.

A third misconception is the idea that

if we look up to the right or we look up to the left,

it determines the type of lie or truth that we're telling.

A recent piece of research has in fact debunked the idea

that looking up that way or looking up that way

is a good way to detect deception, it's not.

My top tip for accurately determining

whether somebody is lying or telling the truth

is using something that we call the honest baseline

Now the honest baseline is understanding

how people act and speak

when they're not stressed and when they're being truthful.

So when we ask them a question, now if we find a pretty even match

between the way they normally act and the way that they're acting now,

we will be fairly happy that they're probably telling us a truth.

If we find a mismatch,

it might indicate that there is something going on here

that we need to follow up with in a bit more detail.

ALIED theory, or the...

...argues that when we try to decide

if someone's lying or telling the truth

what we're doing is actually quite functional

and informed with our past experience

and with the information available in the world.

For instance if I claim to have gone to France last week

and I have a selfie of me in France

that's a great piece of information that I was actually there.

But often we don't have that sort of information, so what do we do?

ALIED theory claims that we, rather than simply guess,

rely on our past experience of the world to make an informed judgement.

People tend to be truth biased,

they tend to believe people are telling the truth,

and that may be something we want to get rid of.

The best thing to do is just try to keep an open mind

and engage with the situation in a sceptical manner.

I'm Dr Chris Street. I... Nope.

Do I have to say it exactly how you've done it

or can I just say it as it comes out?

I'm Dr Chris Street.

I'm a reader in cognitive psychology at the University of Huddersfield.

I'm like, moving my hands here, you can't see.

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