Andrew here from BBC Learning English.

Just so you know, this programme is from the BBC Learning English Archive and was first broadcast in November 2006 on our website.

And now, on with the show.

Hello.

I'm Callum Robertson and this is Entertainment Today.

We're talking about love.

Love is one of the strongest emotions there is and that's how usually we think of it, as an emotion.

Love is the topic of many songs, poems, plays, films, paintings, greetings cards and t-shirts.

And as a famous song says, love is all around us.

But is there more to love than emotion?

Have you ever wondered why we are attracted to some people and not to others?

Here's psychologist Dr Glenn Wilson.

What does he think?

Is there a science to love?

There certainly is.

There are some rules in the sense of scientific rules and what is the similarity principle that other things being equal, we like people who are rather similar to ourselves.

Yes, he does think there are some scientific rules to love and attraction.

What is one of the rules he mentions?

Listen again.

There are some rules in the sense of scientific rules and what is the similarity principle that other things being equal, we like people who are rather similar to ourselves.

Dr Wilson talks of the similarity principle, the idea that we like people who are similar to ourselves.

He goes on to explain more.

What particular feature does he say we look for similarity in?

Generally speaking, we choose the eye colour that is similar to ourselves but we would also go for an eye colour that matches our opposite-sex parent more than our same-sex parent, as though we are using the opposite-sex parent as a kind of a blueprint for what it is that will attract us.

So apparently eye colour is important too.

We choose people with similar eye colours or even people whose eyes are similar to those of our opposite-sex parents.

So in other words, for a woman, that's eyes which are similar to her father's and for a man, similar to his mother's.

That's one of the subconscious rules of attraction.

Subconscious.

It's not something we think about when we see someone.

We don't think, aha, she's got eyes like mine.

I think I love her. bbclearningenglish.com So what are some of the other subconscious rules of attraction?

Here's Dr Glenn Wilson again with Chris Evans from BBC Radio.

What is the principle that he mentions?

There are some principles.

Symmetry, for example, that is having one of everything down the middle and two of everything down the side is very important.

And if the two sides match each other perfectly, if the mirror images would fold over on top perfectly, then that person is more likely to be attractive because it implies a healthy development.

In that part of the interview, he mentioned the principle of symmetry.

If the left hand and the right hand side of the face are symmetrical, if they are like a mirror image, then that makes that person more attractive.

But why is that?

Listen again.

That person is more likely to be attractive because it implies a healthy development.

Having symmetrical features implies a healthy development.

And this is one of those subconscious things which makes us find people attractive.

And finding someone who looks healthy is important because subconsciously, we are looking for a partner who can produce strong and healthy offspring.

Offspring is another word for children and as with animals in the wild, our instincts are to mate, to mate, to produce offspring.

Something that is often said is that opposites attract.

It's certainly true for magnets, but what about people?

In the next section from the interview with Dr Wilson, he talks about pheromones and the immune system.

Pheromones are chemicals which humans and animals produce.

These chemicals can't be smelt, but they are detected by others and can affect the way they behave.

And the immune system is part of the body's natural defences.

It's the system that fights off diseases in the body.

So Dr Wilson, is there any truth to the belief that opposites attract?

There's not much truth in it, beyond the idea of the gender opposite.

But there's another interesting finding, which is that we seem to be able to detect by smell or pheromone, a person who has a different immune system from ourselves, such that when we mate with them, our offspring will be given a broadened immune spectrum.

Well, Dr Wilson says there's not much truth in the saying that opposites attract, except in the basic idea of being attracted to someone from the opposite sex, although that's not true for everybody.

However, he does say that through the action of pheromones or smells, we are able to detect people who have a different immune system.

This will be good for any offspring because it means they will have the benefit of two different immune systems and should grow up stronger and more able to fight disease.

So there we have it.

Love is a powerful emotion, but there is a lot of science behind it, and a lot of the attraction we might feel for someone is based on things happening in our subconscious.

Now, that's what I call romance!