Two organs, otherwise used for eating and speaking, are rubbed and pressed against one another with increasing force.

Accompanied by the secretion of saliva.

A tongue normally precisely manipulated to articulate vowel sounds.

Or to push mash potato or broccoli to the rear of the palate.

Now moves forward to meet its counterpart, whose tip might touch in repeated staccato movements.

One would have to carefully explain to an alien visitor from Keppler 9B what's going on.

They're not about to bite chunks out of each other cheeks or attempting to inflate one another.

Why is kissing so significant and potentially so exciting?

Sexual excitement is psychological.

It's not so much what our bodies happen to be doing, that's getting us turned on.

It's what happening in our imaginations that matters.

Partly, the excitement of kissing is the result of social codes being breached.

We could imagine a society where it was very forbidden, and yet very special for two people to rub the gap between index finger and thumb together.

The first time you did it, would be something you'd remember all your life.

The huge meaning of kissing is something we've built up by social agreement.

And its fundamental definition is: I accept you, enough to do something potentially quite revolting with you.

The inside of a mouth is deeply private, ordinarily it would be utterly nauseating to have a stranger poke their tongue into your face.

To allow someone to do these things, signals of a fundamental level of acceptance.

All of us suffer from strong feelings of shame.

Which another's kiss starts to work on overcoming.

Aside from our public identities, we all have lonelier, private selves.

Which is what we feel we getting and giving access to...through a kiss.

Our mouths become privileged arenas in which to surrender our defenses.

And gift ourselves to another, physical pleasure aside.

That's why it's so very exciting.