The eyebrow flash. When we first see someone we're attracted to, our eyebrows rise and fall. If they are similarly attracted, they raise their eyebrows in return. Never noticed? It's not surprising since the whole thing lasts only about a fifth of a second!

We're not consciously aware of doing it, but it's a gesture that is duplicated by every culture on Earth. In fact, some experts claim it's the most instantly recognised non-verbal sign of greeting used by humans.

The trick is to watch for it when you meet someone you fancy. Better still, tell them you're interested on a subconscious level by prolonging your eyebrow flash for up to one second - deliberately raise them while catching their eye for full impact.

Blinking. If someone likes what they see, their pupil size increases and so does their blink rate. If you want to up the odds in your favour, try increasing the blink rate of the person you're talking to, by blinking more yourself. If the person likes you, they'll unconsciously try to match your blink rate to keep in sync with you, which in turn, makes you both feel more attracted to each other!