If you're like me, you know this feeling.

Maybe you're at a party or you're walking down the street and suddenly out of a sea of

passing faces, one of them lights up looking right at you.

This person starts waving, says hello.

This person is glad to see you and you, you have no idea who you're looking at.

This is Hidden Brain.

I'm Shankar Vidhantham.

Today on the show, we're talking about faces.

Recognizing faces is a crucial skill.

It's so crucial that there are regions of the brain devoted to facial recognition.

But although your mind is amazing at identifying your boyfriend or your child in a crowd,

there are important limits to this ability.

Some of us, like me, are extremely bad at it.

Some of us are terrific.

On today's show, we look at some people who are on opposite ends of the spectrum and

talk about how our ability to recognize faces has broad implications in our lives.

We'll start with someone whose job requires her to be quick with faces.

She's a cop.

My name's Alison Young and I'm a police officer in the Metropolitan Police in London.

She started out several years ago working on response teams in East London.

These are the cops who mostly just respond to 911 calls.

Then, about three and a half years into that job, she and a bunch of her fellow officers

...