I'm Shankar Vedantam and this is Hidden Brain.

One of the great things about science is that it can change the way we see the world.

Today we have an episode from March 2017 that I still think about all the time.

It's a story that will change the way you think about many things.

Poverty, loneliness, time, even hunger.

It's a tale about the psychological phenomenon of scarcity.

It affects nearly everything in our lives and connects people who appear to have nothing in common.

The story of scarcity is a story of how not having enough of what you need can become the only thing that matters to you.

That I think is the basic scarcity instinct.

We're hungry and then this thing starts going off in the head saying,

do you realize we're hungry? Have I mentioned we're hungry? We're hungry.

The scarcity trap this week on Hidden Brain.

My name is Brandy Drew. I'm from Detroit, Michigan.

Brandy Drew has a story that may sound familiar to you. A story of poverty and debt.

It's the kind of story that may lead people to quick conclusions, so pay attention to your own.

Brandy is now 37. Six years ago, her life unravelled.

At the time, she ran the dining services department at a senior living facility.

She'd been with a company that ran it for more than a decade.

One day, she made a mistake.

I was just in a rush to get home, that was all. Because daycare closes at six.

I get off at five. It was like maybe a 10 mile drive busy traffic area.

And I knew I had to pick up diapers and the easiest thing for me,

...