When I was about 12 years old, one of my friends told me a joke. He asked, “What’s the difference between a bumblebee and a corvette?” When I shrugged he said, “The prick is on the outside of the bumblebee.” Jealousy might be the root of such tasteless jokes–and that makes sense. At some point in our lives, we’ve all craved something we can’t afford. Perhaps we were jealous when we saw somebody else enjoying what we wanted.

But how do we really feel about the rich… and the poor? Psychology researchers Lasana Harris and Susan Fiske wanted to find out. They conducted brain scans at Princeton University in 2006. They showed the subjects photographs of people representing various levels of wealth. In the pictures, some were enjoying the fruits of their riches. Others were destitute.

When we see images of other people, it usually activates our brain’s prefrontal cortex. But when we see images of inanimate objects (like rocks or dirt) our prefrontal cortexes don’t engage.

When our prefrontal cortex lights up, our brains connect with the picture. It seems to say, “I’m a human being. This is a human being. We have a connection.” But when the research subjects saw images of people in extreme poverty, the prefrontal cortex didn’t engage. It lay dormant, much as it would if the subjects saw a rock, a grasshopper or a pile of dirt.

This might say a lot about humanity’s darkest side. Many of us have wondered, for example, how genocide could take place. Such widespread murder is often the brainchild of a single, evil mastermind. But these creeps don’t single-handedly pull rifle triggers or stuff people into gas chambers. They convince hundreds or thousands of others to commit horrible deeds.

For example, in the 1970s, a man known as Pol Pot killed a quarter of Cambodia’s population. He dreamed of returning Cambodia to its glorious past, when its Angkor temples and culture thrived on a rice-based economy. Educated Cambodians, he figured, would be a threat to his backward plan. That’s why he had them killed. He also killed their children. If somebody wore glasses, they were murdered too. Glasses were seen as a sign of intellect.

People often wonder how he convinced so many others (mostly teenagers) to commit mass murder. But, like the Jews that were forced into concentration camps during World War II, they looked rough when they arrived. Starved, hungry and dirty, they grew less “human” in the eyes of their captors.

Harris and Fiske’s study revealed something similar. Some of subjects might have argued with the results. They might have said, “No, that brain scan doesn’t reveal how I really think.” That might be true. But such scan results give us something to think about.

The Center for Poverty Research at the University of California says U.S. poverty rates have fluctuated within a narrow band since 1964. Most years, poverty rates ranged between 11 to 15 percent of the U.S. population. The U.S. Consensus Bureau measures the poverty line based on the number of people in a household. For example, a household with a mother, a father, two children and one great-aunt would be considered poor if the household income were below $29,360.

They would be considered extremely poor if their income were half that level ($14,680 a year or less). Unfortunately, the percentage of extremely poor people in the United States is growing. It represented about 3.8 percent of households in 1975. In 1985, it represented about 5 percent of households. By 2016, more than 6 percent of America’s households were considered extremely poor.

It’s important to reflect on how we treat the poor. A couple of years ago, I wrote about a woman named Joon Madriga. She used to be homeless, and she wrote a book to help others escape poverty. I asked what she disliked most about living on the streets. She said other people treated her as if she were invisible.

This brings me back to those MRI scans. We might feel a tinge of envy when we see someone rich. But there’s a proverb to remember when we see the destitute:

There but for the grace of God, go I.

Andrew Hallam is a Digital Nomad. He’s the author of the bestseller, Millionaire Teacher and Millionaire Expat: How To Build Wealth Living Overseas