Arizona State University neuroscientist Michael Varnum has studied this idea quite a bit. For a 2015 study published in the journal Culture and Brain, he and his team asked 58 participants questions designed to determine their social class, including those about their parents' education, their income, and their perception of their own social status. They also asked participants to fill out a questionnaire that measured how empathetic they believed themselves to be. Then, participants each donned an EEG cap designed to measure their brain waves and looked at a series of pained and neutral faces.

Although those of higher socioeconomic status rated themselves as more empathetic — a finding that inspired Varnum to author a whole new study on the phenomenon — the EEG didn't lie. It showed that the higher the subject's status, the less their brain reacted to the pained expressions. According to the study, "these findings suggest that empathy, at least some early component of it, is reduced among those who are higher in status."

Varnum published another study in 2016 that honed in on socioeconomic differences with mirror neurons, the neurons that seem to simulate the actions of others. It found something similar: those of lower socioeconomic status have more activity in their mirror neurons when watching people perform a task. Yet another study out of New York University found that when walking around a city block, higher-class people have a shorter "social gaze" — that is, the amount of time they look at the people around them.

Why would the well-to-do have less empathy for others than the poor? According to The Science Of Us, "It may be that growing up poorer means that you have to rely on others more; it may also mean that you live in a less-secure environment, so you need to attend to others to keep yourself safe."

In the same way, money affords a certain amount of privacy and independence. Those without it spend more time riding on public transit, standing in line for necessities, and doing other things that put them in the presence of other people. A life spent around others requires good skills in social interaction.

On the flipside, Steve Siebold, a self-made millionaire and the author of "How Rich People Think", considers this lack of external focus a virtue. "The rich go out there and try to make themselves happy. They don't try to pretend to save the world," he told Business Insider. "If you're not taking care of you, you're not in a position to help anyone else. You can't give what you don't have."

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