In graduate school at the University of Wisconsin-Madison, I proctored law school exams to earn extra money. At the end of one exam, while I was collecting the final papers, I overheard two students discussing their answers on an essay question about sentencing. One said to the other: “I gave the rich guy a lesser sentence because I figured, since he had such a cushy life, it would take less punishment to get through to him.” There’s your next crop of lawyers, I thought, doling out the prison sentences to the poor and letting the rich off with a slap on the wrist.

Well, it turns out that there is a well-documented psychological phenomenon behind what I’d overheard. Morten B. sent along an essay by Jason Silverstein in which he reviews the literature on the racial empathy gap. All things being equal, if you show a person an image of a dark- and a light-skinned person being harmed, they will most likely react more strongly to the latter. Studies have found evidence of this using both self-report and measures of brain activity. Notably, both black and white people respond similarly.

Here are the results of six studies using self-report; in the first four, the relationship between race and how much pain subjects attributed to the target was statistically significant:

What’s going on?

Silverstein explains that this isn’t necessarily about racial animosity or even identification with one’s own group (remember that both black and white people show this response). Instead, it appears to be related to the perception that black people have already had to cope with a great deal of pain—from racism, poverty, poor health, etc—and, as a result, have a greater pain threshold. In other words, they are less sensitive to pain because they’ve been hardened.

Efforts to parse out whether this effect is due to race specifically or perceptions of whether a person has lived a hard life suggest that it might be primarily the latter. But, as Silverstein points out, we tend to homogenize the black population and assume that all black people face adversity. So, whether the phenomenon is caused by race or status gets pretty muddy pretty fast.

In any case, this is perfectly in line with the soon-t0-be-lawyer I overheard at Wisconsin. He gave the “hardened criminal” a harsher sentence than the person convicted of a white-collar crime because he believed that a greater degree of suffering was required to make an impact. That was just a hypothetical case, but Silverstein reviews research that shows that the racial empathy gap has real world consequences: undertreatment of pain (even in children) and, yes, harsher sentences for African Americans convicted of crimes.

This post originally appeared on Sociological Images, a Pacific Standard partner site.