For 25 days, protesters around the world have marched to demand racial justice, sparked by the death of George Floyd at the hands of police. Anti-black violence is not new, nor are protests against it, but this time the movement caught fire.

Drastic changes, such as dismantling police departments, are gaining steam in Minneapolis and beyond. In two weeks, support for Black Lives Matter among U.S. voters increased as much as in the previous two years. And in a recent Washington Post-Schar School poll, 69 percent reported that Floyd’s death represented broader problems in police treatment of black Americans.

Countless people who sat on the sidelines of this struggle have now joined in. We can ask, as many have, why now? But we might also ask, why not earlier? What kept people — especially those with relative privilege — from supporting previous movements, such as the protests in Ferguson, Mo., following the death of Michael Brown?

One key to this comes from research on the perverse relationship between power and empathy. We often think of empathy — people’s ability to share and understand each other’s experiences — as a hard-wired trait, but it’s actually more like a skill. The right experiences, habits and practices can increase our empathic capacity, the same way we can get stronger by going to the gym. There’s a dark side to this idea: Other experiences can cause our empathy to atrophy, like a muscle we don’t use.

Power and privilege, in particular, sap our ability to understand others. In one series of studies, the psychologist Michael Kraus and his colleagues measured people’s socio-economic status, as well as their ability to decipher emotions in pictures and in-person interactions. People higher in status were less accurate about other people’s feelings. More recent work has replicated these results and also found that high-status individuals make more errors when trying to take other people’s perspective.

Kraus and his colleagues have documented other empathic failures that come with privilege. Higher-status individuals display less interest when talking with strangers, and report less concern for the suffering of others. These gaps play out in racial contexts as well. In another study, Kraus found that high-income white Americans overestimate racial economic equality more than black Americans or low-income white Americans.

These findings were bleak enough to make one journalist conclude, “power causes brain damage.” But powerful people are not incapable of empathy and should not be let off the hook from working at it. Like other skills, empathy takes practice, and people practice it when they are motivated to do so. Individuals who are relatively underprivileged realize they need others to succeed, whereas people with power often decide they can go it alone. Consistent with this idea, lower-status individuals pay more attention to faces, people and social cues than those with high status.

People without power often have to understand the perspective of high-power groups, which is the default in media, culture and work. As the comedian Sarah Silverman once put it, “Women are so keenly aware of the male experience because our entire existence had to be kind of through that lens.”

By contrast, high-status individuals don’t have to understand others’ perspective to survive. This is one way privilege works its way into our minds. Not only are privileged people exempt from material struggles, they can comfortably ignore everyone else’s.

In some cases, powerful individuals have incentives not to understand. Genuinely peering into others’ worlds might force them into ugly realizations that they contribute to and benefit from injustice. To avoid that discomfort, they might turn down their empathy even further. In one troubling series of studies, psychologists reminded members of high-power groups — such as white Americans — of their group’s responsibility for past violence — for instance, against Native Americans. Participants responded by dehumanizing victims to avoid guilt.

This is one irony of power: It expands the change a person could make while narrowing the aperture of who they truly see. But this is not inevitable. When powerful people choose to empathize, they become more cooperative and more invested in justice. In one particularly relevant series of studies, Emile Bruneau and his colleagues asked members of low-power groups to “perspective give,” sharing their stories, and high-power individuals to perspective take, paraphrasing what they’d heard. These dialogues increased connection and positive regard between groups — not by ignoring existing power structures, but by reversing them.

In the past few weeks, many people have opened their eyes to suffering they had previously ignored. Much credit for this should go to the activists and organizers who have made it harder to look away. Can an increase in concern about racial injustice last? Empathy is a powerful psychological spark, but it often extinguishes quickly to support long-term change. As emotional stories leave our collective consciousness, people move on. Suffering continues, but those in power no longer see it.

Rather than depending on empathy to last, another strategy would be to leverage the intense care and energy of this moment into structural change — for instance, commitments to diversify leadership in education, business and government. Rather than depending on people in power to listen more intently, change might come when we ensure that people who have previously been kept out of power have more chances to speak and be heard.

Jamil Zaki is a professor of psychology at Stanford University and author of “The War for Kindness: Building Empathy in a Fractured World.”