This summer’s Black Lives Matter protests shifted White American attitudes toward race quite significantly. Beginning with the recording of George Floyd’s killing at the hands of Minneapolis police on May 25, the protests quickly shifted attitudes considerably, as TMC editor Michael Tesler noted here on June 9. In late May, 57 percent of Americans said police officers were more likely to use excessive force against Black people than against White people, according to Monmouth University’s June 2 poll, conducted around the peak of the protests — a big jump from just 33 percent in December 2014. Roughly three out of four Americans called “racial and ethnic discrimination” a “big problem” in the United States — up from only about half of Americans in 2015.

And the protests haven’t ended. More recently, protests erupted after a Louisville grand jury declined to charge police officers in the death of Breonna Taylor, an emergency medical worker shot and killed at home during a raid in March.

But will those changes in attitudes last — or fade? Over the past few years, political scientists, economists and psychologists have made important findings suggesting that prejudice has deep roots and can be transmitted from parents to children over many generations. That’s true for anti-Black racism, anti-Semitism and any other form of bias. But they’ve also found that attitudes can shift — and that protests can help those increases in tolerance last.

Prejudice can last for generations

Much of the social science literature on prejudice’s persistence explores anti-Semitism in Europe. Findings suggest that ethnic hatred can flourish in certain places over shockingly long time spans. As the Black Death tore through medieval Europe, Jews were widely blamed for poisoning wells. Pogroms broke out across Europe. In Germany, for example, Christians launched pogroms of varying intensities across the country. Almost six centuries later, as the Nazis rose to power, the same places that burned Jews in the middle of the 14th century showed markedly higher levels of anti-Semitism than neighboring towns. They were six times more likely to attack Jews as the Nazis rose to power. And today, municipalities that supported the Nazis more enthusiastically in 1933 are more likely to support the hard-right Alternative for Deutschland (AfD) party. Far-right party vote share in Germany and Poland are higher in places closer to Nazi concentration camps.

Scholars have found similar results for anti-Black racism in the United States. A 2016 paper found that White people who live in Southern counties that had higher proportions of enslaved people in 1860 are more likely, today, to express racial resentment toward Black people, and identify as Republicans and oppose affirmative action. The culture, norms and institutions of the Southern “Black Belt” — the focal point of antebellum slavery, where, according to the political scientist V.O. Key, Southern whites had “the deepest and most immediate concern about the maintenance of white supremacy” — were transmitted within families and across generations. Passed through institutions, families and communities from one generation to the next, prejudice can last for decades, if not centuries.

Increases in tolerance can persist, too

But just as certain historical events can fuel prejudice that can last for centuries, other events can boost tolerance for generations. Take, for example, the interaction between Black American soldiers and Britons during World War II. At the time, around 10 percent of the American troops stationed in the United Kingdom were African Americans. The U.S. Army was strictly segregated, but many Britons resisted official attempts to treat Black GIs as inferior. As a result, U.S. War Department surveys found that while White GIs grew less sympathetic to English people while stationed there, most Black GIs became more positive about them. The feeling was mutual. As Black soldiers visited local restaurants, bars and dance halls, many Britons saw and interacted with African Americans for the first time — and responded positively. “I don’t mind the Yanks,” one Englishman remarked, “but I don’t care much for the white fellows they’ve brought with them.” Or as George Orwell wrote, “The general consensus of opinion seems to be that the only American soldiers with decent manners are the Negroes.”

According to a new paper by economists David Schindler and Mark Westcott, the effects of these interactions persisted long after most U.S. troops had returned home. Schindler and Westcott find that the presence of Black GIs reduced prejudice significantly. The places where more African American soldiers were deployed during World War II contained fewer supporters of the far-right British National Party in 2009. People there display less implicit anti-Black bias and are more likely to report warmer feelings toward Black people. (U.S. troops were stationed in bases in the United Kingdom regardless of local racial attitudes.) The effects were particularly strong in rural, predominantly White areas where geographic mobility has been relatively limited. Direct contact with Black Americans may have shifted British attitudes in a more tolerant direction in the 1940s, with effects that have lasted for decades.

Protests can similarly affect public opinion. The political scientist Soumyajit Mazumder finds that White people who live in counties where the civil rights movement protested are less likely to harbor racial resentment against Black people, and more likely to support Democrats and affirmative action today. “The attitudes propped up by the Jim Crow racial order,” Mazumder writes, “can be reshaped through instances of nonviolent mobilization.” Other research finds that protests in an electoral district lead more people to vote and to donate to political candidates who share their ideological leanings. What’s more, protests tend to push legislators to vote more in line with protesters’ goals. Sustained collective action can create lasting social change.

We don’t yet know whether this summer’s Black Lives Matter protests will have a similar effect. But we do know that it’s possible to reduce prejudice in a way that lasts for generations; that protests can significantly change public opinion; and that major events can shape political attitudes long after the news cycle moves on. Since the George Floyd-inspired demonstrations may have been the largest in U.S. history, we should expect a lasting impact on American racial attitudes.

Bryan Schonfeld is a PhD candidate in politics at Princeton University.

Sam Winter-Levy (@SamWinterLevy) is a PhD candidate in politics at Princeton University.