The death of George Floyd, an African-American man killed by White police officers in Minneapolis, Minnesota, on May 25, 2020, has reenergized the movement against police brutality-in the United States and across the globe. But this killing also highlights a disturbing puzzle: Why has violence against African Americans continued in the 21st century? The Emancipation Proclamation ended slavery in the United States in 1862, but African Americans continue to suffer deep injustices in the 21st century. Why is change toward equal justice so slow?Similarly, American women won the right to vote in 1920, but a century later we still have not had a woman in the White House. Women continue to be grossly underrepresented at the highest levels of business and politics, where the power lies. Why is change toward gender equality so slow? Moreover, why do women and minorities continue to face inequalities in so many different countries around the world?Questions about the painfully slow pace of change to end historic injustices place the spotlight on political plasticity, the speed and extent to which political behavior does (or does not) change (Moghaddam, 2018). For peace psychologists who believe that peace and justice are interconnected, political plasticity must become a more central focus of research and practice.Political plasticity concerns change at the collective level, a topic rarely addressed by psychologists. Brain plasticity is a major and fast-expanding research topic in several branches of psychology, but here the focus is on microlevel processes in neurons, neural networks, and brain functioning. Clinical psychologists, educational psychologists, and some other specialized groups are also concerned with behavioral change, but these usually concern change in individual behavior over relatively short-term periods, months and years rather than centuries. A small number of organizational and social psychologists have given attention to group-level change (e.g., Taylor & de la Sablonnière, 2014), but there is urgent need for more attention to be given to the psychological processes that underlie societal changes taking place, or failing to take place, over centuries and even thousands of years.A focus on political plasticity leads us to examine psychological processes underlying the changes that have (and have not) taken place since democracy was first formally introduced in Athens about 2,500 years ago. Athenian democracy gave voting rights to free men, not women and not slaves. About 2,300 years later, the American Revolution gave birth to a U.S. Republic that gave the vote to free men, not women and not slaves. It was not until the 20th century that women, African Americans, and other ethnic minorities gained the right to vote, and even now voter suppression continues to seriously hamper and limit ethnic minority participation in U.S. elections. The struggle to achieve justice and equality for women and minorities has been extremely slow, and psychological processes are central to this anguished and as yet unfini...