Viral videos of U.S. police officers beating and shooting black citizens have sparked a national conversation on how they interact with racial minorities. Such videos have also inspired law enforcement agencies to embrace body cameras to document those interactions. Now, a new study of body cam footage from Oakland, California, suggests that officers of all races consistently use less respectful language with blacks than with whites during traffic stops. The results—taken from more than 36,000 language snippets at nearly 1000 stops—could transform officer training, social scientists say.