Psychologist Gordon Allport's 1954 book The Nature of Prejudice shaped how researchers study the topic. He argued that prejudice grows from rigid group categories and can be reduced by equal-status contact between groups working toward shared goals. That idea, called contact theory, informed school desegregation debates.
Prejudice alone does not explain racial inequality. A person can hold no conscious ill will and still take part in systems that harm people of color. That is why anti-racist work separates prejudice, an individual attitude, from racism, a system backed by power. Implicit bias research shows that prejudice can also work automatically, shaping split-second decisions in hiring, medicine and policing.
Prejudice matters because it becomes behavior. In a well-known 2004 study, economists Marianne Bertrand and Sendhil Mullainathan sent fake résumés to employers in Boston and Chicago. Résumés with white-sounding names received about 50% more callbacks than identical ones with Black-sounding names. Individual judgments, repeated across many decision-makers, add up to measurable gaps.