Psychologists Anthony Greenwald and Mahzarin Banaji developed the idea in the 1990s. In 1998, they and Brian Nosek introduced the Implicit Association Test, which measures how quickly people link groups with positive or negative words. Millions of people have taken it online through Project Implicit. Researchers still debate how well individual test scores predict behavior.
Studies of real decisions show bias at work. In a widely cited 2004 study, economists Marianne Bertrand and Sendhil Mullainathan sent fake resumes to employers. Resumes with white-sounding names got about 50 percent more callbacks than identical ones with Black-sounding names. A 2016 study found that about half of white medical students and residents surveyed held at least one false belief about biological differences between Black and white people, such as thicker skin. Those who held such beliefs rated Black patients' pain lower.
Implicit bias training became common in police departments and companies, but research has found it rarely changes behavior on its own. Many experts say structural changes, such as clear decision rules and accountability, work better.