Few academic ideas have been as eagerly absorbed into public discourse lately as “implicit bias.” Embraced by Barack Obama, Hillary Clinton and most of the press, implicit bias has spawned a multimillion-dollar consulting industry, along with a movement to remove the concept of individual agency from the law. Yet its scientific basis is crumbling.

Implicit-bias theory burst onto the academic scene in 1998 with the rollout of an instrument called the implicit association test, the brainchild of social psychologists Anthony...