Claude Steele (who is, as it happens, Shelby Steele’s twin brother) falls on the cusp between the first two groups, as his book “Churn” makes plain. “Churn” is a sturdy word, unsubtle. The author uses it to describe “the mental agitation and physical stress” people can experience “in diverse settings”—particularly those in which there’s a “threat of being judged and treated badly based on negative feelings or stereotypes about our identities.” Picture a black student in a mixed-race math class, where a stereotype that black children struggle with STEM subjects can lurk in the minds of those who aren’t black.