Guest op-ed by Betsy Levy Paluck @ WashingtonPost.com, Dec. 12. (She is a professor of psychology and public and international affairs, and the deputy director of the Kahneman-Treisman Center for Behavioral Science & Public Policy, at Princeton University.)

In early June 2020, as Black Lives Matter protests flowered across the United States following the murder of George Floyd, businesses and other institutions rushed to enhance their diversity efforts. Chief diversity officer hires tripled among the largest publicly traded companies, enhancing diversity, equity and inclusion offerings for which U.S. companies paid an estimated $3.4 billion to outside firms that year.

What have we achieved with all this effort? In 2022, this question has special significance, as measures to increase diversity and racial equity have come under political attack, often by people who believe those shouldn’t be goals in the first place. But even among people who believe in the basic mission, common questions about diversity training have shifted from “Which training is best?” to “Is the training even a good idea?” and “Does the training have negative effects?”

The problem is that the real answer to all three of these questions is: We don’t know. As a behavioral scientist who studies prejudice and behavior change, I can tell you that the situation really is that bad [....]