RUTHFULLY YOURS

In the race IAT (there also versions for everything from gender to disability to weight), test-takers at a computer are asked to press two keys to sort a series of black and white faces and a set of “good” and “bad” words. For part of the exercise, the test-taker presses one key for white faces and words like “happy,” and the other key for black faces and words like “death.” Then the protocol is reversed, pairing white faces with “bad” words and black faces with “good” words. (The order is randomized, so some test-takers sort black faces with “good” words first.)

A majority of test-takers—including about 50% of blacks, according to some accounts—are faster at the sorting game when white faces are paired with good words. This difference is said to represent an “implicit bias” in favor of whites that can explain racial disparities in society.

Mr. Greenwald and Ms. Banaji did not pioneer response-time studies; psychologists already used the methodology to measure how closely concepts are associated in memory. And it’s widely accepted in psychology that automatic cognitive processes and associations help people navigate daily life. But Mr. Greenwald and Ms. Banaji, now at the University of Washington and Harvard, respectively, pushed the technique into charged political territory. Not only did they confidently assert that any differences in sorting times for black and white faces flowed from unconscious prejudice, they claimed that the implicit bias allegedly measured by the IAT could predict discriminatory behavior. In the final link of their causal chain, they argued that this unconscious and pervasive predilection to discriminate is a powerful cause of racial disparities.

As they wrote in “Blindspot,” their 2013 best seller: “Given the relatively small proportion of people who are overtly prejudiced and how clearly it is established that automatic race preference predicts discrimination, it is reasonable to conclude not only that implicit bias is a cause of Black disadvantage but also that it plausibly plays a greater role than does explicit bias.”

If these sweeping claims were correct, every personnel decision could be challenged as the product of implicit bias. The pressure to guarantee equality of outcome through quotas would grow stronger. But the politics of the IAT had leapfrogged the science behind it. Core aspects of implicit-bias doctrine are now under methodological challenge.

A person’s IAT score can vary significantly each time he takes the test, undercutting its reliability as a psychological instrument. Test scores have almost no connection to what IAT research ludicrously counts as “discriminatory behavior”—trivial nuances of body language during a mock interview, say, or a hypothetical choice to donate to children in Colombian slums rather than South African ones.

Mr. Greenwald and Ms. Banaji now admit that the IAT does not predict “biased behavior” in the lab. (No one has even begun to test its connection to real-world behavior.) The psychometric problems associated with the race IAT make it “problematic to use to classify persons as likely to engage in discrimination,” they wrote, along with a third co-author, in 2015.

Although most of the psychology profession initially accepted the startling claim that the IAT reveals a predilection to discriminate in real life, possible alternative meanings of a “pro-white” score have since emerged. Older test-takers may have cognitive difficulty with the shifting instructions. The association of black faces with negative words may reflect an awareness of socioeconomic realities. Greater familiarity with one racial group over another could affect reaction times. These alternative meanings should have been ruled out before psychologists announced that a new “scientific” test had revealed the ubiquity of prejudice.

Nevertheless, the idea of implicit bias has marched through American institutions. This summer nearly 200 CEOs signed a pledge to pack their employees off to implicit-bias training, part of an economywide diversity initiative championed by PricewaterhouseCoopers. Plaintiffs in employment discrimination cases regularly try to introduce implicit-bias research into their lawsuits.

President Obama sent federal law-enforcement personnel to implicit-bias training; many local police departments are doing the same, spending millions of dollars that could be used instead to improve officers’ tactical and communication skills.

Faculty hiring committees routinely have to take the IAT to confront their hidden biases against minority and female candidates. College students are being encouraged to take it as well. UCLA’s vice chancellor for equity, diversity and inclusion, Jerry Kang, has argued for federal regulation of local news coverage, especially crime stories, to lessen implicit prejudice.

The need to plumb the unconscious to explain racial gaps arises for one reason: It is taboo to acknowledge that socioeconomic disparities might be caused by intergroup differences in cultural values, family structure, interests or abilities. The large racial gap in academic skills renders preposterous any expectation that, absent bias, blacks and whites would be proportionally represented in the workplace. And vast differences in criminal offending are sufficient to explain racial disparities in incarceration rates.

In light of such realities, the minute distinctions of the IAT are a sideshow. America has an appalling history of racism and brutal subjugation, and the public should always be vigilant against any recurrence of that history. But the most influential sectors of the economy today employ preferences in favor of blacks. The main obstacles to racial equality now lie not in bias but in culture and behavior.

Ms. Mac Donald is a fellow at the Manhattan Institute. This article is adapted from the Autumn issue of City Journal.