As a research tool, the IAT has fed close to 300 papers in fields ranging from neuroscience to marketing. It has also fueled academic challenge and debate, with a few social psychologists accusing the team of liberal bias and overinterpretation of the results. Some critics insist that the test does not really measure unconscious prejudice, only harmless cultural knowledge that differs from true racism. Psychologists argue over the underlying cognitive mechanism. One project found that some people will show bias just because they fear they will.

After finishing a meta-analysis across 61 studies, however, Greenwald and Banaji decided that the validity of the IAT holds. The test predicted judgments, behavior, and physiological reactions linked to stereotyping and prejudice better than expressed attitudes could. "In my own field, subtle prejudice, the IAT has helped crystallize ideas that we've been talking about for years," observes Jack Dovidio of the University of Connecticut. And it is an excellent teaching tool, he adds. When users experience their own discomfort and slowness in making associations, it is hard to ignore the message, agrees Princeton University social psychologist Susan Fiske. "Part of Mahzarin's genius was to see the IAT's potential impact on real-world issues," she points out.

Most recently, Banaji has been trying to discern when race attitudes first form and when conscious beliefs begin to diverge from those below the surface. In child-friendly tests, Banaji discovered that Japanese and white New England children as young as six both openly and implicitly preferred people like themselves. By age 10, their unconscious and conscious attitudes started to split. Despite expressing more egalitarian views as they grew older, people in the two societies continued to show automatic bias against black faces. For Japanese participants, both implicit and explicit attitudes toward European faces became more positive.

Banaji now suspects that if she could test for prejudice in babies, she would find it. But that does not mean that we are born with bias. Certainly we have the mental machinery to generalize and rank across social categories, she says, but culture fills in the necessary information. And humans absorb ideas about racial status early. In a study of 234 Hispanic-Americans, for instance, children compared themselves favorably with African-Americans. But when they used the IAT to compare themselves with white children, the natural preference for their own group fell away. "This work suggests that what we value, what we think is good, is in the air," Banaji remarks. It might develop through things like the warnings that a parent conveys to a child, in a tightening grip on a little hand. As adults, we continue to observe our environment and unintentionally adapt the stereotypes we hold to match.

Fortunately, our brains do not seem permanently stuck on bias. Powerful cultural signals push in one direction, but awareness, close relationships and experience can push back. Banaji, Greenwald and Nosek are starting a nonprofit to help people apply their research. They envision seminars and lectures, followed by "booster shots" of online exercises.

By weaving awareness into our day, Banaji states, we can help our conscious attitudes take charge. It is like exercising regularly and eating healthfully, she explained to the -filmmakers. And she suggested that they could build protective measures into their lives and work, much like fluoride in drinking water. "In every movie where you can do things counter to stereotype," she told them, "you are likely to produce change."

This article was originally published with the title The Implicit Prejudice.

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