In a series of scathing critiques, some psychologists have argued that this computerized tool, the Implicit Association Test, or I.A.T., has methodological problems and uses arbitrary classifications of bias. If Barack Obama’s victory seemed surprising, these critics say, it’s partly because social scientists helped create the false impression that three-quarters of whites are unconsciously biased against blacks.

The I.A.T., which has been taken by millions of people on an academic Web site, measures respondents’ reaction times as they follow instructions to associate words like “joy” or “awful” with either blacks or whites. It generally takes whites longer to associate positive words with blacks than with whites, although some do show no bias. (To meet one of these exceptional cases, go to TierneyLab, at nytimes.com/tierneylab.)

The test is widely used in research, and some critics acknowledge that it’s a useful tool for detecting unconscious attitudes and studying cognitive processes. But they say it’s misleading for I.A.T. researchers to give individuals ratings like “slight,” “moderate” or “strong”  and advice on dealing with their bias  when there isn’t even that much consistency in the same person’s scores if the test is taken again.

“One can decrease racial bias scores on the I.A.T. by simply exposing people to pictures of African-Americans enjoying a picnic,” says Hart Blanton, a psychologist at Texas A&M. “Yet respondents who take this test on the Web are given feedback suggesting that some enduring quality is being assessed.” He says that even the scoring system itself has been changed arbitrarily in recent years. “People receiving feedback about their ‘strong’ racial biases,” Dr. Blanton says, “are encouraged in sensitivity workshops to confront these tendencies as some ugly reality that has meaning in their daily lives. But unbeknownst to respondents who take this test, the labels given to them were chosen by a small group of people who simply looked at a distribution of test scores and decided what terms seemed about right. This is not how science is done.”

Two of the leading I.A.T. researchers, Anthony Greenwald of the University of Washington and Mahzarin Banaji of Harvard, say that some of the past criticism about their measurement techniques has been useful. But they dismiss most of the current objections as moot because the I.A.T.’s validity has been confirmed repeatedly.