Their study, published in the journal Psychological Science, found the 7 percent of people that showed no racial bias differed from biased individuals in a fundamental way -- they also were less likely to form negative emotional associations in general.

Robert Livingston of Northwestern University and Brian Drwecki of the University of Wisconsin asked white college students to do tasks that repeatedly paired unfamiliar Chinese characters with positive or negative images such as puppies or snakes. The results showed non-biased individuals were less likely than biased individuals to acquire negative emotions toward the character paired with negative pictures.

"Just as it is difficult to change visceral reactions to aversive foods -- for example lima beans -- through sheer force of will, it may also be difficult to change visceral attitudes toward racial groups by acknowledging that prejudice is wrong and wanting to change," Livingston says.

While reason may not change negative associations, Livingston and Drwecki argue negative associations could be reconditioned through positive interpersonal experiences or exposure to positive images of people of other races.