Scientists believe brain scans could be used in the near future to detect whether a person is a racist or not.
Psychologists Tobias Brosch of the University of Geneva in Switzerland and Eyal Bar-David and Elizabeth Phelps of New York University examined activity in the brain while participants looked at pictures of White and Black faces.
Later participants performed a task that assessed their unconscious or implicit expression of race attitudes.
By examining patterns of brain activity in the fusiform face area - a brain area involved in face perception - the researchers were able to predict the race of the person that the participant was viewing, but only for those participants with stronger, negative implicit race attitudes.
This, the researchers said, implies that people with stronger, negative implicit race attitudes may actually perceive black and white faces to look more different than others who held no such prejudice.
These results suggest that it may be possible to predict differences in implicit race bias at the individual level using brain data, said Dr Brosch.
But Dr Phelps noted that further work would be needed before the technique could reliably detect whether people really were racists.