It might sound contentious, but many studies have indicated that people are generally worse at distinguishing between the faces of individuals of ethnicities other than their own. The underlying cause of this so-called other-race effect (ORE) has been the subject of debate for decades – although new research suggests that the phenomenon may have less to do with prejudice and more to do with cognitive processes such as “perceptual expertise.”

On the face of it, an impaired ability to tell people of certain races apart might seem like nothing more than bigotry. However, an alternative argument holds that this lack of recognition may come down to mere unfamiliarity. 

Such a hypothesis rests upon the fact that most of us are in fact pretty rubbish at recognizing faces that don’t quite match our learned expectations. As evidence for this, scientists often point to the face inversion effect (FIE) paradigm, whereby people consistently struggle to identify faces that are presented upside down. 

Previous studies have demonstrated that this FIE discrepancy is often greater when looking at people of one’s own race than when observing other ethnicities. In other words, the impairment caused by viewing a face upside down is less pronounced if that face is of another race, probably because we aren’t very good at recognizing them in the first place.

Writing in the journal Scientific Reports, a team of researchers sought to take this argument a step further in order to determine whether the ORE can be explained by perceptual expertise. To do so, they asked 96 White European volunteers to take part in a face recognition challenge involving both upright and inverted faces, half of which were White European while the other half were East Asian.

To complicate matters, the researchers zapped participants’ prefrontal cortices using transcranial direct current stimulation (tDCS), disrupting their ability to recognize faces. Importantly, however, only half of these recruits received a full dose of brain-boggling electricity, while the other half were supplied with a degree of tDCS that was too small to actually affect their perception.

Compared to those whose powers of discernment were unaffected, participants who got the full whack of tDCS displayed a significantly reduced FIE when observing faces of their own race. According to the study authors, this occurred because the electrical brain stimulation eliminated the perceptual expertise component for upright own-race faces, thus decreasing the difference in capacity for recognizing upright and inverted faces.

“Importantly, the anodal tDCS did not reduce the FIE for other-race faces supporting the hypothesis that there is less perceptual learning to be lost for those faces,” add the researchers. This, they say, provides strong evidence for the argument that our facial recognition capacities are largely determined by cognitive expertise, and not by racial preconceptions.

Summarizing these findings, study author Dr Ciro Civile explained in a statement that “when you systematically impair a person's perceptual expertise through the application of brain stimulation, their ability to recognize faces is broadly consistent regardless of the ethnicity of that face.”

As such, the researchers conclude that “our findings would suggest that perceptual expertise can fully explain the differences in the size of the FIE found previously for own versus other-race faces.”