The common perception that people from other racial groups look alike is rooted in the way human brains process what they see, researchers say.
It has long been known that people find it easier to tell apart members of their own race than those of a different race. But the mechanism behind this has been the topic of much research.
Now a new study backs up the idea that the phenomenon is rooted, at least in part, in visual and neural processes.
Nick Camp, the co-author of the research from Stanford University, said: “What it tells us is that our tendency to see members of our own [racial] group as individuals and de-individuate members of other racial groups, that is something that happens on sight.”
The team said the study was important as it showed that what human senses picked up was not necessarily an accurate representation of reality. That, they added, mattered since biases in perception could lead to harmful actions or behaviours – such as assuming one person’s behaviour was typical of all within that social group. It might also fuel errors ranging from inaccurate witness statements to embarrassing social mistakes.
The researchers, whose study has been published in the Proceedings of the National Academy of Sciences, reported how 20 white participants were shown a series of images including faces, numbers and objects, while they had their brains scanned using functional MRI – a technique that allowed the team to spot changes in activity.
In 19 of the 20 participants, a greater area of the face-recognition region was activated when the participants saw a white face compared with a black face. Six participants showed no activation at all in that region when presented with black faces.
The team then showed participants several series of images each composed of either six white or six black faces. The faces shown were engineered to have a certain level of physical similarity ranging from them all being identical to completely different.
For both black and white faces, brain activity increased as dissimilarity between the faces in the series rose – the team suggested this was because the images were perceived by the brain as more novel. However, this increase was more pronounced for white faces than for black faces. The researchers said that it suggested participants were better at picking up on physical differences between white faces – even for faces completely different to each other, brain activity was higher for white faces.
A further three experiments, outside of the scanners, involved participants rating how different they thought a series of faces of a given race were, whether two faces were different, and whether they had seen a given face before. The results showed that participants had a greater likelihood of rating black faces as more similar to each other – or having seen them before – than white faces, even if the faces of both races had been engineered to show the same level of similarity.
The study has limitations: only a small number of participants were involved, and the experiments only involved responses from white people.
The team also did not take into account how diverse participants’ social groups were – those with close friends from different racial groups would be expected to be more sensitive to facial differences in such groups.
The researchers said the findings could help to investigate ways to avoid harmful biases. Camp said some evidence suggested the phenomenon could depend on which characteristics were used to group people, for example if people were part of the same or rival sports team. He said: “Getting people to think about groups in different ways, or re-categorising individuals, might be an effective way of combating even these low-level perceptual biases.”
Dr Holger Wiese, an expert in face recognition at the University of Durhamwho was not involved in the research, described the study as elegant. He cautioned against linking the phenomenon to prejudice, noting it was not clear how or if it tied into stereotyping, which tended to be rooted in assuming personality or behaviours are universal within a group. He said: “We don’t know whether what they describe here is the basis for racial prejudice – the paper doesn’t say that at all.”
Dr Brent Hughes, a co-author of the paper from the University of California, Riverside, stressed that the biases reported in the study were not fixed.
He said: “Individuals should not be let off the hook for their prejudicial attitudes just because we see evidence of race biases in perception. To the contrary, these race biases in perception are malleable and subject to individual motivations and goals.”
