I came across this article about a recent study done exploring the difficulty of recognizing differences among people of other racial groups. According to the author, Kate Shaw, this new study helps explain why it is that we have an easier time distinguishing people's faces when the people are from our own racial group. But from what she goes on to say about it, it does nothing of the sort.
What this study shows, if the research is accurate, is (1) the effect occurs and (2) there's a biological mechanism involved. They've identified, from having subjects look at faces, a tendency to have a harder time distinguishing differences among faces that belong to people who are members of a different race from the person doing the looking. They've also identified an electrical effect in the brain that, according to this article, is triggered by the sight of a human face. The effect decreases in subsequent viewings of the same face, and this is called repetition suppression. The repetition suppression effect occurred with faces of the same race but not with faces of another race.
But is this an explanation? Hardly. All it does is show that there is a neurological explanation. It shows that this effect occurs with same-race faces but not with other-race faces. It doesn't explain why that's true. It doesn't explain why the repetition suppression effect occurs with same-race faces but not with other-race faces. So it doesn't really explain why this biological response occurs, and therefore it doesn't explain, as this article was claiming, why we have an easier time distinguishing faces of people in our own race than with people of other races. For that we'd need an explanation of why this particular neurological effect, with certain repeated faces, decreases or why, with other faces, it doesn't. This study, at least from what I see in this article, hasn't even attempted to explain that, and that's the interesting question.