When you have a harder time recognizing or distinguishing between members of racial ethnic groups other than your own, what's at work is known as the "cross-race effect."
One cross-race effect theory on racial mix-ups is what's called the "experience-based" hypothesis: We find it easier to recognize and distinguish and remember faces of our "racial in-group" than we do "racial out-groups" simply because we see the in-group features more.
Then there's the related "coding" or "categorization" hypothesis: When we see a member of another race, our minds pay more attention to what makes the person an out-group member than to his or her individual features. We lose some of the distinguishing details in the process.
All you niggas look the same 25 votes
All Eurpoeans look alike
All Africans look alike