It is not bias or bigotry, the researchers say, that makes it difficult for people to distinguish between people of another race. It is the lack of early and meaningful exposure to other groups that often makes it easier for us to quickly identify and remember people of our own ethnicity or race while we often struggle to do the same for others.

That racially loaded phrase “they all look alike to me,” turns out to be largely scientifically accurate, according to Roy S. Malpass, a professor emeritus of psychology at the University of Texas at El Paso who has studied the subject since the 1960s. “It has a lot of validity,” he said.

Image The white New York City police officer who arrested James Blake reportedly mistook him for this man, who was initially suspected of playing a role in a credit card fraud ring, according to the police. He is no longer a suspect in the case, police say.

Looking for examples? There is no shortage — in the workplace, at schools and universities, and, of course, on the public stage.

Lucy Liu, the actress, has been mistaken for Lisa Ling, the journalist. “It’s like saying Hillary Clinton looks like Janet Reno,” Ms. Liu told USA Today.