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.

Samuel L. Jackson, the actor, took umbrage last year when an entertainment reporter confused him with the actor Laurence Fishburne during a live television interview.

“Really? Really?” said Mr. Jackson, chiding the interviewer. “There’s more than one black guy doing a commercial. I’m the ‘What’s in your wallet?’ black guy. He’s the car black guy. Morgan Freeman is the other credit card black guy.”

And as a Washington correspondent, I managed a strained smile every time white officials and others remarked on my striking resemblance to Condoleezza Rice, then the secretary of state in the Bush administration. (No, we do not look alike.)