"They all look alike."
There may be something behind this age-old canard: Science indicates that people can have a hard time differentiating between faces of people whose race is different from their own.
But for black people, being mistaken for someone else can have a special sting, which may explain why the movie star Samuel L. Jackson had a tense exchange with (white) KTLA entertainment reporter Sam Rubin while promoting his new action flick, RoboCop - after the journalist appeared to confuse Jackson with Laurence Fishburne.
"We may be all black and famous, but we all don't look alike!" Jackson exclaimed. He proceeded to ridicule the reporter, refusing to move on despite profuse apologies.
It was a situation that's familiar to many groups in a diverse society conscious of demographic boxes.
Asian-Americans get confused with people who aren't even from their ancestral countries. Blondes get mistaken for other blondes who look nothing like them. Straight people accidentally call lesbians the name of the other lesbian they know.
"Americans have been socialised to place people in categories," said Josie Brown-Rose, an English professor at Western New England University. "Everything from a job application to a college application requires us to self-identify into racial groups and locate ourselves with in a specific collective."
"Oftentimes when we look at individuals, it is the collective that we see first."
Scientific studies have identified the "other race effect," in which people tend to confuse or incorrectly name individuals of other races, said Thomas Busey, an Indiana University psychology professor who studies face recognition.
Read: How the brain and facial recognition works
There are two theories for why this happens, Busey said.
One is that people focus on the wrong physical cues — hair colour and texture may be a good way to distinguish white people, for example, but it doesn't work so well for Asians.
The other theory is that people who have little contact with other races are more likely to think they all look the same.
"If we have less contact with other races, we're less likely to learn the real cues," Busey said.
He has fallen victim to the "other race effect" himself: Once, Busey was 20 minutes into a conversation with one of his black students when he realised he thought she was the only other black person in the class.
Yet Busey has made the same kind of error with a white student. Which raises questions about why Jackson reacted so strongly, and whether it was an innocent mistake when TV reporter Sam Rubin confused Jackson with Fishburne.
The two actors share little physical resemblance except for being large African-Americans with a gap between their front teeth. Did Rubin really think Jackson, known for his hard edge and foul mouth, was Fishburne, whose persona is more Shakespearean?
COULD YOU MISTAKE US FOR EACH OTHER?
Would Rubin have confused Tom Cruise and Mel Gibson?
Despite Rubin's apologies on air and then online for what he himself called a "very amateur mistake," it's easy for some to see race as the reason.
Black people must navigate white environments far more often than whites find themselves surrounded by non-whites, so it can feel like black people get misidentified more often.
Just among current black celebrities, the E! channel confused the actresses Viola Davis and Octavia Spencer; George Stephanopolous thought basketball legend Bill Russell was actor Morgan Freeman; and a picture of Seal, the slim singer with a scarred face, was displayed by a TV station when the huge, unblemished actor Michael Clarke Duncan died.
Not to mention when pop star Will.i.am was called Wyclef Jean on live TV. The reporter quickly put a hand to his earpiece and corrected himself — but with another wrong ID: the rapper Wale.
"I could understand where Sam gets mad at this," said Mark Anthony Neal, an African-American studies professor at Duke University who focuses on pop culture.
"It's a big deal because it erases your achievements. You're just another interchangeable Negro actor," Neal said. "Your body of work does not stand out enough to see what you've done is unique and distinct from what they've done."
Read: You look familiar: how Malaysian Chinese recognise faces
Neal said Fishburne is an incredible actor but with the exception of Fishburne's starring role as Morpheus in The Matrix films, Jackson is a much bigger, more prolific movie star.
"If you're Sam Jackson," Neal said, "given how much he's worked, you're thinking: I've been doing all this for all this time, and you still think I'm somebody else?"
It was not the first time Jackson had been confused with Fishburne — although previously it was a spoof that mocked racial sensitivities and the idea that black people look alike.
In a 2005 episode of Ricky Gervais' comedy Extras, a white woman on the set of a fictional film tells Jackson — playing himself — that she loved him in The Matrix.
Gervais tries to ride to the rescue: "I know what you're thinking. It isn't that you all look alike."
"If that's what you were thinking," continued Guy Ritchie - sorry, Ricky Gervais.
A blow to the head can cause a number of strange afflictions, including not recognising your mom
Romance across the race divide - it's completely normal
How your online persona reveals your personal identity
By Jesse Washington for The Associated Press.
Image: Samuel L Jackson by s_bukley from Shutterstock