Scientists from the Massachusetts Institute of Technology (MIT) have come up with a string of words so difficult that test subjects couldn't even finish it.
"If anyone can say this 10 times quickly, they get a prize," said MIT psychologist Stefanie Shattuck-Hufnagel when she presented her team's work at a meeting of the Acoustical Society of America.
Dr Shattuck-Hufnagel and her colleagues didn't invent the tongue twister just to laugh at people trying to say it.
Mistakes caused by tricky phrases offer insights into how the brain processes speech.
"When things go wrong, that can tell you something about how the typical, error-free operation should go," Dr Shattuck-Hufnagel said.