Can you say the hardest ever tongue twister?
5 December 2013 Last updated at 15:40 GMT
A team in the US have come up with what they believe to be the world's most frustrating tongue twister.
They found the most difficult phrase to say 10 times in a row at speed is:
Pad kid poured curd pulled cold
Dr Shattuck-Hufnagel from Massachusetts Institute of Technology (MIT) in Boston said the tongue twister is difficult to read because it doesn't make sense.
"In a jumbled up list of words you often get people trying to say two different sounds at the beginning of the words at the same time," she explained.
"Leap note nap lute" is another tongue twister that is difficult to read.