Goodbye 'she sells sea-shells on the sea-shore', hello 'pad kid poured curd pulled cold' - quite possibly the hardest tongue twister ever created.
Although the phrase makes little sense, it was able to completely defeat volunteers taking part in a US speech study, researchers said.
Asked to repeat the phrase 10 times at speed, many of the participants simply stopped speaking altogether, according to lead researcher Dr Stefanie Shattuck-Hufnagel, from Massachusetts Institute of Technology (MIT) in Boston.
“If anyone can say this 10 times quickly, they get a prize,” she said.
The study was conducted to shed light on the brain's speech-planning processes. “When things go wrong, that can tell you something about how the typical, error-free operation should go,” said Dr Shattuck-Hufnagel.
Spoken too quickly, certain combinations of sounds appear to make people lose control of their mouths, with one sound often replacing another. For example, 'toy boat' becomes 'toy boyt', and 'top cop' becomes 'cop cop'.
Mistakes can also be more subtle the researchers found, with some of the time, tongue twister mix-ups appearing to be something in between the two sounds.
In the 'top cop' example, sometimes the 't' and 'c' seemed to be spoken almost the same time so that some of the word was lost, to become 't'kop'. Sometimes there was a delay between the two sounds with space for a vowel ('tah-kop').
The scientists studied two categories of tongue twister, simple lists of paired words, and whole sentences. Two word tongue twisters caused more 't'kop' type errors, while sentences produced more 'tah-kop' mistakes that included a short vowel after the initial consonant.
One possible clue to what is happening may be the regular rhythm of the word lists compared with the more irregular timing of the sentences, said Dr Shattuck-Hufnagel. But there appeared to be some overlap in the processes used to produce both types of speech.
The next stage of the research, data for which has already been collected, involved the MIT team and colleagues in Germany, placing tiny transducers on volunteers' tongues to measure their articulation.