London - Forget Peter Piper and his peck of pickled pepper – psychologists have created what could be the most frustrating tongue twister.

It may not make much sense, but the phrase “pad kid poured curd pulled cold” completely defeated volunteers in a US speech study.

Asked to repeat the phrase ten times at a fast lick, many of the participants clammed up and stopped talking altogether, according to lead researcher Dr Stefanie Shattuck-Hufnagel, from Massachusetts Institute of Technology in Boston.

The study, presented at the annual meeting of Acoustical Society of America in San Francisco, was conducted to shed light on the brain’s speech-planning processes.

The scientists studied two categories of tongue twister – lists of paired words, such as “top cop”, and whole sentences.

They found that in the word lists there were mainly “t’kop” type errors, while sentences produced more “tah-kop” mistakes with a short vowel after the initial consonant. - Daily Mail