(FOXNews.com) -- Those seven silver snakes should step to the side.
A nonsense string of words devised by MIT researchers investigating speech errors and brain functions proved so difficult that no test subjects could repeat the phrase -- clearly marking it as the world's toughest tongue twister.
The phrase was "pad kid poured curd pulled cod." When volunteers tried it, according to MIT psychologist Stefanie Shattuck-Hufnagel, some of them simply stopped talking altogether.
"If anyone can say this [phrase] ten times quickly, they get a prize," she said.
Shattuck-Hufnagel plans to present the tongue-tripping line along with her research into "alternating repetitive tongue twisters" at the 166th meeting of the Acoustical Society of America Thursday in San Francisco.
To study the challenging combinations of words, Shattuck-Hufnagel and colleagues recorded volunteers saying combinations of words that fell into two categories: simple lists of words, such as "top cop," and full-sentence versions of the same sounds with an inversion, such as "the top cop saw a cop top."
They found that in the word list tongue twisters, there was a preponderance of errors in which the "t" and the "c" seemed to arrive almost at the same time -- making a "t'kop" sound. In contrast, the sentence twisters induced more errors in which there was a delay between the two letters, with space for a vowel: "tah-kop."
The fact that both types of errors occur for sentences as well as word lists suggests that there is some overlap between the brain processes used to produce these two types of speech, Shattuck-Hufnagel said. "You can get both kinds of errors in both kinds of planning," she said.
Take that, Peter Piper.
To read more: FOXNews.com