Victims suffering serious speech disorders are able to sing complete texts with considerable fluency.
Until now, this astonishing observation has been explained by the fact that the right brain hemisphere, which supports important functions of singing, remains intact.
Singing was thought to stimulate areas in the right hemisphere, which would then assume the function for damaged left speech areas. A treatment method known as Melodic Intonation Therapy is based on this idea.
But researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, have now demonstrated that melody may not be the decisive factor, instead, rhythm may be crucial.
Moreover, highly familiar song lyrics and formulaic phrases were found to have a strong impact on articulation - regardless of whether they were sung or spoken.
The results may lead the way to new rehabilitative therapies for speech disorders.
The study found that singing was not the decisive factor for the patients. Singing the texts did not produce better results than speaking them rhythmically.
"The key element in our patients was, in fact, not the melody but the rhythm," said Benjamin Stahl, researcher at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig.
However, the level of familiarity with the song lyrics and whether the texts contained formulaic phrases was found to be even more important.