London, November 12 : A study conducted at the University of California in San Diego has confirmed that a spoken phrase seems to morph into a song when repeated, throwing new light on the difference between speech and song.
Lead researcher Diana Deutsch, a psychologist at the university, says that she first observed this effect while recording her own voice in the mid-Nineties.
She has revealed that one phrase behaved so strangely that it began to sound like a song, upon being replayed several times.
In her latest study, Deutsch tested the illusion on proficient singers.
The participants were asked to play the phrase just once, and to repeat what they had heard.
The research team observed that the phrase was sung back by those who had heard it several times.
Deutsch points out that the illusion occurs only when the phrase is repeated exactly.
"It brings to the fore a real mystery - why don't we hear speech as song all the time?" New Scientist magazine quoted her as saying.
She believes that the brain usually suppresses musical cues when a person hears speech, and that helps the individual focus on interpret the words.
However, a repetition of the words already processed by the listener may sometimes have an overriding effect on the process of suppression of musical cues.
"It stops the inhibition of the pitch region of the brain so we hear song, which is really what we ought to have been hearing in the first place," says Deutsch, who will discuss her findings next week at an Acoustical Society of America meeting in Miami, Florida.
She and her colleagues are presently using MRI scans to see which brain regions "light up" when people perceive a shift from speech to song.