Tongue-twisting ties between parrots and humans

Scientists around the world finally have the answer to one age-old question:\n"Polly want a cracker?"\nWell ... almost. More accurately, the question might be, "Can Polly really talk?"\nAnd thanks to the work of a few IU-associated scientists, researchers have gained insight into the parallels between human and parrot vocalizations. As a result, doctors are gaining a better understanding of what causes and how to treat human speech disorders. \nBirds, unlike most other animals, have to learn to make the correct sounds to communicate with their species, said Rod Suthers, an IU professor of physiology and biophysics who supervised the experiment.\n"A robin has to learn to sing like a robin, not a blue jay," Suthers said. "This is important because each species uses its vocalization for communication. A (human) child has to learn to make the sounds of its language."\nThis is just one attribute that both birds and humans share when it comes to vocalizations, since most animals do not have to learn how to communicate or learn a language. Parrots, however, take that parallel one step further. \n"It was generally believed that birds do not use vocal-tract structures to generate complexity in their vocalizations," said Gabriel Beckers, a former post-doctoral research fellow at IU and the lead author in the experiment. "But it was suspected that parrots might form an exception."\nParrots are different from song birds due to their unusually thick and muscular tongues, Suthers explained. Until recently, he said, it was unknown whether this tongue played a role in parrot vocalization.\n"(Parrots) are able at mimicking speech," said Beckers, who is currently a fellow at the Leiden University in the Netherlands. "Second, tongue movements are observed when they vocalize. However, direct evidence that tongue placement influences acoustic characteristics in vocalizations was lacking."\nFor this reason, Beckers, Suthers and IU graduate student Brian Nelson set out last year to see just how closely parrots' vocalization resemble that of humans. \nThe government supplied the trio with five deceased monk parrots from Florida. This particular species of parrots from South America was introduced to the southern United States and overpopulated the area. Beckers said he was able to receive the five parrots from the government's eradication program. \nThey replaced the syrinx, a vocal organ in birds found at the base of the trachea in the throat, with a tiny speaker normally used in hearing aides. Beckers played a sound through the speaker containing all frequencies between 500 and 10,000 hertz. Suthers explained that the frequency of sound is determined by the rate at which the vocal organ vibrates. \nBeckers said they recorded the sound normally generated by the syrinx as it came out of the parrot's mouth. \nThey discovered that small movements of the parrot's tongue greatly influenced the parrot's vocalization.\n"(Beckers') work is the first to quantitatively show that the position of the tongue can change the form and structure of parrot vocalizations," Suthers said. The influence this discovery could have on humans, Beckers explained, is large.\n"Bird vocalization is regarded by scientists as an innovative animal model system for human speech," Beckers said. "Now that we established that parrots use their tongue to generate vocal complexity, the parallels between human speech and bird vocalization are even more close than we thought."\nThis uncanny relationship between parrot and human vocalization was part of the reason the National Institute of Health decided to fund the experiment, Suthers said. With more studies illustrating the similarities between how a bird's brain and a human's brain control vocal communication, the institute hopes it will have a better understanding of what causes certain speech disorders. \nIn the future, Beckers hopes to have the opportunity to develop his own research program to further his studies. As for now, the report of this recent experiment is featured in the Sept. 7 issue of Current Biology magazine.\n-- Contact staff writer Katie O'Keefe at kjokeefe@indiana.edu.