Birds boogie away the notion that rhythm is reserved for just us
Thrashing his mohawk up and down and kicking his feet in time to a rock anthem, Snowball the headbanging cockatoo is turning the notion of what's human on its head.
Scientists have long wondered whether the ability to dance to a beat is uniquely human - and why it evolved in the first place. Now, two unusual scientific studies that relied on YouTube videos of dancing animals, the musical stylings of the boy band the Backstreet Boys, and two grooving parrots, have furnished evidence that people aren't the only ones able to boogie and two-step.
A painstaking analysis of thousands of videos revealed that 14 species of parrot have rhythm.
"When I was first starting this work, I was very skeptical. There are all kinds of ways these birds could be faking or cheating," said Adena Schachner, a Harvard University psychology graduate student and lead author of a study published yesterday in the journal Current Biology. But the more she watched YouTube videos of dancing parrots, the more she began to wonder: "How can we make sure this phenomenon is real?"
Schachner's and the other scientists' work has a serious side: By studying other animals, they hope to gain insight into the evolution of an ability that is a cornerstone of human behavior and culture.
The finding that parrots can dance to an external beat supports an emerging theory on the origins of dance - that it might be a byproduct of another skill parrots share with humans, the capacity to mimic sounds.
Dr. Oliver Sacks, a noted Columbia University neurologist and author, contended in the hardcover version of his book "Musicophilia" that the ability to synchronize movement to a rhythm was uniquely human. In response, readers who disagreed began sending him videos of Snowball, and he was convinced to revise the paperback edition. He called the two studies published yesterday "very good, meticulous, and fascinating."
"Clearly, moving in synchrony is an essential and universal part of human culture," Sacks said in an interview yesterday. "My own suspicion is [dancing] may become selected and reinforced in our species, because it's a biological advantage to bond people. . . . It may be this thing which arose as a side effect of our speech."
To test whether parrots can actually dance to a beat, Schachner and her adviser, Harvard psychologist Marc Hauser, teamed up with Irene Pepperberg, a Brandeis University psychology professor who for three decades studied an African grey parrot named Alex with remarkable language abilities. They played riffs of drum beats for Alex that he had never heard before, and everyone in the room stayed perfectly still.
To Schachner's surprise, Alex (who's since died) started dancing - ducking and bobbing his head in time to the music.
A frame-by-frame analysis of his movements found that his head bobs were in sync with the beat. The scientists calculated that there was less than a 1 in a 100 million chance the timing was the product of random chance.
Next up was Snowball, a sulphur-crested cockatoo from Indiana who has become a YouTube celebrity for his ability to rock out to everything from Queen to Stevie Nicks.
Using the same frame-by-frame analysis, researchers watched Snowball kick his feet in the air and bob his head in time to music with many tempos and found that, like Alex, he had rhythm.
A second study published in the same journal yesterday tested Snowball's ability to follow a variety of beats, by speeding up and slowing down his favorite song, "Everybody," by the Backstreet Boys. The researchers, based at the nonprofit Neurosciences Institute in San Diego, found that Snowball was actually able to synchronize his movements to a rhythm and wasn't just bopping up and down arbitrarily.
To test whether the ability to dance had something to do with animals' ability to mimic sounds, the Harvard researchers then subjected nine cotton-top tamarin monkeys to the same experiment they did on Alex. The monkeys, which are not vocal mimics, but are more closely related to humans, were wallflowers.
Finally, they took their theory to the Web, systematically searching for animal dancing videos on YouTube. Fifteen species seemed to have the ability to dance, and all were capable of imitating and learning sounds they hear - 14 species of parrot and the Asian elephant. Meanwhile, dogs, ferrets, horses, sea lions, cats, squirrels, and fish depicted as "dancing" all failed to dance in time to an external beat.
The results support the theory that dance may be a skill that becomes possible as a byproduct of vocal mimicry. Researchers think that perhaps the brain circuits necessary for vocal mimicry and learning may also enable people - and birds - to move with the music. Both talents seem to require careful monitoring of environmental sounds and matching them with a movement.
"It's more than just responding to a sound. The animal might move when it hears a sound, but if you are dancing along to a song, if you clap your hands along with the song, the place where the beat comes, where you clap your hand isn't 100 percent easy to identify," said Virginia Penhune, a psychology professor at Concordia University in Montreal who was not involved in the study. "Most people would have said this is something only human beings can do, because there's no evidence for any animals doing this in the wild."
Why don't parrots dance in the wild? Birds might not have needed to use the latent ability to move to a beat, Penhune pointed out, because there aren't many sounds in nature like human music, with its periodic, regular rhythms. For humans, on the other hand, dancing might have provided an evolutionary advantage, because it was useful for bonding and communication.
John Iversen, a theoretical neurobiologist at the Neurosciences Institute, said that he and his colleagues had been searching for animals that had rhythmic dancing abilities for some time, going as far as Thailand to check out elephants, and talking to people who participated in dressage events.
Meanwhile, under their noses on YouTube was Snowball, whom the team is now scrutinizing further. His owner, Irena Schulz, reports that Snowball continues to come up with new dance moves.
His latest? Blowing kisses in time to the music.
Carolyn Y. Johnson can be reached at cjohnson@globe.com. 
