People aren't the only ones who've got rhythm. Two reports published online on April 30th in Current Biology, a Cell Press publication, reveal that birds - and parrots in particular - can also bob their heads, tap their feet, and sway their bodies along to a musical beat. The findings show that a very basic aspect of the human response to music is shared with other species, according to the researchers.

"We've discovered a cockatoo [named Snowball] that dances to the beat of human music," said Aniruddh Patel of The Neurosciences Institute in San Diego, lead author of one of the studies. "Using a controlled experiment, we've shown that if the music speeds up or slows down across a wide range, he adjusts the tempo of his dancing to stay synchronized to the beat." One of Snowball's favorite dancing tunes is none other than the Backstreet Boys' "Everybody."

"For a long time, people have thought that the ability to move to a beat was unique to humans," added Adena Schachner of Harvard University, who led the other study. "After all, there is no convincing evidence that our closest relatives, chimpanzees and other apes, can keep a beat, and there is similarly no evidence that our pet dogs and cats can line up their actions with a musical beat, in spite of extensive experience with humans. In this work, however, we found that entrainment [to music] is not uniquely human; we find strong evidence for it in birds, specifically in parrots."

Before this discovery, "scientists who studied music and the brain thought that moving to a musical beat might be a uniquely human ability because we don't commonly see other animals moving rhythmically to music," Patel agreed. In fact, as far as they know, birds in the wild don't move in time with sounds, leaving many scientists to think that this ability might be an evolutionary specialization of the human brain for music cognition.

But that may not be so, the new studies suggest. They now suspect that the parrots' ability can be traced to another capacity they share with people: vocal learning or mimicry.

Indeed, Schachner's group searched YouTube for videos of dancing animals. Of more than 1,000 videos that turned up, only those of vocal mimics - representing 14 parrot species and one species of elephant - showed evidence that they could really get into the groove. That result is in keeping with the notion, first proposed by Patel, that entrainment to a musical beat relies on the neural circuitry for complex vocal learning, which requires a tight link between auditory and motor circuits in the brain, they said.

"A natural question about these results is whether they generalize to other parrots, or more broadly, to other vocal-learning species," including songbirds, dolphins, elephants, and pinnipeds, a group including walruses and seals, Patel said.

The findings in birds also offer new insight into humans' relationship to music.

"Why humans produce and enjoy music is an evolutionary puzzle," Schachner's team wrote. "Although many theories have been proposed, little empirical evidence speaks to the issue. In particular, debate continues over the idea that the human music capacity was not selected for directly, but arose as the byproduct of other cognitive mechanisms. By supporting the idea that entrainment emerged as a byproduct of vocal mimicry in avian species, the current findings lend plausibility to the idea that the human entrainment capacity evolved as a byproduct of our capacity for vocal mimicry."

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**To view two movies that correspond with this study, please visit the following embargoed link, which is also embargoed until 12 Noon EST on 30 April: http://www. cell. com/ current-biology/ April30Movie .

Article 1:

The researchers include Aniruddh D. Patel, University of California, San Diego, La Jolla, CA; John R. Iversen, University of California, San Diego, La Jolla, CA; Micah R. Bregman, University of California, San Diego, La Jolla, CA; and Irena Schulz, Bird Lovers Only Rescue Service, Dyer, IN.

Article 2:

The researchers include Adena Schachner, Harvard University, Cambridge, MA; Timothy F. Brady, Massachusetts Institute of Technology, Cambridge, MA; Irene M. Pepperberg, Harvard University, Cambridge, MA, Brandeis University, Waltham, MA; and Marc D. Hauser, Harvard University, Cambridge, MA.