Schachner analyzed the videos frame-by-frame, using the same analyses applied to the case-study birds. Criteria included the animal's speed compared to the speed of the music and alignment with individual beats. Potentially "fake" videos were omitted, where music was added to the video after the fact, or the animal was following visual movement.
"The really important point is that many animals showed really strong evidence of synchronizing with the music, but they were all vocal mimics," says Schachner. "Most of them were parrots -- we found 14 different species of parrot on YouTube that showed convincing evidence that they could keep a beat."
Because only animals capable of vocal mimicry such as parrots appear to be able to keep a beat, the study implies an evolutionary link between vocal mimicry and this crucial part of dance.
"Our data suggests that some of the brain mechanisms needed for human dance originally evolved to allow us to imitate sound," says Schachner.
It is important to note that vocal mimicry alone is not enough for a bird to keep a beat, although the researchers aren't yet certain why some parrots can dance and not others. It may be that all parrots have a latent capacity, but need certain experiences or social motivation, according to Schachner.
Schachner says that these birds do not seem to move in synchrony with sounds in the wild, and so the behavior could not have evolved as a result of direct natural selection. For this reason, in bird species this capacity must be an evolutionary byproduct of something else, says Schachner, seemingly vocal mimicry.
It may be, says Schachner, that the human ability to keep time with music has also evolved as a byproduct of vocal mimicry. She points out that the cognitive proces
|Contact: Amy Lavoie|