Birds Can Dance, Video and Q&A with Harvard's Adena Schachner

April 30, 2009

Birds, and particularly parrots, have rhythm and can dance in time to musical beats just as we humans can, according to a pair of new studies in the latest Current Biology. More information is at Discovery News.

An emerging star in the bird dance world is Snowball, a sulphur-crested cockatoo. He can get down to any song with a strong, prominent beat.

Adena Schachner, a Harvard University researcher who led one of the studies on bird dancing, recently took time to discuss Snowball and related subjects with me. Here's a transcript of the interview:

JV- Did the birds that you studied ever learn their movements by watching someone else dance? I noticed that in the videos, the birds often stopped and looked at the filmmaker, so I'm curious if they were somehow attempting to use dance as a form of communication.

AS- This is a very interesting question. Although our work shows that the capacity for vocal imitation seems to be necessary for keeping a beat, we don't know yet what other types of experiences or capacities might also be needed!  You've hit on a few here: social experience with humans, motor imitation (imitating movements), and a close social bond with a human individual.

One thing we've noticed is that not all parrots dance-- and speaking anecdotally, the ones that do dance seem to have extensive contact and close social bonds with humans. It may be that these birds were motivated to dance by watching humans do so, and receiving positive social feedback-- we don't know yet, but this is a good possibility. 

However, the really important thing to notice here is that this type of social contact and exposure doesn't seem to be the main critical factor for entrainment. Even though many types of animals have extensive contact and close social bonds with humans, not all of these animals can dance in synchrony with a musical beat.  Think of dogs or cats -- Even after years of exposure and even (in some cases) professional training, it just doesn't look like they can do it.  So it seems like this type of social contact isn't enough-- in order to keep a beat, we also need the capacity for vocal imitation. 

JV- The studies found that animals who are "vocal mimics" appear to also have dancing skills. Does vocal mimicry always refer to an individual's ability to copy the vocalizations of another species, or can it also refer to an individual's ability to copy vocalizations made by conspecifics? Please also briefly explain how elephants, bats, cetaceans and pinnipeds exhibit vocal mimicry. I wasn't aware elephants had this talent, but your study suggests they do.

AS- In this paper, we use a really broad definition of vocal mimicry. We include both types of animals you mention-- those that can copy the sounds of other species, and those that can only copy sounds that are naturally produced by their own species.  There are also other differences between vocal mimics: for instance, some songbirds can only imitate sound when they are juveniles, and lose the ability in adulthood. Other animals, such as parrots, maintain the ability to learn vocalizations throughout their lives.  It may be that this sort of open-ended, flexible vocal mimicry is the kind that is needed. We hope that future work can tease apart these ideas!

With regard to vocal mimicry in other animal species, there are published scientific papers in all of these species showing some form of vocal imitation.  For example, one paper in Nature by Poole and colleages showed that a colony of elephants living near a road began to imitate the sounds of the trucks going by!  Some of the work on vocal mimicry in these species is cited in our Current Biology paper.

JV- Do you think some birds dance better than others, just as some humans appear to be more rhythmically inclined? It's interesting how one of your birds was quite a "toe-tapper," while the other was more into head bobbing.

AS- Yes, it may be the case that we see individual differences in skill at keeping a beat in birds, like we see in humans.  It seems that not all parrots dance-- even if Snowball the cockatoo dances, this doesn't imply that every member of his species will also respond to music with rhythmic movement!  This raises the question of what other types of experiences or capacities are needed to allow keeping a beat; and also whether there are true individual differences in dancing ability between birds of the same species.

With regard to the different types of movement, we thought it was incredibly interesting that Snowball had the capacity to move multiple body parts to a beat-- not just his head, but also his feet.  This type of flexibility makes the birds' dancing seem a lot like human dance.

(Another bird gets down to the Red Hot Chili Peppers)

JV- Why do you think birds respond more favorably to certain songs and musicians, just as we do? Did you notice if certain types of music, or even particular singers/groups appealed more to animal dancers than others? It looked like both of your birds danced to hip hop type music, for example, so I'm wondering if those sorts of rhythms held greater appeal for your test subjects. (I also have in mind another recent study on music, where human listeners were able to link the rhythm of a person's native spoken language to musical beats.)

AS- I have two main comments on this, both of which are very speculative! We need more work to really know if these are true.

My speculation is that birds might not be as good at perceiving a musical beat as humans are.  Some human music has a really clear, strong beat (like hip-hop, or a march with a strong base drum).  Other human music, for instance some more mellow pieces, still have a musical meter or pulse, but the strong beats aren't emphasized as much; they might not actually be louder than the other beats, for instance. It may be that birds need a really clear, strong beat in order to 'find the beat' in the first place. But we'll need more work to see if this is the case.

My other anecdotal impression is that these birds may indeed have musical preferences in a way similar to the way people have musical preferences.  We already know from experimental work (by Watanabe in 1998) that Java sparrows do have spontaneous musical preferences, for example for Bach over Schoenberg, and that these preferences differ by individuals.  In addition, the bird owners I have been in touch with often claim that their birds prefer or only respond to certain songs or certain types of music.  So I would not be surprised if these birds did have individual musical preferences in a sense similar to humans'. This is a very interesting topic for future work.

JV- I was surprised to read that birds do not entrain (move in sync with) auditory beats in their natural behavioral repertoire. But don't they exhibit closely related behaviors, such as moving rhythmically without music to communicate with each other, producing songs, and copying each others movements? And don't some animals even produce meaningful rhythms on objects by tapping on them? I guess no scientist, however, has ever documented a non-human moving in time to songs produced by another non-human?

AS- Exactly! Animals do all of these related things, but to our knowledge they never actually entrain in the wild.  In order to entrain, they would have to hear a periodic sound from an external source, and line up their movements with this sound in time.  

JV- If entrainment is just a by-product of selection for vocal mimicry, why do you think it's so important for humans, even possibly becoming a sexually selected for ability (since the best human dancers usually have no trouble securing partners on and off the dance floor)?

AS- This is a great question and requires a bit of a nuanced discussion.

Although we think entrainment emerged at least partially as a byproduct of selection vocal mimicry, it's not clear that entrainment is just a by-product. This is because there are lots of cognitive mechanisms that all have to be in place before something like entrainment can happen. Our data support the idea that selection for vocal mimicry gave us something in the brain that was necessary for entrainment. But it may be that after that machinery was in place, further selection and other cognitive machinery was needed too.  So it is possible that some of the cognitive machinery needed for entrainment emerged as a byproduct, while other parts (in humans at least) emerged through direct selection.

In addition, even if entrainment originally emerged entirely as a by-product, that does not necessarily mean that it would not have some value or effect once it did exist.  It could be that even before dance, our human ancestors had a latent perceptual preference for accurate synchrony. If this were the case, once we had the ability to keep a beat and expressed it in dance, good dancers might be preferred.  We've seen things like this in animal behavior before, so it wouldn't be unheard of!

JV- What else would you like us to share with others about your latest work?

AS- You could mention how we ruled out various alternate explanations of this dancing phenomenon.  (Are the birds really dancing to the beat, or are they cheating in some way?)

For instance, we know the birds aren't simply following visual motion, because in our experimental sessions we made sure that there were no rhythmic visual stimuli and made sure the humans were still.  We also made sure that the birds couldn't have been specifically trained to respond in a specific way to one certain song by playing new songs that we constructed ourselves, and using music with various tempos.

We also went to great lengths to make sure that the actual movements the birds were producing were actually lined up with the musical beats, and were lined up well enough that we can be confident they didn't just happen by chance.  These types of analyses let us be sure that this is not just some sort of "Clever Hans" phenomenon, where an animal looks really humanlike but in reality is cheating in some way.  It really looks like these birds have a very humanlike capacity to hear a musical beat and synchronize their movements along with it.

Photos of Snowball dancing courtesy of owner Irena Schulz, founder and president of the Bird Lovers Only Rescue Service, Inc.