Bababa, dadada and mama are all happy to hear their baby's babble. Babbling is the first step in learning to talk. Babbling is a common characteristic of infants, regardless of the language they are learning.
Speech is the oral output of language. To produce one of the basic speech subunits, the syllables, you need to control your lips, tongue and jaw.
Babbling has many universal characteristics, such as repetition of syllables or use of rhythm. Babbling allows infants to practice their vocal skills and learn to produce the correct syllables.
Language is the most important thing about human nature. Scientists have been trying to understand its evolutionary roots for decades. It is promising to uncover key features of human speech by studying the biological basis of language across species, as I did in bats.
I am a behavioral biologist and have spent months recording the vocalizations of bat colonies in Costa Rica and Panama for 10 hours.
There are striking similarities between the babbling of these bat pups, and that of human infants, according to my colleagues. It may be possible to understand vocal learning's cognitive and neuromolecular bases by identifying a mammal with a brain structure similar to human beings.
Vocal learning in animals
Songbirds have allowed scientists to learn a lot about vocal imitation and development. They are one of the most well-known vocal learners. The learning process of young male songbirds is interestingly similar to human speech development.
The practice phase is similar to human infant babbling and it's used by young male songbirds.
Songbirds and humans have different vocal apparatus. While songbirds use a syrinx to vocalize, people use a larynx. Their brain architecture is also different. It is difficult to draw direct conclusions about songbird research for humans.
Fortunately, in Central America's jungle, there is a mammal who engages in a conspicuous vocal practice behavior strongly reminiscent human infant babbling. It's the neotropical greater Sac-winged bat Saccopteryx Bilineata.
This small bat's pups are dark-furred and have two distinct white wavy stripes at the back. They engage in daily babbling behavior throughout their entire development.
Greater sac-winged bats have a wide vocal repertoire, which includes 25 different syllable types. A syllable, which is the smallest unit of acoustic sound, can be defined as a sound that is surrounded by silence.
Adult bats can sing two songs and have multisyllabic vocalizations. The territorial song alerts potential rivals that their owner is prepared to defend their turf, while the courtship sing lets female bats know if a male bat is a good choice for a mate.
My colleagues and I are particularly interested in the vocal imitation ability of the greater sac-winged Bat. This is the ability to create a new sound by ear from scratch. It needs acoustic input. This is similar to human parents talking with their infants or, in the case the greater sac-winged, adult males singing.
Scientists have not found any other mammal non-human that can babble, except for the pygmy marset, which is a small South American primate that cannot imitate vocal sounds.
The first opportunity to examine pup babbling in detail in a species capable of imitating the vocalizations was offered by the greater sac-winged bat
How similar is bat babbling with human infant babbling, you ask?
Bat babbling can be enjoyed for hundreds of hours
I monitored the vocal development in eight colonies of wild pups to answer this question. S. bilineata seek shelter and protection from the outside walls and tree crevices during the day. They are very light-tolerant and prefer to be several centimeters from each other. This makes it easier to record and observe particular individuals.
I used colored plastic bands to mark their forearms so that they could be identified. From birth to weaning, I tracked 20 pups.
Between sunrise and sunset, the pups talk between 2.5 and 10 weeks of age. The noise is very loud and audible to the human ear. Some of the syllables are within our range of hearing, while others are too high to hear.
I recorded the babbling of each pup and their accompanying behaviors throughout development. Some of these lasted up to 43 minutes. Adult bats, however, produce vocalizations that only last a few seconds.
Scientists know for a long time that puppies learn to sing when they mimic adult tutors vocally while babbling.
Our new study shows that infants' babbling shares many of the same characteristics as human babies: rhythm use, duplication of sounds, and early onset of the babbling stage during development.
As infants make sounds that can be recognized as "canonical adult" syllables, bat pups' babbling is made up of precursors to adult vocal repertoire.
Just as human babbling can include sounds that the infant makes when exploring their voice, bats can also produce protosyllables.
Puppy babbling is also universal. Every pup, regardless of its sex or regional origin, babbled throughout its development.
Talking baby from mom to puppy
My first field season was marked by a change in the behavior and vocalization of mothers and their pups during babble sequences. While babbling, mothers made a distinctive call to their pups.
Humans can alter the way they speak depending on whether they are speaking to infants or adults. Motherese, also known as infant-directed speech, is a special type of social feedback for vocalizing infants. It has universal characteristics, such as a higher pitch, slower pace, and an exaggerated intonation contours.
When people speak "motherese", the timbre of their voice changes, as does when they talk to adults. Timbre refers to the sound of a voice making it sound either cold and harsh, or warm and cozy. It is possible that female bats could also change their timbre depending on who they are calling.
We were able to see that a non-human mammal could change the color of its voice depending on who it was addressed to. Bats can also use baby talk!
The results of our study show that the greater sac-winged Bat is a promising candidate to be used for cross-species comparisons on the evolution of human speech. Babbling can be compared to a behavioral reading of vocal learning occurring in the brain.
The pups mimic adult singing and can be heard babbling. This gives us insight into when learning is occurring. This gives us the unique opportunity to examine the genes involved in vocal imitation.
Because bats have the same basic brain architecture as humans, our research can be translated from bats to people. It is amazing to me that these mammal species are so similar in their pursuit of the same goal, which is to acquire complex adult vocal repertoires and language.
Ahana Aurora Fernandez is a Postdoctoral Researcher in Behavioral Ecology and Bioacoustics at Museum fr Naturkunde, Berlin
This article was republished by The Conversation under Creative Commons. You can read the original article.
