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Babbling (also called twaddling) is a stage in child development and a state in language acquisition, during which an infant appears to be experimenting with uttering sounds of language, but not yet producing any recognizable words. (Crucially, the larynx or voicebox, originally high in the throat to let the baby breathe while swallowing, descends during the first year of life, allowing a pharynx to develop and all the sounds of human speech to be formed.) Babbling begins at approximately 5 to 7 months of age, when a baby's noises begin to sound like phonemes. Infants begin to produce recognizable words usually around 12 months, though babbling may continue for some time afterward.
In humans 
Babbling is the first sign of human language. These vocalizations do not generally contain meaning or refer to anything specific. Human infants are not excited or upset when babbling, but instead they will babble spontaneously and incessantly only when emotionally calm.
The sounds and expressions of babbling are produced before an infant begins to construct recognizable words. This is mainly due to the immaturity of the vocal tract and neuromusculature at this age in life.
Infants first begin vocalizing by crying, followed by cooing and then vocal play. These first forms of sound production are the easiest for children to use.
When reaching an age of 6 months, infants are finally able to control the opening and closing of the vocal tract, and upon obtaining this ability, infants begin to distinguish between the different sounds of vowels and consonants. This period is known as the beginning of the canonical stage. During the canonical stage, the babbling involves reduplicated sounds containing alternations of vowels and consonants (e.g.; baba or bobo).
By the time an infant reaches 8–9 months, they display productions of more advanced sounds known as variegated babbling. Variegated babbling differs greatly from reduplicated babbling. This stage includes more complex combinations of consonant and vowel syllables (e.g.; babadoobe).
By 9–10 months of age, infant babbling begins to resemble the native language of a child. The final stage is known as conversational babbling, or the "jargon stage" (usually occurring by about ten months of age). The jargon stage is defined as "pre-linguistic vocalizations in which infants use adult-like stress and intonation". The general structure of the syllables that they are producing is very closely related to the sounds of their native language and this form of babbling significantly predicts the form of early words.
Infants continue to use intonation patterns and timing that matches the characteristics of their language. Most babbling consists of a small number of sounds, which suggests the child is preparing the basic sounds necessary to speak the language to which he is exposed.
If babbling occurs during the first year of life, it can typically be concluded that the child is developing speech normally. As the baby grows and changes, his/her vocalizations change as well. Babies use these vocalizations to communicate. They commence vocal development by crying, progress to loud yelling noises, and finally make speech.
There are two types of babbling. Reduplicated babbling consists of repeated syllables consisting of a consonant and a vowel, such as "da da da da" or "ma ma ma ma", whereas variegated, or non-reduplicated babbling consists of a mix of syllables, such as "ka-da-bu-ba-mi-doy-doy-doy".
The consonants that babbling infants produce tend to be any of the following : /p, b, t, m, d, n, k, ɡ, s, h, w, j/. The following consonants tend to be infrequently produced during phonological development : /f, v, θ, ð, ʃ, tʃ, dʒ, l, r, ŋ/. The complex nature of sounds that developing children produce make them difficult to categorize, but the above rules tend to hold true regardless of the language to which children are exposed.
Link between babbling and language 
Two hypotheses have been devised in order to explain how babbling is related to language development.
- The Continuity Hypothesis - According to these claims, babbling is a direct forerunner to language. At first, infants produce universal sounds that exist in all areas of the world and in all languages. "Reduplicated canonical bablling" produces a number of sounds but only some of them ("ma ma" and "da da", turning into "mommy" and "daddy", respectively) are recognized as meaningful and thus reinforced by caregivers and parents, while the others are abandoned as meaningless (this is the argument in, for instance, Susanne Langer's Philosophy in a New Key). This hypothesis agrees with the claim that the anatomical changes of the vocal tract are very important, but suggests that the social environment in which an infant is raised has a greater influence on the development of language. Infants pay close attention to their caregivers' reactions and use their feedback as approval to the sounds that they are making. This reinforcement through feedback helps infants to focus their attention on very specific features of sound. Social feedback facilitates faster learning and earlier production of a variety of advanced words.
- The Discontinuity Hypothesis - This alternative idea suggests that babbling has absolutely no relationship to language development. According to this hypothesis, infants produce sounds in no particular order and as they grow, they may drop certain sounds only to pick them up again in later months. This is a giant step backwards and as infants grow, they may incorrectly and inconsistently use sounds that they had already conquered in the early babbling stages. Sometimes, they lose them all together before learning how to speak. Over time, infants will relearn sounds and develop words in a specific language. The hypothesis also implies that when children finally reach the age where they are able to learn their native language, they develop phonological sounds in an orderly manner. There can be a period of silence between productions of babbling and productions of the first words in speech.
There is no clear evidence for either of these hypotheses, leaving them both as possibilities for connections between the speech stages in life.
As suggested in the continuity hypothesis, there is some evidence that babbling varies depending on the linguistic environment in which a baby is raised. For example, it has been noted that infants raised in French speaking environments display greater amounts of rising intonation in comparison to infants raised in English speaking environments. This is due to the differences between French and English intonations while speaking. By comparing infants in English, French, Swedish and Japanese linguistic backgrounds, babbling reveals that placement of consonants and vowels also resembles native languages. These findings support another hypothesis; the “babbling drift hypothesis” in which infant babbling resembles the phonetic characteristics of their native language through exposure to speech. When infants are exposed to two languages after birth, they typically babble in their dominant language. The dominant language is considered to be the one that children have the most exposure to. Infants do not produce a blend of languages while babbling and sometimes they may choose which language they prefer to babble in based upon particular features.
A human mouth moves in distinct ways during speech production. The International Phonetic Alphabet was formed in 1897 as a representation of the sounds produced by language. When saying each individual sound out loud, it is noticeable that a human uses different parts of their mouth, as well as different methods to differentiate particular sounds. During the beginnings of babbling, infants tend to have greater mouth openings on the right side. This finding suggests that babbling is controlled by the left hemisphere of the brain.
Reduplicated babbling (such as bababa) involves a rhythmic opening and closing of the jaw. According to the Frame Dominance Theory, when the mandible (jaw) is elevated, a consonant sound will be produced. When the mandible is depressed, a vowel like sound is produced. Therefore, during a reduplicated sequence of sounds, the consonant and vowels are alternated as the mandible elevates and depresses. The opening and closing of the mouth alone will not produce babbling. Phonation is necessary during the entire movement in order to create a meaningful sound. Other important body parts involved in articulation, such as the tongue, lips and teeth remain in a stable resting position during babbling. However; the position of the tongue is not always controlled during the open and close cycle of the mouth. Also, sound is not constantly produced throughout these cycles of mouth movements. Sometimes during the babbling period, the motions can be made without any vocalization at all. Deaf infants produce manual babbling through similar rhythmic alternations, but they perform with their hands instead of their mouths. As a baby begins to produce sounds beyond the reduplicated sequences of babbling, they exhibit equal sized mouth or hand openings on the right and left sides.
Children who cannot babble for some physiological reason, such as having a breathing tube in their throat, do subsequently acquire normal pronunciation but their speech development is significantly delayed.
In deaf infants 
Vocal babbling 
It has been moderately challenging to study deaf infants in the past because it is uncommon to diagnose hearing disabilities within the first year of a child’s life. It is also difficult to locate deaf infants that have had severely impaired hearing since birth, have been diagnosed within the first year of their lives, and do not suffer from any other impairments.
Research has been conducted to determine whether or not infants with impaired hearing can demonstrate typical vocal sounds. Infants who are deaf do show signs of vocal babbling, but in minimal amounts. This suggests that early babbling arises from inherent human tendencies to use the vocable articulators in particular ways during early language acquisition. Babbling of any language should appear if the child is exposed to a source of communication, but babbling can be delayed or non-existent for deaf children. However, contradictory evidence supports that language will not develop fully without auditory experience. Therefore, deaf children are not only significantly delayed in language development in comparison to their speaking counterparts, but they also produce fewer noises. Due to the findings relating to this babbling delay, researchers have rejected the belief that language is an innate capability that humans have. Researchers instead support the suggestion that experience with auditory speech is necessary in language development.
There are exceptions to these studies on the occasion that infants are not completely impaired of all hearing. Children with varying degrees of hearing loss display different speech signals and babbling. Those with more severe hearing loss have less experience with auditory communication and therefore show worse canonical babbling and language production. Some deaf infants will never reach the canonical stage of babbling, thus never speaking at all.
In order for hearing impaired humans to gain auditory experience, a number of solutions have been implemented. Hearing aids can be used to help infants reach babbling stages earlier. Cochlear implants have also been tested. Once the surgical implantation is complete, an infant begins to listen and have experience with language outputs. As soon as language has been heard, they begin to babble and speak in rhythmic patterns just as normal hearing infants do.
Manual babbling 
Although all infants move their hands in imitation to what is modeled in their environment, around 9–12 months deaf infants begin to produce gestures that are distinct from all other hand movements. This was originally thought to represent the first indicators of sign language. Just as hearing infants babble with their mouths, deaf infants babble with their hands. Deaf children acquire signs for the same concepts that are present in English speaking children, but deaf infants do not reach this stage of babbling until 10 months or later. Children are able to produce manual articulation of words correctly, which is important since many articulation tendencies of manual babbling transfer to the children’s early sign production and then later into the production of words.
Interestingly enough, if a hearing infant has deaf parents, they will still imitate the signs that they see their parents displaying. This is evidence that manual and vocal babbling is possible in both hearing and deaf infants. If infants are exposed to sign language, regardless of whether they themselves are deaf or hearing, they will babble with their hands at approximately the same time vocal babbling appears. Sign production appears a few months before word production generally does in hearing children.
After it was established that deaf infants could babble through other means than their mouths, the patterns in which productions occurred were studied. Hearing and speaking infants follow identical maturational paths in language acquisition. Both go through a number of stages, and exhibit similar complexity in their babbling sequences. In studies where deaf and hearing children were compared, deaf children produced more multi-movement manual babbling than children with their hearing.
Deaf babbling is now titled manual babbling, and is structurally identical to vocal babbling in its development. The most common sign in manual babbling is where all fingers are extended and spread and it is also related to the first signs an infant will make. There are three main components to manual babbling. The hand gestures contain a restricted set of phonetic units, a syllabic organization and are used without reference or meaning. This is comparable to the important aspects of vocal babblings.
In nonhumans 
Not only are songbird and human language parallel regarding neural and molecular factors, they also are similar in how their communication is initially produced. Observations about these similarities can be traced back to Charles Darwin and his studies. Avian and mammalian brains are similar in form and connectivity and there may even be a gene that is relevant to speech found in both organisms. The learning of a song is produced through a mix of interaction, experience, and predisposition as shown when young songbirds will imitate their species call when presented with songs from their own and another species. They are physically capable of producing either song, but do not. Humans learn language through similar means, which is why this early vocalization in songbirds is considered babbling.
Young male songbirds produce a variety of immature songs that often are referred to as babbling because the immaturity precedes the fully developed mature song. As with humans, if these sounds are reinforced with positive social feedback, they are more likely to recur. Since the females do not sing songs, they are in charge of providing the feedback. If females provide more social signals, males will develop more mature songs at a faster rate than other male birds. Young birds require reinforcement from adults in order to finalize their songs. Another relation to human infants, is that the amount of vocalizations is not key, but rather the quality of the sounds that is retained and resembles the final produce of language.
Another important factor is the physiology of the animal where brain regions used in analyzing and processing information and the properties of the ear and vocal tract are critical determinants to how song is interpreted and later produced. In studies using isolated birds that have not had exposure to song, they produce an abnormal ‘isolate song’ that still retains species-specific aspects. This shows that the neural pathways have predetermined features that allow for such a phenomenon to occur. The pathways are able to allow for plasticity of the songs that can be learned in the future.
There is an important phase in development when song learning is best accomplished. This phase is called the ‘sensitive period’ and the amount of change that a songbird experiences in adulthood varies by species. Young birds have a production phase after a listening phase of development. The production of song is called ‘subsong’ where vocalizations resemble that of an adult as time passes. Memory for songs are able to form before the period where learning to sing occurs. Social interaction is important when dealing with vocal learning where non-singing females can even influence an infant through feedback.
Pygmy marmosets (Cebuella pygmaea) 
Pygmy marmosets have been studied and found to produce complex vocalizations 2–3 weeks after birth. Both sexes are capable of creating calls at a rate of 3 calls/second and each bout of calls can last up to 6 or 7 minutes. A normal series of calls for a pygmy marmoset contains approximately 10 different call types. This abundance of call forms produced by this creature is comparable to babbling in human infants for a multitude of reasons. Like reduplicative babbling in humans, the call type is often repeated several times before a new sequence of sounds is produced. The vocalizations also gain attention from caregivers and provide practice for future vocal behavior. For these reasons, pygmy marmoset calls are also distinguished as babbling behavior.
There are a total of 16 call types in pygmy marmoset babbling language. Different calls serve different survival functions such as when desiring food and social interaction or during times of alarm. As human infants do, marmoset babies have higher rates of social interaction when producing babbling sounds. During the juvenile age, marmosets often regress back to babbling stages if a new infant is born. It is suggested that their production of babbling calls increases because they are seeking attention and social interaction. Another babbling occurrence during the juvenile age is the addition of territorial calls and mild threat vocalizations. Although babbling is important for practicing adult calls during the juvenile age, babbling decreases with age in pygmy marmosets. Overall, babbling progresses through a series of stages from infancy to adulthood and slowly leads to the construction of adult calls.
Sac-winged bat (Saccopteryx bilineata) 
Babbling-like behavior in songbirds, humans and some nonhuman primates has been previously researched, but it has not been seen until recently in non-primate mammals. The sac-winged bat (Saccopteryx bilineata) is a social creature and the vocalizations that they produce depend on the social situation that the animal is in. This bat has a large repertoire of vocalizations with males being more vocal than females. Echolocation pulses, barks, chatters, and screeches are used in various social situations including courtship and territorial defense. Infants produce isolation calls if their mothers are absent, but the pups also produce vocalizations that mirror those of adults. Both sexes of infants babble, even though as an adult, the vocalizations are solely produced by males. Social context, mothers, and surrounding bats do not influence pups because the multiple vocalizations are combined regardless of the situation. Since there is not a social aspect correlated with the vocalizations, the productions of the sounds suggest that the pups vocalize for training. The pups repeat and combine adult vocalizations so that they resemble babbling in what humans, other primates and some songbirds do as infants. However, while human babbling increases social interactions, there are no social responses to babbling in bats. Babbling is common in infants that have a large repertoire of adult vocalizations to learn and this is seen in the pups of Sac-Winged bat.
See also 
- Naomi S. Baron, Growing up with Language: How Children Learn to Talk (Reading, MA: Addison-Wesley, 1992), p. 41-43, ISBN 0-201-55080-6
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- Sroufe, Cooper, & Dehart, 1996, p. 258
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- Waldron, Sharn (2007). "The Significance of the Emergence of Language and Symbol in the Development of the Young Infant". Journal of Religion and Health 46 (1): 85–98.
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- Schauwers, Karen; Paul J Govaerts, Steven Gillis (2008). "Co-occurrence patterns in the babbling of children with a cochlear implant.". The syllable in speech production.: 187–204.
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- Bass-Ringdahl, Sandie M. (2010). "The Relationship of Audibility and the Development of Canonical Babbling in Young Children With Hearing Impairment". Journal of Deaf Studies and Deaf Education 15: 287–310. doi:10.1093/deafed/enq013.
- Bolhuis, J. J.; Okanoya, K., & Scharff, C. (2010). "Twitter evolution: Converging mechanisms in birdsong and human speech". Nature Reviews Neuroscience 11: 747–759. doi:10.1038/nrn2931.
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- Knornschild, M.; Behr, O. & Von Helversen, O. (2006). "Babbling behavior in the sac-winged bat (Saccopteryx bilineata)". Naturwissenschaften 93: 451–454. doi:10.1007/s00114-006-0127-9. PMID 16736178.