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Babbling is a stage in child development and a state in language acquisition, during which an infant appears to be experimenting with uttering articulate sounds, but does not yet produce any recognizable words. Babbling begins shortly after birth and progresses through several stages as the infant's repertoire expands and vocalizations become more speech-like. Infants begin to produce recognizable words usually when they are around 12 months of age, though babbling may continue for some time afterward.
Babbling is a state in language acquisition. These vocalizations do not 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 they are 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 infants are 6 months old they 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, it displays 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 it 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 complexity of the sounds that infants produce makes them difficult to categorize, but the above rules tend to hold true regardless of the language to which children are exposed.
The transition from babbling to language
Two hypotheses have been devised in order to explain how babbling is related to language development.
- The Continuity Hypothesis - According to this hypothesis, 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 babbling" 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 is 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 for the sounds that they are making. This reinforcement through feedback helps infants to focus their attention on 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 altogether 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 are conflicting perspectives to which of these hypotheses are more relevant, 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. The ordering of consonants and vowels in the babbling of English, French, Swedish and Japanese infants also appears to resemble that of their native language. These findings support another hypothesis, the “babbling drift hypothesis” in which infant babbling resembles the phonetic characteristics of a child's native language through exposure to speech. When babies are exposed to two languages, they normally babble in the language that they are most exposed to. The dominant language is considered to be the one that children have the most exposure to. Most often infants do not produce a blend of languages while babbling however, may switch between languages. Sometimes infants 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 its 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. The larynx or voicebox, originally high in the throat to let the baby breathe while swallowing, descends during the first year of life, allowing the pharynx to develop and facilitating the production of adult-like speech sounds.
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 lowered, 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
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. Babbling should appear at the same age and in similar forms in hearing and deaf child, however, further continuation of babbling and speech development depends upon the ability for the child to hear themselves. For this reason, deaf children stop babbling vocally earlier than hearing children, and therefore have great difficulty learning to speak. 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. This suggests that experience with auditory speech is necessary in language development. Some researchers have taken these findings as evidence against the hypothesis that language is an innate human capability.
Exceptions exist for infants with some 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 they will never speak at all.
A number of solutions have been used for hearing impaired humans to gain auditory experience. One of which is hearing aids; they can be used to help infants reach babbling stages earlier. Cochlear implants have also been tested. Once the surgical implantation is complete, an infant has the opportunity to experience language. Once language has been heard, the infant begins to babble and speak in rhythmic patterns just as normal hearing infants do.
Deaf babbling is now titled manual babbling, and is structurally identical to vocal babbling in its development. 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 in the same stage of development, but deaf infants do not begin manual babbling until they are at least 10 months old. There are three main components of 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 aspects of vocal babbling.
Although all babies imitate with their hands the movements that they see before their eyes, deaf infants begin to make gestures that are distinct from all other hand movements and gestures. Typical gestures for example are raising arms to be lifted up, or grabbing/reaching to indicate wanting a bottle; these are used referentially with no organization, principal or combinatorial units. 
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.[6}
Children are able to produce 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. It is difficult to study manual babbling as often then manual activity can be mistaken as gestures rather than signs. When deaf children are in fact babbling it will most often take place in front of their torso in a designated American Sign Language call the phonetic space. One of the most common signs of manual babbling is the extension and spreading of all fingers. This sign is also one of the first signs an infant will make in manual communication.
If a hearing infant has deaf parents, it will still imitate the signs that it sees its 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.
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. 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 varieties of immature songs that are referred to as babbling because the immature songs precede those that are fully developed. As with humans, if these songs 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 as feedback, 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.
The physiology of the animal is important. The properties of the ear and vocal tract, as well as the brain regions used in analyzing and processing information are critical determinants of 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 nevertheless contains 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 is able to form before the period where learning to sing occurs. Social interaction is important in vocal learning where non-singing females can even influence an infant through feedback.
Pygmy marmoset (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 by a pygmy marmoset contains approximately 10 different call types. This variety of call forms produced by this creature is comparable to babbling in human infants for a number of reasons. Like reduplicative babbling in humans, the call is often repeated several times before a new sequence of sounds is produced. The vocalizations gain attention from caregivers and provide practice for future vocal behavior. For these reasons, pygmy marmoset calls are seen 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, social interaction or during times of alarm. As human infants have, 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 practising 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 researched until recently in non-primate mammals. The sac-winged bat (Saccopteryx bilineata) is a social creature and the vocalizations that it produces 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.
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