Although children learning to speak may be a beautiful experience in the home, it inspires hot debate among psychologists studying it. Scientifically, babble is described as a “repetitive activity in which mandibular depressions alternate with elevations that briefly narrow the vocal tract, the specific points of obstruction being determined by the tongue and the lips” (Locke 1995). In other words, babbling is making sounds like “bababa”. However, scientists are still not entirely sure why we babble. Psychologists studying the phenomenon of babble have staked out two main positions in explaining the phenomenon.
The first group, the “motorists” as I shall call them, attributes this special ability to recently developed motor control of the mouth. The motorist hypothesis posits that babbling is a left brain activity, controlled by developing motor skills that the new infant is testing out. Most significantly, this theory understands language to be a coincidental outgrowth of babble rather than present throughout the babble-to-language maturation (Petitto 2004).
The other group, the “babblinguists” as I shall happily name them, takes an almost polar opposite view. The babblinguists understand babble to be a fundamentally lingual activity: controlled by the right side of the brain, communicative in intent. They believe that babbling is a tool for babies to use to figure out all the syllables of their home language. This is in contrast to the motorist theory, which states that babbling is simply basic motor exploration: to babblinguists, babbling is for a targeted purpose, and that purpose is language (Petitto 2004).
Speech development begins at birth, where psychologists classify the babies cry as the first stage of prespeech development. About 7 weeks in, the baby will begin to coo, which is characterized by an attachment to contentedness, and singular long vowels. The next stage is that of “vocal play” which happens after about 16 weeks. In this stage, infants start using consonant-like sounds, and putting them together with vowel like sounds. This is sometimes called “marginal babbling.” The next stage, though, is the stage that inspires all the passion and fury. Between 6 and 9 months, babies engage in reduplicated babbling, or canonical babbling. A major group of study within this debate – deaf children – comes into play at this stage. This is the first stage when deaf children and hearing children differ in their vocalizations. This makes them ideal for studying to determine what stimuli from their own voice or others’ voices are necessary to facilitate babbling. In studying sign language, it presents perhaps an understanding of the purpose of babble (Hoff, 2005). Thus the 6 to 9 month group is the group of interest for psychologists studying the possibility of infant lingual abilities.
Each side of the debate has a number of ways to prove their hypotheses, from neural to behavioral data. John Locke et al. attempted to prove linguistic basis for babbling in a behavioral study in 1995. He gathered 61 infants at various stages of babble ability: pre-babbler, new babbler, or experienced babbler. He placed the infant on its mother’s lap and presented it with a rattle to grab immediately in front of it. Because language is a left brain activity, its development, unlike the development of motor skills in general, should correspond with an overuse of the right hand specifically during the lingual-developmental stage of infancy. Locke indeed found what he was looking for: that around the time of learning to babble in infants, they will be more likely to use their right hands to shake the rattle, and to do so more often. Thus he concluded his test as a success (Locke, 1995). The babblinguists had, for the moment, won.
A few years later, though, some researchers found some problems with his study. Locke et al. hadn’t followed up on which children would eventually become left or right handed so he didn’t have back data to compare his results to. More importantly, his classification of children was flawed. The only pieces of information he had about the children were their ages and whether they babbled or not: not how long they had been babbling. Without this information, his found increase in right hand activity could just be a function of age, rather than babbling stage. Because of these flaws, Iverson et al. decided to conduct a new study exactly as Locke would have intended, just with flaws fixed (Iverson, 2006).
This new study used 26 infants and concentrated a bit more on specifics than Locke did. They targeted their age samples around the developmental stage where Locke had noticed the most distinct differences in rattle shaking. Furthermore, they noted not simply rattle shaking, but divided activities into reach, grasps, and shakes including duration. Researchers watched children as they sat on laps, or played in their homes. Also, advanced video techniques were used to more accurately gauge infant movement and patterns (Iverson, 2006).
Despite all these safe steps taken, or perhaps because of them, Iverson et al. were unable to reproduce the results of Locke et al. They found no right hand preferential specifically around the time of babble development. Thus, they concluded that Locke’s study should not be used as support for the hypothesis that babbling is a left-brained activity and thus lingual (Iverson, 2006).
Another false hope for the linguist view came when Petitto and Marentette conducted an experiment on deaf children and hand motions. Because deaf, or severely hearing impaired children do not experience sound in the same way most do, they do not babble in the same way most do. In fact, it seems that the auto-auditory response is necessary in the development of babble. Without being able to hear themselves produce sound, these infants have a significantly more difficult time producing the basic babble sounds like “dadada” (Koopmans-van Beinum).
Petito et al. hypothesized that despite this lack of coordination of the vocal tract, if babble is language bound, it will come out in some other form. This form was sign language. They found that although these deaf babies do not babble audibly, their hand motions create parallels which demonstrate a universal maturation of the language facilities – even in deaf children. Their sign-babble resembled babble in spoken language in that it was quick repeats of one unit of language, and shadows of real parts of the language (Petito, 1991). It seemed for a little that the debate had been closed.
Several years later, R. P. Meier conducted a similar study and found not only that deaf children were babbling with their hands, but that hearing children were similarly babbling with their hands. This turned Petitto’s findings on its head: Deaf babbling was no longer a lingual yearning trying to get out, rather, a strictly physical repeated exercise of muscles. The flag would be back on the motorists’ side (Petitto 2004).
But Petitto responded to her criticisms with another experiment. In this experiment she attempted to demonstrate authoritatively that the difference between deaf-babble and hearing-babble is significant. She studied a group of babies exposed to sign language, and another exposed to audible language. In this study both groups were hearing. This way, if hearing is indeed necessary for the development of proto-language, all of these babies – sign group included, will have the opportunity to develop audible babbling. The difference is that these hearing babies can hear themselves but get no reinforcement for using audible babbling as a form of communication.
She took six infants, three learning English, English, and French, and three learning sign language in American, American, and Langue des Signes Québecoise. Petitto used Optotrak technology to digitally trace the arm movements of each of the babies. She and her team placed four LEDs on each of the children’s hands and watched them in a car seat as they played and responded to stimuli. The Optotrak scans yielded an interesting result: both groups of babies were similarly active in hand waving, but the hearing babies exposed to sign language produced lower frequency hand motion than hearing babies exposed to verbal language. Petitto understood this lower frequency to be characteristic of babbling, and indeed, when video tapes were later watched, those low-frequency instances were also vestiges of signed language. It seems that these babies are trying to recreate what they are seeing in a means to communicate (Petitto, 2004).
There are many ways to try to answer this debate. Testing handedness is one technique. The deaf/hearing dichotomy is another. Psychologists continue to look at the problem from different angles to distil down a distinct answer, but different angles keep yielding different results. All these studies indicate how difficult it is to find absolute data in resolving the debate between the motorists and the babblinguists. Perhaps by the nature of the specimen or the complexity of the brain, the babble debate is still baffling the scientific community.
Works Cited
Petitto, Laura Ann; Holowka, Siobhan; Sergio, Lauren E; Levy, Bronna; Ostry, David J. (2004). Baby hands that move to the rhythm of language: Hearing babies acquiring sign languages babble silently on the hands. Cognition, 93(1), 43-73.
Koopmans-van Beinum, Florien J; Clement, Chris J; van den Dikkenberg-Pot, Ineke. (2001). Babbling and the lack of auditory speech perception: A matter of coordination? Developmental Science, 4(1), 61-70.
Locke, John L; Bekken, Kaaren E; McMinn-Larson, Laura; Wein, Debra. (1995). Emergent control of manual and vocal-motor activity in relation to the development of speech. Brain and Language, 51(3), 498-508.
Iverson, John L; Halla, Amanda J; Nickela, Lindsay; Wozniak, Robert H. (2006). The relationship between reduplicated babble onset and laterality biases in infant rhythmic arm movements. Brain and Language, (In press, corrected proof).
Petitto, L.A.; Marentette, P.F., (1991) Babbling in the manual mode: evidence for the ontogeny of language. Science, 251, 1483-1496.
Hoff, E. (2005). Language Development (3rd ed.). Belmont, CA: Thomson Wadsworth.
