The Role of Nervous System Architecture in Language Acquisition
It is a known fact that infants learn language with remarkable speed, but how they do it remains a mystery. Recent research proves that these infants and younger children's brains are better equipped to learning new languages than adults are. I plan to investigate the observations and evidence related to this assertion, by connecting the arguments to the new neurobiological frameworks such as the I-function and central pattern generation (CPG). I would like to use these two frameworks to explain the phenomena of children being better language learners than adults.
Corollary discharge signals are described as a group of neurons communicating with a second group of neurons. This interaction is associated with coordinated movement like central pattern generation (CPG). Some examples of coordinated movement are like walking, dancing, typing, etc. For this paper I would expand the definition of CPG to include the acts of speaking and learning a new language.
The corollary discharge is a component of the central pattern generator. CPGs are neural pathways that the I-function has certain control over. Based on these set of observations when adults learn a new language a new neural pathway (CPG) is paved. However in order for adults to speak fluently in this new language they must 'think' in this language. The ability to 'think' in the new language can only be accomplished by overriding the I-function and reverting from the English default CPG to the Spanish new CPG. This process is what accounts for the lack of fluency. Since the I-function is not completely inactivated adult students think of Spanish in English before formulating sentences. Since babies may have inactive I-functions they do not have to override anything but rather directly switch to a different language naturally.
Dr. Patricia K. Kuhl's recent neuropsychological and brain imaging work indicates that language acquisition involves neural commitment (1). The concept of neural commitment can be related to what we have learned as the CPG. The concept of neural commitment involves the initial coding of native-language patterns, which eventually clash, with the learning of new patterns (such as those of a foreign language (1). The I-function regulates the formulation of CPGs and how these certain patterns play out. The I-function intervenes with any patterns (CPGs) that do not conform to what Kuhl calls a 'mental filter'.
Thus early learning promotes future learning that conforms to and builds on the patterns already learned but limits future learning of patterns that do not conform to those already learned. So supposedly a child that speaks fluent Spanish may not experience much difficulty learning French as a second or third language. This is because the existing Spanish oriented CPGs may overlap or have some similarities with the newly paved French CPGs. However the same child may experience difficulty learning a language with a different structure from Spanish-such as Arabic or Russian (2).
Using MRI and animation technology to study the brains of children, researchers like Dr. Paul Thompson of UCLA have discovered that children are processing language information in a different region of the brain than adults. When children acquire language, this same part of the brain, called the "deep motor area," is what they use. Adults store information in a more active brain region. As a consequence, adults usually think sentences through in a native tongue and then translate them in the new language, instead of thinking automatically in another language like a child would (3).
This MRI technology based evidence supports that the 'deep motor area' represents an inactive I-function in the babies that are able to learn languages directly and naturally. In the case of the adults the more active regions of the brain represent the presence of the intervening I-function which can account for the adult students consciously learning and speaking a new language, and constant return to their native language. This reverting back tedious process account for the lack of fluency and time for language acquisition in adult students, as they consciously have to switch the CPG to the different neural pathways.
Based on Dr. Paul Thompson's findings when babies learn new languages their respective I-functions are deactivated and thus they are capable of forming new pathways and smoothly transitioning from one to the other without any intervention on the part of the I-function. Evidence from Dr. Kuhl also supports the above findings. Evidence from magnetoencephalography (MEG) shows that while adults are processing foreign-language speech sounds a larger area of the brain is activated for a longer time period than when processing native-language sounds-this indicates that the I-function is active and slowing down the new language learning process for adults (2).
For adults and teenagers who already know a language like English they experience trouble learning a new language because their I-function is activated and is linked with a central pattern generator of the English grammatical rules. It takes this group of language learners to not think about English to override the I-function and create a new CPG for whatever language it is they are learning. This is why once they master the language and are totally immersed in it. Immersion in a different language forms a new CPG, which can override the old I-function or make their I-function accept the new path for the new language.
Learning a new language requires a mapping process for which infants are neurally prepared and which the brain's networks commit themselves to the basic features of the native language. These patterns allow phonetic and word learning. Infants that excel at detecting the patterns in natural language move more quickly toward complex language structures (2). By the exposure to a language early in development without producing it themselves has lasting effects on infants in their ability to learn that language as an adult.
Bilingual children are mapping two distinct systems with some portion of the input they hear devoted to each language. At an early age the I-function does not designate either language as the default, and so neither language's central pattern circuitry interferes with the other-allowing young children to acquire two languages easily (2).
Although the studies I used did not use the same neurobiological framework that we have been learning in class-the description of their concepts are consistent. This consistency validates the above mentioned findings as plausible explanations for the phenomena of children neurally being equipped to learn a) any language pattern and b) a number of languages at a time. By investigating this topic I have gained a greater appreciation for the I-function and CPG as are vital components of learning new languages and is applicable to learning other complex pattern based skills, like math. It also makes me realize that the filtering trait of the I-function is not necessarily what we would always desire. In the case of acquiring new knowledge the I-function can put individuals at a great disadvantage during the learning process.
The I-function can be limiting and not necessarily required for all desired actions. Our ability to still learn new things and new languages at this age does show that we have the capability of temporarily overriding our I-functions. Perhaps individuals who have speech/learning disabilities are unable to override their I-function and allow for new pathways or central patter circuitry to become established. These assumptions leave me with the following set of questions: What other factors come into play when overriding the I-function? Why is it that some people can override their I-function while others cannot? Why is it that some people can override their I-function for longer periods of times than others, i.e. speak a second language more fluently than others? What determines the discretion of the I-function, and does this differ from each individual?
1) http://serendip.brynmawr.edu/exchange/node/2118, Memory Inhibition: Some Functions of Forgetting, Submitted by Caitlin Jeschke on Mon, 02/25/2008
2) http://ilabs.washington.edu/kuhl/pdf/Iverson_Kuhl_2003.pdf, Iverson, P., Kuhl, P. K., Akahane-Yamada, R., Diesch, E., Tohkura, Y., Kettermann, A., & Siebert, C. (2003). A perceptual interference account of acquisition difficulties for non-native phonemes.
3) http://www.acfnewsource.org/science/learning_language.html, "Neuroscientists have discovered why children excel at learning languages"
4) Course Forum Area, Nervous system architecture: from the output side II