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The use of sound is one of the most common methods of communication both in the animal kingdom and between humans. Animals use vocalization and calls to communicate and share critical information about food, dangers and individual intentions. Vocalization in the animal kingdom, as far as we know, relies on relatively small vocabulary of sounds, and a newborn animal is ready to communicate with adult individuals almost immediately. In contrast, human speech is a very complex process and therefore needs intensive postnatal learning to be used effectively.
Furthermore, to be effective the learning phase should happen very early in life and it assumes a normally functioning hearing and brain systems. In fact, the integrity of the hearing system seems to be very important to the language learning process. Children who lose hearing capacity will suffer a decline in spoken language because they cannot hear themselves and lose an important auditory feedback.
Nowadays, scientists and doctors are discovering the important brain zones involved in the processing of language information. Those zones are reassembled in a number of a language networks including the Broca, the Wernicke, the middle temporal, the inferior parietal and the angular gyrus. The variety of such brain zones clearly shows that the language processing is a very complex task.
On the functional level, decoding a language begins in the ear where the incoming sounds are summed in the auditory nerve as an electrical signal and delivered to the auditory cortex where neurons extract auditory objects from that signal.
After hearing and analyzing sounds by the cortex, the temporo-frontal networks located in the left hemisphere will proceed to syntactic and semantic identification in order to classify words and find their corresponding themes. The next step is a sentence level analysis supported by the right hemisphere temporo-frontal networks.
The effectiveness of this process is so great that human brain is able to accurately identify words and whole phrases from a noisy background. This power of analysis brings to minds the great similarity between the brain and powerful supercomputers.
Why is it harder to pick-up a new language in adulthood? Neuroplasticity you said?
Until the last decade few studies compared the language acquisition in adults and children. Thanks to modern imaging and electroencephalography we are now able to address this question.
Recent findings showed that infants begin their lives with a very flexible brain that allows them to acquire virtually any language they are exposed to. Moreover, they can learn a language words almost equally by listening or by visual coding. This brain plasticity is the motor drive of the children capability of “cracking the speech code” of a language. With time, this ability is dramatically decreased and adults find it harder to acquire a new language.
The maturation of the infant brain is accompanied by myelination in different regions to achieve higher speed of neuronal communications. While this boosts the data transfer rates, it is believed that it also constraints cognitive functions and decreases the plasticity of the brain. As a consequence, with time it becomes increasingly harder for a growing young adult to learn new languages.
Scientists also believe that until the age of seven to eight years children can learn and speak a second language fluently and without any accent. However, after that age, the learning performances will gradually decline and accent is more and more obvious in a person speech.
Why some people are faster language learners than others?
It has been clearly demonstrated that there are anatomical brain differences between fast and slow learners of foreign languages. By analyzing a group of people having a homogenous language background, scientists found that differences in specific brain regions can predict the capacity of a person to learn a second language. For example, studies concluded that morphology and size of the auditory cortex can predict our phonetic learning capacity while the connections between auditory cortex and specific parietal regions can inform us about the speech sound capability.
Whilst it is not yet clear if the morphological or connective variations in children will affect their capacity to learn a foreign language in adulthood, some scientists strongly believes that such anatomical variations can seriously influence our learning curve.
Native and second language brain zones: how do they work and where are they located?
Functional imaging of the brain revealed that activated brain parts are different between native and non-native speakers. The superior temporal gyrus is an important brain region involved in language learning. For a native speaker this part is responsible for automated processing of lexical retrieval and the build of phrase structure. In native speakers this zone is much more activated than in non-native ones.
The brain of a second language learner is forced to use more resources to decode a foreign or a second language speech. In this situation, the inferior frontal gyrus is activated to cope with the new language and try to identify the meaning of words and sentences.
Language acquisition is a long-term process by which information are stored in the brain unconsciously making them appropriate to oral and written usage. In contrast, language learning is a conscious process of knowledge acquisition that needs supervision and control by the person.
A native user of a language barely uses conscious processes to communicate making the expression of ideas fluent and coherent. On the other hand, to produce a phrase in a foreign language, firstly the unconscious process is triggered and then the conscious mechanisms are used to correct and adapt the sentence. It is clear that the conscious processing of a language materials is effort- and time-consuming and needs to be triggered by the person. As a result, it is much harder for a non-native speaker to reach a level of fluency equal to a native language speaker.
Despite the fact that brain structure can modify the way we learn new materials, it is necessary to understand that during the phase of language acquisition social interactions are crucial to the process. This hypothesis is confirmed by scientific data that showed a strong relationship between an infant social behavior and his or her capacity to gain new language concepts and vocabulary. Autism is an example of condition where a child who is lacking the necessary social interactions for encoding language materials will struggle to make communication fluent and correct.
Casey BJ, Giedd JN, & Thomas KM (2000). Structural and functional brain development and its relation to cognitive development. Biological psychology, 54 (1-3), 241-57 PMID: 11035225
Dehaene-Lambertz G, Dehaene S, & Hertz-Pannier L (2002). Functional neuroimaging of speech perception in infants. Science (New York, N.Y.), 298 (5600), 2013-5 PMID: 12471265
Friederici AD (2002). Towards a neural basis of auditory sentence processing. Trends in cognitive sciences, 6 (2), 78-84 PMID: 15866191
Golestani N, Molko N, Dehaene S, LeBihan D, & Pallier C (2007). Brain structure predicts the learning of foreign speech sounds. Cerebral cortex (New York, N.Y. : 1991), 17 (3), 575-82 PMID: 16603709
Kuhl PK, Tsao FM, & Liu HM (2003). Foreign-language experience in infancy: effects of short-term exposure and social interaction on phonetic learning. Proceedings of the National Academy of Sciences of the United States of America, 100 (15), 9096-101 PMID: 12861072
Newport, E. (1990). Maturational Constraints on Language Learning Cognitive Science, 14 (1), 11-28 DOI: 10.1207/s15516709cog1401_2
Paus T (2005). Mapping brain maturation and cognitive development during adolescence. Trends in cognitive sciences, 9 (2), 60-8 PMID: 15668098
Petitto LA, & Marentette PF (1991). Babbling in the manual mode: evidence for the ontogeny of language. Science (New York, N.Y.), 251 (5000), 1493-6 PMID: 2006424
Rodriguez-Fornells, A., Cunillera, T., Mestres-Misse, A., & de Diego-Balaguer, R. (2009). Neurophysiological mechanisms involved in language learning in adults Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1536), 3711-3735 DOI: 10.1098/rstb.2009.0130
Rüschemeyer SA, Fiebach CJ, Kempe V, & Friederici AD (2005). Processing lexical semantic and syntactic information in first and second language: fMRI evidence from German and Russian. Human brain mapping, 25 (2), 266-86 PMID: 15849713
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