Applying Neuroscience to Academic Policy and Practice
Elizabeth R. Karow
Over the last two decades, neuroscience has given us the tools to fundamentally advance our understanding of the mechanisms and developmental sequences of language learning, and has demonstrated why certain concepts or content should be learned within defined developmental periods. This new understanding of the learning brain has also revealed some fundamental misconceptions and flaws in current educational policy and practice, specifically as they pertain to language learning and bilingualism.
Despite America’s long academic tradition of introducing second language in middle or high school, we have empirical evidence to support the conclusion that very young children are superior language learners. Not only do they have a precocious ability to acquire language, we can prove that children exposed to dual language in early childhood (ages 3-7) will significantly outscore their monolingual peers in cognitive skills associated with language and reading. The advantages are not limited to second language acquisition. In fact, the ability to manage two languages will alter brain development and produce marked advantages in working memory, ability to discriminate sound segments (phoneme awareness), a heightened ability to interpret intended meaning, to use context to make inferences, and to form integrated representations of text.
Despite the fact that an explosion of scientific evidence demonstrates the manifold benefits of early dual language instruction, the academic debate is complicated by current practice designed toward high stakes standardized testing at the secondary level. Additionally, discussion of the broader academic advantage of early dual language is often muted in the louder political debate regarding official language policy in the United States. Current practice and politics aside, it should be our goal to take advantage of the neurological predisposition of young children to learn critical language skills during critical periods, and to maximize the academic and intellectual potential of our students.
NEUROSCIENCE – Neural Mechanisms of Language Learning
New imaging technologies like functional near-infrared spectroscopy (fNIRS) and magnetoencephalography (MEG) , have enabled scientists to identify the areas involved with specific brain function, to “see” the learning brain. For the first time, we can begin to understand the process of learning, to map the specific areas of the brain that deal with function, content, and concepts, and to document the physical changes that learning causes in the structure of the brain. We can compare the brain at different developmental stages, to see how learning alters its structure over time and to gauge the most appropriate developmental periods for learning specific skills and concepts.
Dr. Laura Petito of the University of Toronto likens early childhood language acquisition to a symphony. “We can see it, and we sit there like a theater, or a musical concert, and watch the bass come in and the second fiddle and we watch all the parts of the orchestra come together to produce this miracle we call language.” (Petitto, 2010) This performance is staged largely within three regions of the brain just above, and in front of, the left ear. The first is the left superior temporal gyrus (LSTG), which is engaged in recognizing language sound segments called phonemes (of which human language has 44). The LSTG harvests specific sounds from what the baby hears, identifies them as the native language and moves them forward. Those chunks of sound will enter the left inferior frontal gyrus (LIFG) where different linguistics tasks are performed. One area of the brain puts sounds together into words, while another called Broca’s area looks up their meaning and determines if the word is a noun or a verb (morphology). A third area deals with the patterns in which words are used (syntax).
The present generation of cognitive neuroscience studies, which isolate the underpinnings of language processing in early learners, provides stunning proof for the classic psycholinguistic findings that young children do have an amazing capacity to discriminate the sounds of language.
CRITICAL PERIODS IN LANGUAGE LEARNING
A “sensitive period” is a developmental stage in which content or concepts are learned most efficiently while a “critical period” is a time in which specific skills must be learned. In the 1970’s, a British researcher established the concept of a critical learning period when he sewed kittens’ eyes shut for varying lengths of time and discovered that, although their optic nerves and eyes were fully functional, kittens who were blinded during the critical period were never able to recover their sight. They had not received visual stimulation at the specific time, or critical period, to lay neural pathways between the optic nerves and the brain. When no stimulation is present, the kittens’ brain will “prune” away unused areas to concentrate learning on more important skills. After this critical period, cats can be blinded for longer periods of time and still recover their sight, because the neural pathways were established during the critical period for sight in cats.
The first critical period for human language acquisition deals with the identification of sounds (phoneme awareness) and occurs between birth and twelve months. During this window of opportunity babies can identify all of the 44 phonemes across the entire spectrum of human languages. After the first year, however, they will only identify the sounds of their native language. Phonemes not introduced during this critical period will never be detectable. This inability to distinguish sounds is what causes “foreign” accents in adults even when they have spent almost their entire lives speaking a second language. “A human child from birth to six months has a universal capacity to discriminate any of the speech sounds in any of the world languages that it could have been exposed to.” (Kuhl, 2011) Between six months and a year, however, this capacity is diminished in one of the few aspects of human brain development where a child goes from better to worse. (Kuhl, 2011) Relative to monolingual children, bilinguals demonstrate an increased sensitivity to a greater range of phonetic contrasts, and an extended developmental window of sensitivity for perceiving these phonetic contrasts relative to monolingual children. (Petitto L. A., 2009.)
The perceptual abilities of infants and very young children are remarkably sophisticated and appear to be independent of any particular language. Young children (3-7) are simply prepared to learn language, and the brain’s early attention to speech, and the ability to classify its constituents, is a crucial ingredient in that process. “It is almost axiomatic in popular science that children have a privileged ability to learn a second language. The scientific jargon points to the presence of a “critical period” that enables children within its confines to enjoy a painless and successful journey to mastering a second language.” (Bialystok, 2001) The most obvious advantage is in the realm of phonology - the presence of a foreign accent. Intermediate sounds, which are typically the source of foreign accents, are a great problem for learners past the age of seven. Before that time, “the young language learner can create a new phonological category for the foreign sound irrespective of its relation to the known sounds of the first language. However, after that age, this ability is lost.” (Bialystok, 2001)
When researchers first discovered the critical period for processing language sounds, they hypothesized that playing video- or audio-tapes to babies would expose them to the sounds of other languages, and would equip them to hear those sounds later in life. As it turns out, that was not helpful at all. Although it is not yet fully understood, there seems to be a strong link between the social areas of an infant’s brain and those areas dedicated to phoneme discrimination. Dr. Patricia Kuhl, a professor of Speech and Hearing Sciences and co-director of the Institute for Brain and Learning Sciences at the University of Washington, has explored the question of why babies learn language from people, but not from screens. Previous research by her group showed that exposing English-language infants to someone speaking to them in Mandarin helped those babies preserve the ability to discriminate Chinese language sounds, but when the same exposure was given by computer, television, or audiotape, the babies learned nothing. “This special mapping that babies seem to do with language happens in a social setting. They need to be face to face, interacting with other people. The brain is turned on in a unique way.” (Klass, 2011)
A sensitive period in learning is when the brain is neurologically predisposed to process in its most efficient form, utilizing functionally specific areas. For language (both first and second language) the brain is equipped to effortlessly assimilate sound, syntax, morphology, semantics, and grammar during the specific development period of birth to seven, with some skills remaining until the age of ten. After that developmental period, second language acquisition is only possible using alternate, less efficient, and more mentally taxing neural strategies. In post childhood, the brain, no longer unable to tap into these functionally specific language centers must develop alternative pathways and depend heavily upon areas of the brain not designed to process language. This form of learning is similar to the recovery from neural injury or early sensory deprivation. For example, we know that many children have early visual, auditory, or social impairments from which they do recover later, but that learning happens in a different, less optimal, way than “normal” learning in children without these handicaps. By studying sensory deprived orphans from Russian and Romanian facilities, we know that certain emotional responses are the result of early social interaction, and that when babies are deprived of that normal interaction, their brains develop differently. With great understanding and effort, those children can sometimes overcome these deficits, but that early deprivation, and the subsequent emotional impairment, constitutes an example of a sensitive period. We know that there are both critical and sensitive periods in language acquisition and that “deprivation” of certain stimuli will make learning some language skills more difficult, and others impossible. “Language has a critical period for learning. Babies are geniuses until they are seven and then there’s a systematic decline. After puberty we fall off the map.” (Kuhl, 2011)
POST CHILDHOOD LANGUAGE LEARNING
Can post adolescents and adults learn a second language?
While neuroscientists assert that second language proficiency is accomplished almost exclusively during the critical period of early childhood, we can all name adults who have studied and mastered foreign language later in life. So, how is that possible? The narrow exception to this critical period theory is that a very small percentage of verbally gifted post-adolescent students can achieve near-native competence, although being gifted does not guarantee their success. “Whereas children are known to learn language almost completely through implicit domain specific mechanisms, adults have largely lost the ability to learn a language without reflecting on its structure and must employ alternative mechanisms, drawing especially on their problem-solving capacities to learn a second language. This implies that only adults with a high level of verbal and analytical ability and high intelligence will ever reach near-native competence.” (DeKeyser)
Foreign language teachers often complain that they need to teach English before they can teach another language because of the mechanical nature of current instructional methodology. Following the thought process for a typical Spanish language student, saying something as simple as, “Susie and I are happy today” involves determining that the subject “Susie and I” is the first person plural, that “are” will require the conjugation of the irregular verb TO BE, that the appropriate verb will be the transitive verb ESTAR rather than SER, that “happy” will need to be expressed in its feminine plural form, and to remember the vocabulary for all of it. It’s no wonder that only the highly gifted achieve any conversational ability with this academic model. Few of us are able to think that fast. Luckily, young children don’t need to be taught the mechanics of the second language. If they receive sufficient exposure during the critical period, they will assimilate tense, identification of subject, adjective agreement, and irregular verb forms, and they will do so without relying on the structure of the English sentences to form the same idea in a second language.
The ability to learn a second language continues to decline across the lifespan. When immersion occurrs as late as adulthood (post puberty), performance drops to levels slightly above chance. “Results suggest that whatever the nature of the endowment that allows humans to learn language, it undergoes broad deterioration as learners become increasingly mature.” (Jacquelin S. Johnson, 2002) (Christine M. Weber-Fox, 2006) Despite adult inability to hear “foreign” sounds and to naturally integrate morphology, syntax, and grammar, experts agree that vocabulary can be acquired at any age.
The regions of the brain which are designed to assimilate language are tasked with achieving certain skills in a certain order and at a certain time. A young child, exposed to more than one language before the age of seven, will process that second language the same way he/she processes the first language – utilizing the same physical areas of the brain to do so. This form of learning is almost effortless in comparison to later language learning which needs to rely on areas of the brain not functionally specific to language acquisition, but to memory and critical thinking.
Imaging reveals that later second language exposure will require greater bilateral activation, recruit more distributed frontal lobe tissue - including working memory, and will require more cognitive effort. Older learners will try to use their present knowledge system as an organizing structure, or scaffold, for the new language. This dependence upon the structure of the first language will also be an impediment to the assimilation of dissimilar syntax and grammatical structures. Post-adolescent bilingual exposure changes the typical pattern of the brains’ neural organization for language processing, but early bilingual exposure does not. “Within the frontal-lobe’s language-sensitive regions, Broca’s area, second languages acquired in post puberty are spatially separated from native languages. However, when acquired during the early language acquisition stage of development, native and second languages tend to be represented in common frontal cortical areas.” (Karl Kim, 2010.)