What brain-based research tells us about second language learning

What brain-based research tells us about second language learning Andrea B. Hellman, Ed.D. Missouri Southern State University Project S.P.E.A.K. Objectives Participants will become familiar with the fundamentals of brain-based research on bilingualism. PW understand key findings. PW discern pedagogical implications for second language learning. Available at http://mssu.academia.edu/AndreaHellman/Talks What are the methodologies of neurolinguistics? Case studies of patients with language disorders. Electrocortical stimulation mapping during surgery. Brain imaging during experimental tasks. Brain imaging technologies EEG (electroencephalography) !! CAT (computerized axiomal tomography) !! PET (positron-emission tomography) !! MRI (magnetic resonance imaging) !! fMRI (functional MRI) !! MEG (magnetoencephalography) !! DBR (deep brain recordings) (Wahl et al., 2008) !! Only a few procedures are noninvasive !! EEG (ERP child laboratories) !! !! ERP (event related potentials): electrical activity recorded on the surface of the skull) MEG Limitations of neuroimaging !! !! !! !! !! Individual differences Difficult to generalize findings Images capture as one both activation and inhibition activity Difficult to compare across studies because there are different experimental tasks We do not know all the processes that are involved in completing complex experimental tasks (for example, listening to a story in language X) The outer layer of the brain is the cortex, which is made up of the bodies of brain cells (neurons). These brain cells emit action potentials when they become excited. This is a form of electrical activity, which can be recorded in time and space via electrodes that are attached to the skull with a conductor gel or in a special cap. A computer records the activity measured by each electrode. What can EEG (ERP) studies tell us? Particular mental activities elicit charateristic electrical signals on the surface of the brain. !! N400 effect = negative wave 400 milliseconds after a semantic violation in the centroparietal region !! P600 effect = positive wave 600 milliseconds after hearing a grammatical error !! Paradis, 2004 Osterhout, McLaughlin, & Bersick, 1997 What can EEG (ERP) studies tell us? N400 effect !! Semantic or pragmatic violation !! !! I take my coffee with cream and dog. Those spiders often burn new webs. Osterhout, McLaughlin, & Bersick, 1997 Osterhout, McLaughlin, Pitkanen, Frenck-Mestre, & Molinaro, 2006, p. 204 What can EEG (ERP) studies tell us? P600 effect !! Grammatical/syntactic violations !! !! !! !! The cats won’t eating the food. The elected officials hopes to succeed. The successful woman congratulated himself. I wonder which dress when the bride wore. Osterhout, McLaughlin, & Bersick, 1997 Osterhout, McLaughlin, Pitkanen, Frenck-Mestre, & Molinaro, 2006, p. 204 What do we know about language in the brain? !! The biological bases of language There is not one area in the brain that is responsible for language. Language is unique to the human brain. From an evolutionary standpoint, it is a fairly late addition to our neuroanatomy. Language “piggybacks” onto other sensory-motor functions. !! The human brain has three main parts: !! !! !! The cortex (primate brain) The limbic system/mid-brain (mammalian brain) Brainstem Pinker, 1994 The biological bases of language k||æ||t|= | !! Emotional content Meaning | | 0 17-35ms // | | 400ms !! Grammar | 600ms The cortex regulates cognition !! !! The limbic system carries the emotional functions !! !! A threatening message? > No. The cat will BAKE. The cat will EATING. !! !! Thalamus > Limbic system > Cortex Grey matter, thin layer of nerve cell bodies White matter, axonal projections that are covered in myelin Has more direct connections to sensory nerve cells than the cortex. Embedded in the limbic system is the thalamus (“original room”). This is a relay station for sensory information. This feature of the brain (thalamus) exists in birds and reptiles as well. The most basic feature of language that is organizes sensory experience. The Two Phases of Language Processing !! Phase I: Thalamic !! !! !! The Two Phases of Language Processing !! All language signals are filtered by the thalamus, which regulates and organizes sensory information. The thalamus relays info faster to areas that respond emotionally than to areas that organize information cognitively. Language processing is strongly tied to emotional processing. Phase II: Cortical !! !! !! Language signals from the thalamus are sorted and sent to different cortical areas for processing. These cortical areas are genetically specialized to process particular types of information. Broca’s area Wernicke’s area Wahl, Marzinzik, Friederici, Hahne, Kupsch, Schneider, Saddy, Curio, Klostermann, 2008 Broca’s area Wernicke’s area Involved in the motor production of language. !! Involved in the grammatical processing of language. (grammar = motor skill) (phonological and morpho-syntactic processing) !! !! Involved in spoken language comprehension. !! Involved in recalling content words. !! Responsible for making sense. (lexico-semantic processing) The area that corresponds to Broca’s area in the right hemisphere Involved in processing prosody (stress, rhythm, intonation. (prosodic processing) !! Aphasia = damage to language !! !! !! Left thalamic aphasia !! Global loss of spontaneous speech !! Can imitate language sounds, words, phrases Broca’s aphasia !! Difficulty with the physical aspects of speech, loss of fluency !! Agrammatism Wernicke’s aphasia !! Nonsensical speech !! Missing/nonsense content words The area that corresponds to Wernicke’s area in the right hemisphere Involved in perceiving the emotional content of messages. (emotive/pragmatic processing) !! What do we know about language in the brain? !! The human brain is designed both to accommodate new experiences and to compensate for trauma to the brain circuitry. This flexibility makes it hard to pin down where things (skills, facts) are in the brain exactly. Everything is stored in networks in multiple ways. What do we know about language in the brain? What do we know about language in the brain? !! Language messages are sensory messages that are registered by the thalamus and relayed to the limbic system as well as the cortex. From the thalamus, the relay center, the cortex is farther than the limbic system. The consequence is that we respond emotionally to messages before we process them for structure and content. !! We also remember more of the emotion than the message itself. !! What do we know about language in the brain? What do we know about language in the brain? !! Circuitry that is gets repeated use becomes stabilized. One way to stabilize and sharpen electrical signals is by myelinating the axons that forward the action potentials. This process involves the brain’s glia cells, which wrap the axons in a glue-like insulation. Once a circuitry is stabilized, it is harder to override it or reconfigure it; it becomes the default mode for processing particular stimuli. In general, the more efficient/skilled the brain is at a particular function, the smaller the area that gets activated to complete the task. When the brain is unskilled at a task, the activation is diffuse. !! By the later part of the first year, infants no longer process the actual physical qualities of sounds they hear; instead, they create phonemic categories. They collapse the physical qualities of sounds into categories that are meaningful for the language they are exposed to. This categorical perception makes it easier to remember and process speech. Categorical perception is a characteristic way humans process and remember any input. Kuhl, Williams, Lacerda, Stevens, & Lindblom,1992. What do we know about language in the brain? !! Language acquisition is strongly tied to emotions. Infants perceive the emotional content of messages before they can segment the speech flow. Emotions play a key role in language acquisition; they either drive or inhibit the process. What do we know about the multilingual brain? !! How languages are stored and processed in the brain depends on a number of variables: Simultaneous or sequential acquisition !! Age of onset of acquisition !! Balanced or dominant bilingualism !! Proficiency level !! Bloom and Beckwith, 1989; Fernald, 1989; Locke, 1993; Schuman, 1997; Caldwell-Harris, 2008 Also see Damasio (1994), Descartes’ error. What do we know about the multilingual brain? !! The different language skill areas (phonology, morpho-syntax, lexicon, semantics) are affected differentially by these variables (age of onset, proficiency, use). Weber-Fox and Neville, 1996 Neville, 2001 Sanders and Neville, 2003 Kim, Relkin, Lee, and Hirsh (1997); Wartenburger et al. (2003); Weber-Fox and Neville (1996); Sanders and Neville (2003); Hahne and Friederici (2001); Hahne (2001) What do we know about the multilingual brain? !! Low proficient language use is associated with a more diffuse response, greater area activation. !! Later learned languages activate a larger area than earlier learned languages. !! Efficient processing is more likely with earlier learned languages and with high-proficient languages. What do we know about the multilingual brain? For later learned languages, efficient processing is more likely in lexicon and semantics, than in phonology and morphosyntax. !! Efficient processing is a requirement for native level language skills. !! Separate vs. shared areas of processing Whether the L1 and L2 are processed in shared areas or separate areas of the brain is one dimension of efficiency. !! Processing L1 and L2 in a shared area is more efficient than using two distinct areas of the brain. !! Early-onset balanced bilinguals process L1 and L2 in shared areas (both in Broca’s and Wernicke’s area). !! Separate vs. shared areas of processing Separate vs. shared areas of processing Late-onset bilinguals generally process their L1 and L2 in distinct places in Broca’s area. !! However, with very high proficiency the processing pathways may merge even in Broca’s area. !! !! Kim, Relkin, Lee, & Hirsch, 1997 Wartenburger et al., 2003 Weber Fox and Neville, 1999 Sanders and Neville, 2003 Hahne and Friederici, 2001 Hahne, 2001 For a review, see Wattendorf and Festman, 2008 Early and late-onset bilinguals process their L1 and L2 in a shared area in Wernicke’s area. This still does not mean that the processing is not qualitatively different. !! !! Low proficient bilinguals process their L2 lexicon through their L1 lexicon High proficient bilinguals connect their L2 lexicon directly to concepts Relationship of L2 processing quality and variables Broca’s Wernicke’s Phonology Grammar Semantics Lexicon Balanced early-ons. Dominant early-ons. Balanced late-ons. Dominant late-ons. Low-prof. * ** A neurolinguistic theory of bilingualism (Paradis, 2004) !! Identical performance on behavioral language tasks does not mean that early and late bilinguals process the tasks identically. !! Early and late bilinguals differ fundamentally. High proficient late bilinguals use compensatory mechanisms to process language; they use speeded up control, rather than automatic processing. !! A neurolinguistic theory of bilingualism (Paradis, 2004) Procedural memory system The brain has two different types of memory systems: procedural and declarative. !! !! !! A neurolinguistic theory of bilingualism (Paradis, 2004) The procedural memory system serves skills (procedural knowledge = performing tasks automatically). The how of these processes is not available to consciousness. (For example, walking, driving, gymnastics, volleyball, typing, speaking.) The declarative memory system serves explicit knowledge (facts, concepts, events, mental representations, rules). These can be attended to at the conscious level. (For example, what you did yesterday, words, knowledge of geography, the rules of expository writing or pedagogical grammar.) Different types of bilinguals make different use of the subsystems. Phonology Monolinguals Balanced early bilinguals High proficient late bilinguals Grammar L L1 L1 Semantics L Declarative memory system Lexicon L Conceptual system Metalinguistic knowledge Not necessary except for formal registers and writing L L2 L1 L2 L1 L2 L1 L2 L2 L1 L2 L1 L2 L1 L2 Not necessary except for formal registers and writing Heavy reliance on this system for L2 Implications Implications !! Effortless acquisition and automatic processing are the privilege of early childhood. !! We need to reevaluate the definition of success in sequential, dominant, and lateonset multilingualism. !! Native level is not the goal; however, high proficiency is extremely beneficial for processing efficiency. !! !! !! !! Late-onset learners need phonological and grammatical training (metalinguistic knowledge and deliberate practice). Even so, an accent and grammatical errors are to be expected. Late-onset learners can be expected to achieve very high levels in L2 lexicon. Late-onset learners are vulnerable to age-related decline in declarative memory as declarative memory plays a key role in compensating for lack of automatice processing. Slabakova, 2006 Hellman, 2008 Paradis, 2004 Implications !! !! !! !! The emotional environment of language acquisition is a key to success. Emotion underlies both motivation and memory. It is essential that language learners feel positive both about the language itself and the learning environment (formal and informal). Negative emotions (embarrassment, fear, rejection, isolation) can sabotage a learner’s success. Schuman, 1997 Pavlenko, 2008 Caldwell-Harris, 2008 Discussion !! Creating a positive emotional climate for ELLs !! !! !! !! !! How do we ensure that students feel welcome and emotionally supported in our school and classrooms? What steps can we take to create an optimal learning environment for second language acquisition? 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S., Dupoux, E., Dehaene, S., Bettinardi, V., Cappa, S. F., Fazio, F., & Mehler, J. (1998). The bilingual brain: Proficiency and age of acquisition of the second language. Brain, 121, 1841-1852. CITATION FOR THIS PRESENTATION Hellman, A. B. (2009, November). What brain-based research tells us about second language learning. Presentation at the annual conference of the Missouri MELL, Kansas City, MO. Available at http://mssu.academia.edu/AndreaHellman/Talks CONTACT Dr. Andrea B. Hellman, Assistant Professor of Teacher Education (TESOL), Research Associate for Project SPEAK; Missouri Southern State University, 3950 E. Newman Road, Joplin, MO 64801-1595; andreabhellman@gmail.com