On language acquisition and brain development, neuroscience: Kuniyoshi Sakai
- Linguistics, IE linguistics, in particular, have to re-evaluate their foundations. It appears to me that the disciplines have made little progress primarily because not enough attention has been paid to general semantics, the way 'meaning' is apprehended in the child's mind. The metaphors unique to a civilization become crucial primarily because of the 'meanings' associated with objects and images of objects.Thus, if a rim of a narrow-necked jar shows up repeatedly on many epigraphs (aha, writing system !), what word would the child have associated with the image? I say, the word compound meant --was uttered and heard as -- kanda-kanka meaning: 'rim of jar'; also, 'copper fire-altar' (both meanings in Santali and many other bharatiya languages). Of course, munda, nahali substrates in the civilization coalesced with the dravidian and the prakrits. It should be no surprise that substate words such as sanga, tibira (priest, merchant) were found in the interaction zone: Mesopotamian civilization.As the child grew up on Sarasvati-Sindhu river valleys, from circa 6500 BCE (Mehrgarh finds of s'ankha bangle and ornaments in a woman's grave), in the bharatiya cultural milieu, the mleccha evolved in a linguistic area. Read more at http://protovedic.blogspot.com and http://spaces.msn.com/members/sarasvati97 Bharatiyo means 'caster of metals' (Gujarati). The earliest writing system is decoded. The language is mleccha (meluhha) which was used in the conversation between Yudhishthira and Vidura in Mahabharata, discussing the non-metallic killer devices in the lakshaagriha (house of shellac). It is not mere coincidence that mleccha-mukha in Samskritam means 'copper'; milakkhu in Pali also means 'copper'. We are dealing with a perfect writing system consistent with occam's razor, the rebus method of depicting images to connote similar sounding words with meaning. Yes, neuroscience is leading us on the right track of understanding language evolution without indulging in hypothetical speculations of a *IE or *PIE.We need to re-evaluate and accept the relevance of s'iksha of the Vedic, hindu tradition and incorporate it as part of the present-day educational curriculum in a multi-layered approach to study and research: s'ruti-tantrayukti-anubhuti triad or trivarga. (purvapaksha, scientific research design and personal experience as in Yoga).Dhanyavaadah.K.NEUROSCIENCE: ON LANGUAGE ACQUISITION AND BRAIN DEVELOPMENT
The following points are made by Kuniyoshi L. Sakai (Science 2005 310:815):
1) A child acquires any natural languages within a few years, without the aid of analytical thinking and without explicit "grammar" instruction as usually taught in school. The origin of grammatical rules should thus be ascribed to an innate system in the human brain . The knowledge of and competence for human language is acquired through various means and modality types. Linguists regard speaking, signing, and language comprehension as primary faculties of language, i.e., innate or inherent and biologically determined, whereas they regard reading and writing as secondary abilities.
2) Indeed, the native or first language (L1) is acquired during the first years of life through such primary faculties while children are rapidly expanding their linguistic knowledge . In contrast, reading and writing are learned with much conscious effort and repetition, usually at school. This ability may be influenced by cultural rather than biological factors. However, the existence of developmental dyslexics indicates that reading ability requires specific neural mechanisms , and a link between poor reading and impaired auditory resolution has been suggested .
3) It is therefore crucial to understand how distinct linguistic faculties develop in the brain throughout various ages. The typical development of L1 faculties correlates with a massive increase in brain volume during the first years. Speech in infants develops from babbling at around 6 to 8 months of age, to the one-word stage at 10 to 12 months, and then to the two-word stage around 2 years. Sign systems are spontaneously acquired by both deaf and hearing infants in a similar developmental course , starting from manual silent "babbling". However, these obvious developmental changes refer to language output. Speech perception and even grammatical knowledge develops much earlier, within the first months after birth.
4) A clear contrast among linguistic factors exists between L1 and a second language (L2). The L2 ability does not seem to take any determined steps of development, and it shows enormous individual variation. Whether L2 relies on the same dedicated mechanism of L1 is thus a matter of debate. An L2 can be mastered at any time in life, though the L2 ability rarely becomes comparable to that of L1 if it is acquired beyond the hypothesized "sensitive period" from early infancy until puberty (~12 years old). The notion of a sensitive period for language acquisition comes from the loss of flexibility for cerebral reorganization due to acquired aphasia after puberty.
1. N. Chomsky, On Nature and Language (Cambridge Univ. Press, Cambridge, UK, 2002).
2. M. T. Guasti, Language Acquisition: The Growth of Grammar [Massachusetts Institute of Technology (MIT) Press, Cambridge, MA, 2002].
3. A. A. Beaton, Dyslexia, Reading, and the Brain: A Sourcebook of Psychological and Biological Research (Psychology Press, Hove, UK, 2004).
4. M. Ahissar, A. Protopapas, M. Reid, M. M. Merzenich, Proc. Natl. Acad. Sci. U.S.A. 97, 6832 (2000).[Abstract/Free Full Text]
5. G. Morgan, B. Woll, Eds., Direction in Sign Language Acquisition (Benjamins, Amsterdam, 2002)
NEUROSCIENCE: GENES, SPEECH, AND LANGUAGE
The following points are made by Simon E. Fisher (New Engl. J. Med. 2005 353:1655):
1) Learning to talk is one of the most important milestones in human development, but we still have only a limited understanding of the way in which the process occurs. It normally takes just a few years to go from babbling newborn to fluent communicator. During this period, the child learns to produce a rich array of speech sounds through intricate control of articulatory muscles, assembles a vocabulary comprising thousands of words, and deduces the complicated structural rules that permit construction of meaningful sentences. All of this (and more) is achieved with little conscious effort.
2) The acquisition of language usually proceeds along robust lines without any need for explicit tuition, in stark contrast to other complex learned abilities, like reading, writing, and mathematics. However, a small minority of children are unable to acquire speech and language proficiency, despite growing up in language-rich environments and showing adequate performance in other areas, such as hearing and nonverbal cognition. For some of these children, early difficulties with communication resolve with age, but for others the problems continue into adulthood. Since modern society depends heavily on language and literacy skills, persistent impairment is often accompanied by wider problems in educational, social, and emotional development in later life.
3) Developmental communication disorders are diagnosed in an exclusionary manner (the presence of speech or language problems that cannot be explained by an obvious medical condition) and so encompass a wide variety of phenotypes. For example, linguistic deficits can be confined to expressive language or can extend to receptive abilities, although pure receptive impairment is seldom seen. When it comes to speech output, affected children may fail to produce sounds that would be expected on the basis of age and dialect, which may be associated with difficulties in the planning and execution of the fine motor sequences that underlie speech. This large variety of communication problems is reflected by diagnostic schemes that contain several distinct categories (expressive, mixed, phonologic, apraxic-dyspraxic, and so on). In practice, there frequently are coexisting disorders involving various types of impairment, and the boundaries between these disorders can be fluid; a person may move from one category to another at various stages of life.
4) Although the causes of these kinds of disorders remain largely elusive, familial clustering and twin-based heritability studies provide strong evidence of genetic influences. At the same time, it is clear that the observed phenotypic heterogeneity is underpinned by a mixture of genetic effects, which range from common risk alleles acting in a multifactorial framework to rare instances of highly penetrant point mutations behaving in a classic mendelian fashion. The dissection of such a complicated state of affairs calls on geneticists to use multiple complementary strategies of both a traditional and a novel nature. By adopting a variety of approaches, linkage studies of prevalent types of speech and language disorders have implicated several regions of the genome, most notably on chromosomes 3, 13, 16, and 19. The putative risk genes underlying these linkages have yet to be identified, but progress is encouraging.
1. Bishop DVM. Genetic and environmental risks for specific language impairment in children. Philos Trans R Soc Lond B Biol Sci 2001;356:369-380
2. Fisher SE, Lai CSL, Monaco AP. Deciphering the genetic basis of speech and language disorders. Annu Rev Neurosci 2003;26:57-80
3. Vargha-Khadem F, Gadian DG, Copp A, Mishkin M. FOXP2 and the neuroanatomy of speech and language. Nat Rev Neurosci 2005;6:131-138
4. MacDermot KD, Bonora E, Sykes N, et al. Identification of FOXP2 truncation as a novel cause of developmental speech and language deficits. Am J Hum Genet 2005;76:1074-1080
5. Lichtenbelt KD, Hochstenbach R, van Dam WM, Eleveld MJ, Poot M, Beemer FA. Supernumerary ring chromosome 7 mosaicism: case report, investigation of the gene content, and delineation of the phenotype. Am J Med Genet A 2005;132:93-100
New Engl. J. Med. http://www.nejm.org
ANTHROPOLOGY: ON THE ORIGINS OF HUMAN LANGUAGE
The following points are made by Gary F. Marcus (Nature 2004 431:745):
1) If, as Francois Jacob argued, evolution is like a tinkerer who builds something new by using whatever is close at hand, then from what is the human capacity for language made? Most accounts of the evolution of language have focused on characterizing changes that are internal to the language system. Were the earliest forms of language spoken or (like sign language) gestured? Did language arise suddenly? Or did it emerge gradually, progressing step by step from a simple one-word "protolanguage" (limited to brief comments about the "here and now") into a more complex system that combined individual words into structured meaningful sentences encompassing the future, the past and the possible -- as well as the concrete present? Regardless of how these questions are resolved, if we seek the ultimate origins of language, we also need to look further back, beyond the first protolinguistic systems, to whatever prelinguistic systems may have preceded any form of language.
2) Possible prelinguistic precursors might include systems for planning or sequencing complex events, categorization, automating repetitive actions, and representing space and time. In each case, there are parallels between candidate prelinguistic cognitive (or motor) precursors and systems found in language. For example, many animals are able to construct mental maps for navigation, and all known languages draw heavily on spatial metaphors. Thus, it is tempting to conclude that machinery for the mental representation of space plays some role in -- or is at the very least available to -- the machinery for language.
3) But parallels alone are not enough to establish shared lineage between two systems -- they could instead represent convergent (independent) evolution. For example, a language system could have evolved its own machinery for automating repeated tasks, independent of pre-existing machinery for automatizing other cognitive functions. A more telling way of establishing prelinguistic ancestry could come from evolutionary contrivances, properties of language that existed not because of some selective advantage, but simply because they have descended from ancestral systems evolved for other purposes. Just as the panda's thumb is not a true digit, but a modified sesamoid bone pressed into service for gripping bamboo, some properties of our capacity for language may be better understood not as optimal solutions to a system for communication, but as cobbled-together remnants of ancestral cognitive systems.
4) In language, one good candidate comes from the study of memory. According to an optimal design, if the capacity for understanding language were evolved from scratch, it would be possible to reliably retrieve individual bits of syntactic structure on the basis of their location in a hierarchical structure, independently of their content -- as in most digital computers. Instead, human language systems seem to rely on "content-addressable" memory, a form of memory -- widespread in the vertebrate world and with an apparently ancient evolutionary source -- that retrieves information directly on the basis of its content, rather than through location. Unlike a computer's binary-tree structure, content-dependent memory in mammalian brains is subject to degradation over time and to interference between similar or intervening items.
5) Human speakers are thus less likely to resolve the relation between "admired" and "the newspaper" in a sentence such as: "It was the newspaper that was published by the undergraduates that the editor admired," than in the briefer sentence "It was the newspaper that the editor admired." In languages such as English that lack rich case-marking, in most cases listeners can correctly interpret only two levels of embedding, not because of a strict limit on the size of representable binary trees, but because similar items become confused in memory.(1-5)
1. Christiansen, M. H. & Kirby, S. Language Evolution (Oxford University Press, 2003)
2. Gould, S. J. The Panda's Thumb (Norton, 1980)
3. Jackendoff, R. Foundations of Language: Brain, Meaning, Grammar, Evolution (Oxford University Press, 2002)
4. Marcus, G. F. The Birth of the Mind (Basic Books, 2004)
5. McElree, B. et al. J. Mem. Language 48, 67-91 (2003)