Double Dissociation and Language - Research Paper Example

 What does double-dissociation tell us about language development? What does double-dissociation tell us about language development? Language was developed as a single total phenomenon but when details were scrutinized, four systems in the brain were found to be involved in the materialization of language (Berninger, 2002). Language by ear (aural), language by mouth (oral), language by eye (reading) and language by hand (writing) were the different components. Relationships had been found between the reading and writing systems and they were divided into unidirectional and bidirectional. The interventional approaches for reading disability with or without writing disability were different. The mode of instruction and mode of response also varied for the different combinations of the disabilities (Berninger, 2002). Specific goals were to be set for accomplishing specified responses. Factors that influenced literacy skills and language development had been described by different researchers. Age had an inverse proportion with literacy skills. Home background and active use at work were other influences. This paper will be discussing about development of language in children, how they picked up language through their child hood, how instruction influenced their development and how functional brain imaging could change the learning lives of disabled children. Writing systems a) Phonographic systems Languages of the world were different in the mode of speaking but the graphemes of the writing systems had a co-relation. The phonemic writing systems could have symbols which corresponded to the language phonemes. The grapheme and the phoneme were on a one-one relationship in phonographic writing systems (Rogers, 2005). However this system was hardly practiced in any language. The alphabet ‘h’ was written but not pronounced in Spanish in some words. Learners had to find which morpheme was being written before proceeding to write such words. Spanish had only a few like this. However in the English Language, information on the morphology was essential as there was an immense number. There were several words which sounded the same but were spelt differently in writing: ewe, you, U in U-turn (Rogers, 2005). This explained why Spanish had little need for morphology while English needed too much of it for written language. The symbols of the writing system were known as letters and the whole system was called the alphabet. Alphabets, which included the punctuation marks, numbers, and the spacing between the words constituting the non-segmental graphemes, had significance. The English cultural heritage had used the Roman alphabet. The writing systems of the world were commonly using alphabets. Most languages used alphabets of the Roman, Greek and Cyrillic origin. The Indian, Arabic and the Hebrew systems were slightly different (Rogers, 2005). “A morae was a phonological unit intermediate between the phoneme and the syllable “(Rogers, 2005). Moraic writing had graphemes which were connected to morae. A syllable had an onsert, nucleus, and coda while the mora was made up of the either the onsert-nucleus or the coda. 2 morae made a ‘cut’. b) Morphographic systems The Chinese language indicated a primary association between the graphemes and the morphemes. This was the morphographic system. The graphemes were termed morphograms. Other writers had interpreted that the graphemes were related to words and not morphemes and the term logogram was used. Koreans had a featural writing. c) The non-segmental graphemic elements Writing also included some items which did not appear in speech but did so in writing (Rogers, 2005). Punctuational graphemes marked the boundaries. The English Language had capital letters at the start of the sentence which ended with a full stop or question mark or exclamation mark. Spanish marked the beginning of a sentence also for the same purpose. From personal experience, the Indians too did similarly for the ends of sentences; capital letters were not used. Tibetans used a raised dot for boundaries. The Chines separated the syllables to indicate boundaries. Recently they had adopted the English graphemes of punctuation (Rogers, 2005). The English Language Contrastic discrepancy was a feature of the English language. Indentation of paragraphs was another component of the English Language. The title was larger and centred. Page numbers were marked at the top or below the page. The footnote was a smaller number and raised. The table of contents was in the front of the book and the index was found towards the back. The writing could be different in styles. Polyphones were common in moraic systems and uncommon in alphabetic writing. There were certain contrasts which were not expressed in the writing system of the English Language. The phenomenon of heterographic homophony arose when different words with the same pronunciation and sound were written with different spellings like “seem, seam, cede, siege” (Rogers, 2005). Similarly there were examples of heterophonic homography. The word “read” could be pronounced as if the vowels were “ee” and also as in “red”. The syllables “ough” were pronounced differently in different words: “cough, tough, through, though” (Rogers, 2005). The syllables “th” in different words were similar sounding phonemes but when used in foothills, belonged to different phonemes and the sound was different., Just as in the English language, the contrastic discrepancy was a feature of all writing systems. The dual route theory of reading aloud Skilled adult readers possessed two routes for reading aloud. Coltheart’s dual route model of 1993 was the first of its kind to describe reading. This dual route was believed to have a lexical and non-lexical route (Jackson and Smith, 2008). The peculiarities of the English language, which had plenty of morphemes, required both the lexical and non-lexical routes for reading the language. Spanish, German and Italian readers, on the other hand, used the non-lexical route for reading aloud and the decoding was very fast as they had very few morphemes. For regular words, both routes produced the same pronunciation. However for irregular words, only the lexical route functioned to produce good pronunciations. The phonologic forms and the orthographic forms were connected through the lexical route (Coltheart, 1996). The non-lexical route functioned in the pronunciation of groups of letters, which were not words. Damage to one route could produce a language problem for certain words. The impairment of the lexical route produced good pronunciation of regular words and non-words but irregular words were read with errors or mispronounced (Jackson and Smith, 2008). The damage of the non-lexical route led to normal reading of regular words and the irregular words but the non-words were not read or read with different pronunciation. Impairment of the lexical route was the surface dyslexia. Phonological dyslexia occurred when the non-lexical route was impaired (Jackson and Smith, 2008). The dual route theory helped us to understand the disorders arising from selective damage. Double dissociation of reading The surface dyslexia and phonological dyslexia were examples of double dissociation of reading, which was a significant entity of language (Jackson and Smith, 2008). The dual route theory explained this dissociation. Surface dyslexia patients could read regular and non-words while irregular words were mispronounced. Phonological dyslexia patients read regular and irregular words but showed impaired reading of non-words (Jackson and Smith, 2008). The double dissociation was the result of separate processes for a single function like reading. This double dissociation was also reported in recognition of faces and visual objects. There could be separate processes or pathways for recognition of faces and of visually seen objects. Some people could recognize faces while others recognized visually seen objects when the other function was impaired. Cognitive neuropsychology had recognized double dissociation as significant and this could be due to the fact that different functions were incorporated in different anatomical parts of the brain. The main point was that the anatomical closeness of the different parts sub-serving the two routes could produce damage to both. Also it could be remembered that damage could affect the route which was more important. The more difficult task could be impaired. Double dissociations were better accepted arguments than the single route explanation (Coltheart and Davies, 2003 in Jackson and Smith, 2008). Cognitive functions had a connectionist model which scientists and philosophers followed as the networks of functions corresponded to the brain. The networks enabled learning. They could be damaged for various reasons; this was when double dissociation had occurred. Modularity was an idea accepted by connectionist thoughts. The connectionists proposed that the different words were read aloud and pronounced differently due to weights on the connections (Jackson and Smith, 2008). Research needed to investigate whether double dissociation had occurred when 2 cognitive tasks which were connected in some way was the result. However connectionists consider their own model only. They did not believe the double dissociation argument (Jackson and Smith, 2008). If 2 tasks were impaired, the resultant function could be due to double dissociation. Research had to explain this. Frith’s model of reading The progressive ability of children to read and write had been described using various models (Whitebread, 2002). Frith’s model was widely accepted. He had a stage theory for the language learning process. The stages were as follows. The progressive abilities of children were depicted in each stage. Table 1 Frith’s staging of reading and writing (Whitebread 2002) Step Reading Writing 1a Logographic Symbolic 1b Logographic Logographic 2a Logographic Alphabetic 2b Alphabetic Alphabetic 3a Orthographic Alphabetic 3b Orthographic Orthographic The young children read enthusiastically trying to remember the words that they saw. They then shifted to letter-phoneme relationships when they started writing. Phoneme instruction at this point could provide them a better strategy of mastering the alphabet (Whitebread, 2002). Soon their reading and writing prowess was increased. Realising that memorizing words was possible, they used that new facility to continue their learning. Larger amounts of stored information helped their reading and writing to progress speedily. Writing new words helped to memorise them faster. The first stages involved the children learning from visual forms. Later alphabetic forms were recognised as spoken words and visually seen words (Whitebread, 2002). These were remembered and copied. In the orthographic stage even non-phonic sequences were recognized and spelling began to take effect. Making sense out of their reading was the next step in the learning process. Collaborative experiences of reading in school, at home were shared together to increase the reading process (Whitebread, 2002). Other theorists believed that the process of learning in children were more like overlapping waves. The children had strategies of reduced and elevated efficiency working alongside each other. In course of time, the less efficient strategy could prevail (Whitebread, 2002). Difficulty of recognition of words This was the most significant of the features in dyslexia which was a specific disability of reading. Dyslexia was also known as word-level reading disability (Cornoldi and Oakhill, 1996). Other conditions which produced reading comprehension difficulties were language processing problems and low skills of reasoning. Problems in quick word recognition were evident in neuroimaging procedures. Phonological problems and orthography were linked to the development of word recognition. The word recognition disability arose due to poor phonological processing. There could be many factors which affected reading comprehension and the links between the orthographic, phonological and semantic processes could be focused upon for future research. Decoding and comprehension were interlinked in many ways (Cornoldi and Oakhill, 1996). Skilled reading meant skilled decoding and comprehension. Similarly a deficit was one of both. However for study purposes, the two could be dissociated. Distinct mechanisms had been identified for both decoding and comprehension. These two skills could be dissociated. The dyslexic understands reading but cannot decode. The hyperlexic behaved in the opposite manner. However both types of children could not read. The garden variety of reading disability had both skills impaired (Cornoldi and Oakhill, 1996). So reading ability or literacy occurred if both the decoding and comprehension were present. The reading ability could be valued as a product of comprehension and decoding. Listening and repeating a story could also be assessed as reading comprehension. Multiplying the decoding and the comprehension produced the multiplicative model. There was assumed to have been an additive model too. Of the two, the multiplicative model was better with listening comprehension than the additive model (Cornoldi and Oakhill, 1996). The reading comprehension was found to be better in the younger age group and it decreased over time. The youth in college found the comprehension better through listening but they did not appreciate the decoding. The co-relation between decoding and reading showed a reduction as time flew while the co-relation between listening and decoding showed a substantial increase. The study implied that reading had to be considered as a whole and had better not be broken down into sub-skills (Cornoldi and Oakhill, 1996) Interpretation of reading skills Researchers had identified some components for the development of reading (Paris, 2005). The alphabetic principle was the first. Phonemic awareness, which was mentioned earlier, was the second. Oral reading fluency was the third. Vocabulary and comprehension were the others. Comprehension was also mentioned earlier in this paper. The 5 skills and the model of implicit development had been the basis of the “No Child Left Behind Act” of 2002 (Paris, 2005). The significant ones were the alphabet principle, phonemic awareness and the reading fluency. These were the predictors for reading skills later in life. However they were noted to be constrained in theory and method. What does double-dissociation tell us about language development? Language development was dependent on the brain activity. The processing of language in the brain could be observed with modern neuroimaging techniques like PET (Positron Emission Tomography and fMRI (Functional Magnetic Resonance Imaging). The neural activity in the area which processed language was indicated by the blood flow in the region (Bear et al, 2007). The different language tasks were sub-served by different portions of the cerebral cortex as indicated by research. Brain imaging had shown that language processing was more complex than suggested by earlier studies. Neuroimaging had indicated that the language areas were the temporal and parietal cortex as indicated by studies of aphasia. However more information was obtained later in fMRI studies; the extent of activity was increased in both the dominant left hemisphere and the non-dominant. Variations were noted in spoken language, sign language and Braille (Bear et al, 2007). The dominant hemisphere was responsible for spoken language. The area sub-serving language was the Broca’s area or the motor area in the frontal lobe cortex. Any damage to the relevant brain area resulted in Broca’s aphasia where the patient had comprehension of language but could not articulate or spoke in an agrammatical manner without fluency. If the damage were in the Wernicke’s area of the posterior temporal lobe, the patient had Wernicke’s aphasia by which he spoke fluently and grammatically but the words were meaningless as comprehension became poor (Bear et al, 2007). The patient with global aphasia spoke very little and comprehension too would be deficient. Damage to the transcortical area in front of Broca’s caused aphasia with the same characteristics of Broca’s aphasia. Damage to the sensory cortex in the parietal, temporal and occipital areas produced aphasia similar to Wernicke’s. Newer concepts had been postulated later. The left peri-Sylvian cortex in the middle temporal lobe was involved with the selection of words from concepts (Bear et al, 2007). The left posterior temporal and inferior parietal lobes were associated with phonological code retrieval. The left posterior frontal lobe and the superior temporal gyrus were concerned with the post lexical phonological and articulatory processes (Bear et al, 2007). More research was being done to study the language processing in the brain. Repetition of spoken words was one task that was set for studying language processing. When the sounds were heard, the auditory system processed the sounds and sent sensory signals to the Wernicke’s area. Now for the meaningful words to be repeated, signals were sent from the sensory cortex in Wernicke’s area to Broca’s area through the arcuate fasciculus. The phonological code was retrieved to initiate muscular movements which produced sound. Simultaneously the nearby cortical areas initiated the movements of the tongue, lips and larynx. The person repeated the words heard. Written text when read aloud, the visual system carried the information to the higher cortical centres for vision via the striate cortex. The signals then moved to the angular gyrus which was situated close to the parietal, temporal and occipital lobes. From here onwards, the signals passed as in the task above: from Wernicke’s to Broca’s to motor cortex. The commissures known as corpus callosum were the points through which the hemispheres communicated. In a split brain, this communication was interrupted and the hemispheres behaved as separate organs (Bear et al, 2007). Some split-brain studies showed separate behaviors of each hemisphere and they were usually conflicting reactions. This indicated that the 2 hemispheres controlled independent functions. Both hemispheres could produce answers to questions addressed to each. Electrical stimulation of the brain to study language functions produced effects similar to damage of the areas. The stimulation of the motor cortex produced a sudden stopping of the speech (Bear et al, 2007). Reading development based on orthography The characteristics of each language influenced the reading development and disability (Joshi and Aaron, 2006). The phoneme-grapheme correspondence was one factor which influenced the language development. The pattern of the phonology was another. The morphological system also had an influence. However details about the influences had not been discovered yet. The linguistic-cognitive skills were influenced. The belief was that if orthographic transparency was maximum, the number of phonemes was almost the same as graphemes, the language became easier to study. If the numbers did not coincide, the language became more difficult to speak and write. The other features that produced difficulty were the lengths of the words, prosody and the distinctiveness of the phonemes and their representations. These problems became more evident in later life when speed turned out to be a factor for fluency. Reading happened when there was an integration of phonological and semantic processes (Joshi and Aaron, 2006). Phonological influences were considered more significant especially in training programmes. These were initially connected to orthography and later the semantics were taken up. Training in morphological awareness helped children to read. This awareness developed the orthographic knowledge. Morphological decomposition was a strategy for studying long words and compound words. A study for reading literacy was conducted for children of ages of 9 and 14 years by the International Association for the Evaluation of Education Achievement (IEA) in 1990-91. The children were investigated for narrative prose and domain of reading. Other domains examined were expository prose and document reading. Norwegian children scored above the International average but the Finland children were below it. However Finland children had the most transparent orthography surprisingly. For the overall ranking, Norway was far behind. Sampling bias could be a reason. The orthography of different languages affected the way children learnt the language. The Persian language had only 6 vowels (Baluch, 1992). Three vowels were represented by alphabets. The other three were written as diacritics which were smaller than letters. Two diacritics were situated above the letters of words and one below. The Persian or Farsi language had two different spellings, one opaque and the other transparent. Opaque words were mostly of consonants. There were also words which had vowels and they were transparent (Baluch, 2005). The opaque words were recognized and processed at deeper levels. The transparent words could be read through the lexical and non-lexical pathways. The Icelandic orthography had a literacy tradition that went back to the 12th century (Joshi and Aaron, 2006). The Latin alphabet had been adopted. Spelling reforms had taken place and there was a debate as to whether the spellings needed to be preserved from the olden days or whether they had to conform to the pronunciation (Joshi and Aaron, 2006). Currently the language was easy for study by children. The Norwegian alphabet had 40 phonemes and 29 letters. Twenty consonant phonemes also existed in the alphabet. Vocabulary was vast and spellings complex. Consonant clusters were present too. Apart from the two genders, there was a neutral gender too. The spellings of many words did not conform to the pronunciation making the study of that language a problem. A different type of large-scale study was conducted by the Programme for International Student Association (PISA) (Joshi and Aaron, 2006). The recall of specific information, interpreting of written matter, reflection of previous read matter and its evaluation were some of the features of the study. The theme was “reading to learn”. In overall ranking, Norway was 13th. Finland and Sweden were far ahead, even of the US. Reading competence improvement was the outcome. However the variations were greater among the Norwegian children. Girls were better in all countries. The positive attitude towards reading was least in Norway after US and Belgium. Girls were more positive. Conclusion The development of language had been described as a complex process. Decoding and comprehension skills were important in reading. The ability to write was also important for definition of literacy skills. It was understood that reading ability was different from reading literacy. Reading comprehension characteristics were laid early in life. Time was the factor which allowed the evolution of these skills which were dependent on the inborn characteristics of children and the environments at home and school. The skill of reading comprehension influenced the development of language and cognitive features and these in turn contributed to reading comprehension. The quality of school instruction predicted the skill of reading comprehension More research was required for improvement of reading comprehension in children who had learning disabilities. References: Baluch, B. (1992). Lexical decisions in Persian: a test of the orthographic depth hypothesis International Journal of Psychology, forthcoming. Baluch, B & Danaye- Tousie, (2005) Developmental dyslexia as a function of opaqueness and transparency of a word's spelling: Evidence from Persian. The Experimental Psychology Society meeting London 6-7 January 2005 Bear, M.F., Connors, B.W. and Paradiso, M.A. (2007). Neuroscience: Exploring the brain. Lippincott. Williams and Wilkins Berninger, V.W., Abbott, R.D., Abbott, S.P., Graham, S. and Richards, T. (2002). Writing and Reading: Connections between language by hand and language by eye Journal of Learning Disabilities, Vol.35(1): 39-56. Coltheart, M. (1996). Phonological Dyslexia: A Special Issue Of The Journal Cognitive Neuropsycholog. Pyschology Press. Cornoldi, C. and Oakhill, J. (1996). Reading comprehension difficulties: processes and intervention. Routledge 1996. Gazzaniga, M.S. (2004). The cognitive neurosciences. MIT Press Jackson, F. and Smith, M. (2008). The Oxford Handbook of Contemporary Philosophy. Oxford University Press. Jackson, N.E. and Coltheart, M. (2001). Routes to reading success and failure: Toward an integrated cognitive psychology of atypical reading. Psychology Press Joshi, R.M. and Aaron, P.G. (2006). Handbook of orthography and literacy. Routledge, Language Arts and Discipline. Lawrence Erlbaum Associates Inc. USA Paris, G.S. (2005). Reinterpreting the development of reading skills Reading Research Quarterly Vol. 40, No. 2: 184-202 April/May/June 2005. International Reading Association doi:10.1598/RRQ.40.2.3 Rogers, H. (2005).Writing systems: a linguistic approach Wiley Blackwell. Blackwell Publishing, USA, UK and Australia Whitebread, D. (2002) The Psychology of Teaching and Learning in the Primary School. 2nd Ed. Routledge.Taylor Francis eLibrary. (2001) Read More