Dyslexiais a condition that many institutions have had difficulty in defining due to itaffecting people in many ways and severities. Dyslexia is a learning difficultywhich “interferes with the acquisition and processingof language” (Gilchrist and Thompson 1997:5), which means peopleaffected by it struggle with reading and comprehending information that is secondnature to most. In this essay, Iwill firstly outline the dual-route model of reading to understand how a personwith dyslexia has a disrupted reading ability.
However, this essay will primarilyfocus on outlining acquired dyslexia, and how its subtypes impact a person’sability to acquire and process language. I will then go on to discuss why thesesubtypes have been proposed and come to a conclusion about how effective thesecategorisations are. Reading,is the processing of information and then attributing information into meaning.”Anyone who has successfully learned to read hasacquired a mental-processing system that can accomplish such transformations”(Coltheart 2005:6). Peoplewith dyslexia have either never been able to perform such transformations, orhave had injuries sustained to the brain that have impaired them. To understand reading and how we do it, it isimportant to understand this processing system. This process, can be exemplifiedby the dual-route model of reading.
This model is comprised of two routes and itoffers an explanation of the cognitive processes that take place allowing us toprocess print into semantic meaning. The direct route, or, lexical route, “involves looking up a word in a mental lexicon containingknowledge about the spellings and pronunciations of letter strings that arereal words” (Coltheart 2005:9). The direct route is required for the reading of irregular words.
Forexample, it would be necessary to read irregular verbs such as thrust, or spread. This is because theseexamples are not spelt phonetically, so the reader must rely on lexical knowledgeof the exceptional spellings of words to pronounce them. This semantic pathway developsthroughout life, increasing lexical knowledge throughout time. People withacquired dyslexia may have had this normal development prior to having impairmentsresultant of brain damage. Whereas, “reading via the nonlexical route makes noreference to this lexicon, but instead involves making use of rules relatingsegments of orthography to segments of phonology.” (Coltheart 2005:9).
Theindirect route is needed for reading unfamiliar words and pseudo-words. “A pseudoword is a fake word– that is, a string of letters that resembles a real word (in terms of its orthographic and phonological structure) but doesn’t actually exist in the language.”(https://www.thoughtco.
com/pseudoword-definition-1691549).Examples of such words include, cigbet, shum and dake. Tounderstand these words, it is not possible to rely on existing lexicalknowledge, because they do not exist in language. What is significant for thereading of these words are the rules of grapheme-phoneme correspondences.
This relatesto letters and letter strings which represent the individual sounds in language,therefore readers must sound out the letters in pseudowords individually to beable to process and read them. I will now move on to discuss acquired dyslexia, itssubtypes and how they relate to the dual-route model of reading. Acquireddyslexia affects a person’s reading ability and can occur because of brain damage.
There are three subtypes types of acquired dyslexia and each one affects anindividual’s ability to read in different ways. Phonological dyslexia is one ofthese subtypes. Those with phonological dyslexia will lack the phonologicalawareness required for the successful reading of pseudowords, “Phonological awareness refers to the realisation that wordsare made of a combination of smaller units (syllables and phonemes), and to theability to pay attention to these units and explicitly manipulate them.” (Ramus).Thus, they cannot read via the indirect route of the dual-route reading model,so they are incapable of making the connections for the rules of grapheme-phonemecorrespondence. However, there is no impairment in the direct route which meansthey can read real words in a language, both regular and irregular. Moreover, peoplewith phonological dyslexia often have other phonological impairments. They willstruggle to identify rhymes or confuse them, for instance, they will pronounce pint the same way as you would pronouncetint.
This suggests that phonologicaldyslexia is not just a result of grapheme-phoneme correspondence, but also a disruptionof phonological processing. Incontrast, surface dyslexia is another subtype that is the opposite to phonologicaldyslexia, It “typically arises from damage to the lefttemporal lobe” (Plaut 1999:547). Withinthis type of dyslexia those affected have no impairment to the indirect route,so they have the ability to read regular words and pseudowords. Albeit, unlikein phonological dyslexia there is an impairment in the direct route, meaning theycannot read irregular words such as, read,for instance. Additionally, “island willbe read as “iz-land,” yacht to rhyme with “matched,” and have to rhyme with”cave.
” Exactly this pattern is seen in some people whose reading has beenimpaired by brain damage” (Coltheart 2005:10). Those with surfacedyslexia “exhibit an interaction of frequency andconsistency in word reading accuracy, such that low-frequency exception wordsare pronounced disproportionately poorly, often eliciting a pronunciationconsistent with more standard spelling-sound correspondences (e.g., SEW read as”sue,” termed a regularization error).” (Plaut 1999:547). Indispute of this, individual differences affect how severely people experience acquireddyslexia, these can occur”not only from differences in the amount of semanticdamage, but also from premorbiddifferences in the division of labor between the semantic and phonologicalpathways”. (Plaut 1999:548).
Additionally, these categorisations are quite restricted, there is nota perfect double dissociation between both surface and phonological dyslexia. Manypeople with surface dyslexia can still read irregular words. This suggests thatthese categorisations do not take into account individual differences and couldbe considered outdated. There has been limited research into dyslexia,especially in adults, this means that there is some confusion in diagnosis. This brings me onto my next point ofoutlining deep dyslexia.
Symptoms of this type dictate that they are not easilyexplained by the dual-route model of reading. “Aphasic patients with deep dyslexia presentwith a number of generally co-occurring features or symptoms” (Coltheart1980:22). Similar to those with phonological dyslexia, people withdeep dyslexia have an impaired ability of the indirect route, which again meansthey are incapable of reading pseudowords. However, they also make semanticsubstitutions, or semantic paralexias, as well.
For example, someone with this typeof dyslexia would read the word duel butsay the word sword. This demonstrates “an almostcomplete inability to derive phonology directly from print (i.e.
, readnon-words), reading accuracy is affected by imageability/concreteness (highlyimageable/concrete better than low imageable/abstract words) and by the part ofspeech (typically, nouns > adjectives > verbs > functors).” (Grahamand Ralph 2000:141). Thishighlights how words that are more concrete and imageable, as opposed toabstract ones, are easier to form a more vivid mental picture of making themeasier to read. In continuation, people with deep dyslexia may have a damaged syntacticprocessing ability, so they’ll struggle with reading function words (such as the, or, and) and make morphologicalerrors.
It would be problematic to pronounce prefixes or suffixes, but the rootof the word would be correctly said so unrealwould be read as real.
