Dyslexia is one of several distinct learning disabilities. It is a specific language-based disorder characterized by difficulties in single word decoding, usually reflecting insufficient phonological processing abilities. The difficulties in single word decoding are often unexpected in relation to age and other cognitive and academic abilities; they are not the result of generalized developmental disability or sensory impairment. Dyslexia is manifested by variable difficulty with different forms of language, often including, in addition to problems reading, a conspicuous problem with acquiring proficiency in writing and spelling.
Simply stated, dyslexia is a type of reading disorder in which the student fails to recognize and comprehend written words. Dyslexia is a severe impairment in the ability to read, despite normal intelligence, normal opportunities to read, and an adequate home environment. Although the precise organic cause of dyslexia is unknown, it is generally thought that this problem results from difficulties with phonological awareness—a lack of understanding of the rules that govern the correspondence between specific sounds and certain letters that make up words (Lyon & Moats, 1997; cited in Gargiulo, 2004, p. 216). In other words, letter-sound recognition is impaired.
Various types of reading disorders have been recently cited by the American Academy of Special Education Professionals' Educator's Diagnostic Manual of Disabilities and Disorders (in press). Listed below are the reading disorders most frequently seen in children with dyslexia.
Direct dyslexia refers to the ability of the individual to read words aloud correctly, yet not comprehend what he or she has just read.
Such an affected individuals will have poor sight-word vocabularies and will rely on using time consuming word attack skills (a phonetic approach) to decode many words. As a result, students with this condition will read laboriously. Decoding becomes inaccurate for many phonetically irregular words, log for laugh . Characteristic spelling errors include phonetic equivalents for irregular words, such as rede for ready .
Children with the dyseidetic type of dyslexia are able to sound out individual letters phonetically but have trouble identifying patterns of letters in groups. Their spelling tends to be phonetic even when incorrect (laf for laugh). Children in this group have deficits in vision and memory of letters and word shapes, making it difficult for them to develop a sight vocabulary. However, they have the ability to acquire adequate phonetic skills.
Dyslexia with Dysgraphia ("Deep Dyslexia")
With this condition, a person has a problem in writing letters and words, grasping word-meanings, integrating the sounds of letters, and in pronouncing unfamiliar and, sometimes, even familiar words. People in this category face the biggest challenge and need our closest attention for educational and career planning.
Dyslexia without Dysgraphia ("Pure Dyslexia")
This disorder occurs when a person has problems reading but not writing. Some students with pure dyslexia have trouble doing written arithmetic because they have to read the text and the numbers, but may not have any problem doing spoken arithmetic. Dyslexia without dysgraphia may never be identified, because, to confuse matters, a person may have nearly normal oral language and his or her writing and oral spelling may be virtually unimpaired.
Dysnemkinesia involves minimal dysfunction of the area of the motor cortex involved in letter formation. Individuals with this disorder can be characteristically distinguished by their frequent letter reversals, such as d for b, as in doy for boy.
A type of dyslexia specifically associated with difficulties in naming and naming speed.
Dysphonic readers have difficulty relating letters to sounds, so their spelling is totally chaotic. They are able to recognize words they have memorized but cannot sound out new ones to figure out what they are. They may be able to read near the appropriate grade level but are poor spellers. Dysphonetic dyslexia is viewed as a disability in associating symbols with sounds. The misspellings typical of this disorder are phonetically inaccurate. The misreadings are substitutions based on small clues, and are also semantic.
Literal Dyslexia (Letter Blindness)
With this condition, a person has difficulty identifying letters, matching upper case letters with lowercase, naming letters, or matching sounds with the corresponding letters. Here, a person may read individual letters of the word but not the word itself, or read a word, but not understand the meaning of the word. Some people with literal dyslexia may read words partially. For example, a person may read the word lice as ice, or like.The person may realize that these words are incorrect, but cannot read the words correctly. Some people with literal dyslexia do better by moving their finger along the outline of a word, or by tracing the letters in the air.
Mixed Reading Disability Dyslexia (Alexic Reading Disability)
Children with mixed reading disabilities have both the dyseidetic and dysphonic types of reading disorder. This subtype combines the deficit of the first two groups. This person may have disability in both sight vocabulary and phonetic skills. People with this form of dyslexia are usually unable to read or spell.
This condition occurs when a person neglects the left or the right side of words, a problem particularly highlighted in reading long words. For example, if asked to read strowt,he or she may read it as owt. Given a word such as alphabetically, persons with this particular form of dyslexia will miss some of the first few letters. For example, they may read it simply as betically. There may be a problem with compound words. For example, a compound word such as cowboy may be read partially, as cow or boy .
This disorder occurs when an individual has difficulty in converting letters to their sounds. They can read words that are already familiar to them, but have trouble reading unfamiliar or novel words. They also have difficulty in reading a nonword such as tord. They may misread this nonword as a real word that looks similar. They sometime also misread actual words as other ones that look similar. The word shut may pose this particular problem, much to a listener's dismay.
This is a dysfunction of, rather than damage to, the left side of the brain (cerebral cortex) and does not change with maturity. Individuals with this type are rarely able to read above a fourth-grade level and may struggle with reading, spelling, and writing as adults. Primary dyslexia is hereditary and is found more often in boys than in girls.
This occurs when a person distorts the meaning of a word or incorrectly reads a word because of the confusion in the meaning of the given word. People with semantic dyslexia may say an antonym, a synonym, or a subordinate of a word instead of the word proper. For example, they misread dog as cat or fox. They may misread twist as twisted, or buy as bought. Some have trouble reading function words such as of, an, not, and and.
This occurs when a person has problems reading all types of words and sometimes has trouble identifying individual letters. Their reading is extremely slow and hesitant, particularly on long words. While a normal reader takes about 30 milliseconds for reading each additional letter, a spelling dyslexic may take about a second to do the same. Some dyslexics tend to read words one letter at a time, even if the words are short and familiar.
This condition occurs when a person can read words phonetically but has problems with whole word recognition (i.e., yacht = yachet).
This condition usually occurs after brain trauma or injury to the area of the brain that controls reading and writing. This type of dyslexia is rarely diagnosed in today's school-age population because they will often receive a classification in special education of Traumatic Brain Injury (TBI) rather than LD.
People with this condition usually cannot learn words as a whole component. There are problems with visual discrimination, memory synthesis, and sequencing of words. Reversal of words or letters when reading, writing, and spelling is common.
It is important to identify students with dyslexia or other severe reading disabilities early, before they fall far behind their peers in word-recognition skills. Students who appear to be learning letter-names, sounds, and sight words at a significantly slower rate than their classmates are at a risk for developing later reading problems. And yet, despite the enormous problems children with dyslexia face, the general consensus among researchers is that they can improve. When the diagnosis of dyslexia is made in the first two grades, more than 80% of the children are brought up to grade level. However, if the diagnosis is not made until the fifth grade, only 10 to 15% are helped (Kirk et al., 2003).
Finally, it is critical to remember that not all children with learning disabilities suffer from dyslexia. The term dyslexia is overused in the popular press, which often gives an inaccurate impression that everyone with a reading or literacy problem suffers from dyslexia.
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