• Poor overall decoding, sight vocabulary, and/or phonics. Decoding is the ability to identify what printed words are (i.e. the ability to read words). Decoding in turn is based on sight vocabulary and phonics. Sight vocabulary refers to words one recognizes instantly without having to sound them out. Phonics refers to knowledge of the sounds that different letters and letter combinations make.
• An over-reliance on sight vocabulary. This refers to students who have weak phonics and rely on having memorized words (i.e. sight vocabulary) in order to read. Although sight vocabulary is important, an absence of phonics skill is a problem for several reasons. For a word to be a sight word, the student must have seen the word many times. Education, by its very nature, continually introduces students to new and unfamiliar words and terms. Therefore, a lack of phonics knowledge interferes with the student’s ability to sound out unfamiliar words – words to which the student has never or only infrequently been exposed. This is especially the case in vocabulary dense areas such as Science and Social Studies as well as in English Language Arts in which students encounter many words they don’t usually see or use in conversation (e.g. words like “photosynthesis” or “dire”).Over-compensating with sight vocabulary can hide dyslexia and make it “go under the radar.” The student may know just enough words to get by. The student’s phonics difficulties may not be apparent when the student is reading text with relatively common words (e.g. a magazine or a newspaper) that place a low demand on phonics. An over-reliance on sight vocabulary also can be the case for older students who are no longer asked to read aloud and whose phonics skills are no longer being monitored.
• Poor reading fluency. Reading fluency refers to the speed and automaticity with which one can read. Poor reading fluency also can be a “hidden dyslexia,” particularly for students in the later grades, where reading speed is no longer being assessed and the length of time the student takes to read would not necessarily be something the student’s teachers and even parents might know. For example, how long it takes a high school student to complete a reading assignment is not something to which most teachers would be privy. For some students, a deficit in reading fluency comes to light when there is all of a sudden the demand for quick reading, like when prepping for the SAT or ACT. This can be especially the case when the student’s teachers have been informally giving the student extra time to complete classroom tests all along.
• Poor spelling. In dyslexia, poor spelling can result from the fact that the student has trouble accurately identifying all the sounds of the target word and/or the student has trouble remembering the letters/letter strings used to represent certain sounds. For example, a student may spell “kept” as “ket,” in which s/he did not “hear” in his or her mind the /p/ sound in the word and thus omitted it. As another example, a student may spell a word like “when” as “wen,” not recalling that there is a silent “h” in the word. The latter type of spelling errors are examples of breakdowns in the visual aspect of orthographic coding (see “What Happens in dyslexia” for further explanation).It is important to point out that, although most people with dyslexia have an impairment in decoding, students also can have dyslexia that only affects their spelling, that is, dyslexia with average decoding skills but impaired spelling. As noted by Dr. Virginia Berninger and colleagues, leaders in the area of learning disability research, “although dyslexia is often thought to be a reading problem, the persisting problem is spelling.”ⁱ

ⁱ Berninger, V. W., Richards, T., & Abbott, R. D. (2015). Differential Diagnosis of Dysgraphia, Dyslexia, and OWL LD: Behavioral and Neuroimaging Evidence. Reading and writing, 28(8), 1119–1153. https://doi.org/10.1007/s11145-015-9565-0

• Poor phonological processing.
• Poor word retrieval. Word retrieval refers to a person’s ability to recall words or “find the words one is looking for.” Rapid automatized naming (RAN) is an aspect of word retrieval important for reading fluency
• Poor alphabet mastery. Difficulty learning the alphabet, that is, naming the letters, writing them from dictation, and knowing the sounds that the letters make.

Research has indicated that up to 80% of the cases of dyslexia are caused by genetics. One way that genes cause dyslexia is by disturbing “neural migration,” which is the way the brain cells travel and organize themselves in the fetus during brain development inside the womb.ⁱⁱ

ⁱⁱ Schumacher, J., Hoffmann, P., Schmäl, C., Schulte‐Körne, G., & Nöthen, M. M. (2007). Genetics of dyslexia: the evolving landscape. Journal of Medical Genetics, 44(5), 289–297.

Yes. A child with a parent who has dyslexia has about a 40 – 60% chance of developing dyslexia. In addition, for a child with a sibling who has dyslexia, the risk of developing dyslexia is 3 – 10 times greater than that of the general population.ⁱⁱ

ⁱⁱ Schumacher, J., Hoffmann, P., Schmäl, C., Schulte‐Körne, G., & Nöthen, M. M. (2007). Genetics of dyslexia: the evolving landscape. Journal of Medical Genetics, 44(5), 289–297.

Dyslexia reflects dysfunction or a breakdown in one or more aspects of orthographic processing. Orthographic processing is the brains ability to make, retain (i.e. remember), and retrieve or “activate” orthographic codes.

An orthographic code is the representation of written words in memory. The orthographic code is what the person knows about the word – how the word sounds when it is spoken, how the word looks when it is written (i.e. it’s spelling), and the word’s meaning. You can think of an orthographic code like folders and the files within them on your computer. Each word you know is like a folder and each aspect of the word (the word’s sound, spelling, and meaning) is like a file within the folder.

Orthographic coding involves the brain connecting these different types of information. To create an orthographic code of a word, the brain must pull together different types of information, such as connecting sound and sight as when a child learns the sound of a printed letter. In order read and write, the orthographic code must be encoded or imprinted in memory to begin with, retained, and retrieved.

For example, the orthographic code of the word “fortune,” includes the fact that the word ends in the sound /chun/ and that, in this word, the letters “t-u-n-e” are used to represent that sound. To be able to decode or spell the word correctly, one must have formed this orthographic code in the first place, retained it, and be able to retrieve it. Otherwise, for example, when encountering the printed word “fortune” one might decode it “for – toon” or, when attempting to spell it, one might spell it “forchun.” To read and spell, one must have knowledge of the sounds and sight associated with that word (i.e. the letters or visual representation of the word).

There are different forms of dyslexia based on where the breakdown in orthographic processing occurs.

In order to engage in orthographic processing, the brain must perform different types of functions or underlying cognitive abilities. A dysfunction in any one or more of these functions can cause a breakdown in orthographic processing and thus cause dyslexia.

Some of the important brain functions necessary for orthographic coding include phonological processing, rapid automatized naming (RAN), and memory.

Phonological processing refers to the brain’s ability to process the sounds of words. Phonemes are the meaningful sound units out of which words are built. Phonological processing involves the brain’s ability to process phonemes. It includes the ability to isolate specific sounds in words (e.g. being able to hear that /c/ is the first sound in the spoken word “cat”), blend sounds (e.g. being able to combine the /b/ and /l/ in the word “bloom”), segment words into their component sounds (e.g. being able to identify that the word “cap” can be broken down into sounds /c/ – /a/ – /p/), and mentally manipulate sounds (e.g. realizing that if one deletes the /l/ from “clap” the new word would be “cap”).

Phonological processing is necessary for the sound part of the orthographic code. For example, to learn that the letter “b” says /b/, the letter “a” says /a/, and the letter “t” says /t/, one must first be able to “stretch” spoken words and isolate and identify the individual sounds that comprise spoken words, such as “bat.” Thus, phonological processing is necessary for the sound part of the orthographic code and a weakness in phonological processing can therefore cause dyslexia.

Rapid automatized naming (RAN) refers to the speed and efficiency that one can name things (e.g. how quickly a person could name the objects in one’s room – “lamp,” “rug,” “table,” etc.). RAN is one pre-requisite skill for reading fluency because it enables quick sight word reading, allowing the reader to quickly “name” printed words as a whole, that is, say what the printed word is “called.” For example, upon seeing the letters “w – h – a – t” on the page, RAN enables the individual to quickly recall that the word for that letter combination is “what.”

Visual memory is another ability underlying orthographic coding, enabling the “sight” part of the code. Visual memory allows the written letters that are used to represent different sounds to be encoded into memory. This is particularly important for irregular phonics patterns in which letters are used to represent sounds different from the sounds they typically make. This includes “trick” words, such as “was” in which the letter “a” makes the sound of a “u.” Irregular phonics patterns also include letter-sound patterns that contain silent letters. Learning such phonics patterns requires the work of visual memory. For example, there is nothing in the sound of the word “light” that tells you that there is a silent “g” and “h” in the word. Rather, you have to remember what the word looks like, the task of visual memory.

The Visual word form area (VWFA) also enables the sight part of orthographic processing. The visual word form area is located on the bottom, underside of the left side of the brain, in a part called the “fusiform gyrus.” The visual word form area performs a visual analysis of word fragments larger than letters. It helps us recognize the “parts” of words, such as prefixes, suffixes, roots, and other letter strings, such as “-ould” in words like would, could, should, etc.

The visual information received by the eyes is relayed to the back of the brain for analysis, a part of the brain known as the occipital lobe. The occipital lobes provide basic information such as telling us the shape and color of what we’re looking at as well as if it’s moving or stationary. The occipital lobes then send the information forward to other areas of the brain for further analysis, including to the parietal lobe, which is located on the top, back portion of the brain.

One important function of the parietal lobe is visual – spatial skill. Visual – spatial skill can be loosely defined as the ability to understand and appreciate location and position. Visual – spatial skills are used, for example, to put a puzzle together or understand a diagram.

Spatial orientation is an aspect of visual-spatial skill that refers to the ability to determine the correct direction (e.g. right vs. left, up vs. down) of information as well as the correct order of information (e.g. the sequence of letters in words). A weakness in spatial orientation causes errors such as reversing letters and numbers (e.g. confusing “b’s” and “d’s”) as well as transpositions. Transpositions refer to switching the sequence of information, such as perceiving “cloud” as “could,” in which the letter sequence l – o – u has been switched to o – u – l. Dysfunction in spatial orientation causes the person’s brain to “misinform” him or her of the direction or sequence of information. This also can interfere with math. In math, location often determines meaning, such as knowing which number goes on the top versus the bottom in fractions (e.g. 1/3 vs. 3/1) or in what direction to travel when solving multi-digit computations.

Reversals and transpositions are developmentally normal in children, to an extent, up until about age 7 years. Neuropsychological tests are useful in determining if and to what degree a child’s reversals or transpositions are beyond normal limits for children younger than 7 years, for whom it is normal to produce some of these errors.

Not necessarily. There are different types of dyslexia and the most common forms of dyslexia do not involve reversing letters. However, despite recent misconceptions to the contrary, a tendency to make reversals and transpositions is a form of dyslexia that can occur by itself or in conjunction with other forms of dyslexia.

It is important to point out that, with the increasing emphasis on the role of phonological processing in dyslexia in recent years, it is not uncommon for those in the fields of education and learning disabilities to go so far as to argue that poor phonological processing is the only cause of dyslexia and that visual processing, including reversals and transpositions, has nothing to do with dyslexia (e.g. “We used to think dyslexia involved reversing letters, but we now know it’s all caused by poor phonological processing.”). This is analogous to saying “We used to think that factories cause pollution, but we now know its cars that cause pollution.” Obviously both cause pollution.

The same is true regarding the roles of phonological and visual processing in dyslexia – impairments in one or both can cause dyslexia. There are multiple bases behind the above statement.

Firstly, some have argued that reversals and transpositions only exist because of poor phonological processing and that when phonological processing is improved, these reversals and transpositions disappear. This may be true for some individuals, but does not explain or account for the many individuals who have always had average to above-average phonological processing and still produce reversals and transpositions beyond developmentally normal limits.

Secondly, poor phonological processing does not explain transpositions that have nothing to do with the sound of the word, such as when children transpose silent letters. One cannot say that a child who spells “ghost” as “hgost” misplaced the “h” because s/he incorrectly processed the sounds of the word when the word does not have an “h” sound. Rather, such an error is purely one of confusing a visual sequence, the sequence of the written letters.

Thirdly, phonological processing also does not explain why individuals transpose words (e.g. saying “I want to dog walk…I mean walk the dog”) or why individuals who reverse and transpose often produce “conceptual reversals,” such as saying “breakfast” when they mean “dinner” or saying “summer” when they mean to say “winter” when in both instances the individual is correctly saying (i.e. correctly identifying the sounds of) each word.

Fourthly, phonological processing also does not explain why individuals who reverse and transpose often confuse direction in math (e.g. solving the problem left to right instead of right to left, subtracting the top number from the bottom number in multi-digit subtraction, confusing the numerator with the denominator, etc.) when these concepts have nothing to do with sound.

Fifthly, and perhaps most importantly, educational research and especially neuropsychological research, in particular brain imaging studies, continues to indicate that phonological and visual processing systems (as well as others) are necessary for reading and spelling and an impairment in either or both can lead to dyslexia. As but one example, as noted above, it is well established in neuropsychology that the left fusiform gyrus contains a “visual word form area” that analyzes words visually and that damage to this area causes alexia – a loss of ability to read in previously reading individuals.

Finally, the role of visual processing in dyslexia makes conceptual sense as well, since it is not logical to argue that dyslexia, a dysfunction involving processing visual stimuli (i.e. printed text), cannot have anything to do with visual information processing.

Reading comprehension is the ability to understand what one has read. Dyslexia interferes with reading comprehension in that one cannot be expected to understand the meaning of words one is not able to read in the first place.

In addition, dyslexia can impact reading fluency, the speed and automaticity with which a student can read. Even if a child can ultimately identify all the words (i.e. can decode them), poor reading fluency interferes with reading comprehension. By the time the reader gets to the end of the sentence / passage, s/he is likely to forget what was stated at the beginning of the sentence / passage.

Moreover, poor reading fluency interferes with a student’s ability to read with rhythm, which also gets in the way of comprehension. As an analogy, imagine how difficult it would be to understand a speaker who is slowly speaking one word at a time.

In addition, because poor reading fluency increases the time and mental effort it takes to read, it can increase frustration and cause the emotional “shut down” parents and teachers so often see in children with learning challenges. More time and mental effort to read also puts a greater strain on attention. Think of how much harder it is to pay attention for long periods when something takes a lot of “brainpower” compared to when it requires relatively less brainpower. The worse a person’s attention is, the worse their reading (or any academic skill) can become, creating a snowball effect – poor fluency causes poor attention which causes worse fluency, etc.

Yes. This is known as “co-morbidity,” or the degree to which two disorders co-occur. Dyslexia is not uncommonly co-morbid with other conditions. For example, an estimated 40% of people with dyslexia also have dyscalculia, a mathematics-based learning disability, and an estimated 30% of people with dyslexia have Attention Deficit / Hyperactivity Disorder (ADHD).ⁱⁱⁱ

ⁱⁱⁱ From: dyslexiaida.org

• Family history. Genes are thought to cause up to 80% of the cases of dyslexia and a child with a parent who has dyslexia has a 40 – 60% chance of having dyslexia.ⁱⁱ
  
• History of frequent ear infections / excessive fluid in the ears / tubes placed in the ears. These are risk factors for later impairment in phonological processing, a key ability necessary for the development of phonics, knowledge of the sound(s) that letters and letter combinations make. It is thought that ear infections and excessive fluid in the ears alter the sound signals sent to the brain, thereby interfering with the brain’s ability to receive appropriate auditory stimulation during formative years necessary to develop proper phonological processing.
• Smoking and alcohol consumption during pregnancy. Substance use, such as smoking and alcohol consumption, place a child at risk for a range of later learning problems, including reading difficulty. (This being stated, smoking has an even greater association with ADHD and fetal alcohol exposure has an even greater association with math difficulty).
• History of motor coordination difficulty. Children with dyslexia have long been observed also to have motor coordination difficulty. More recently, the cerebellum, which plays an important role in motor coordination, has repeatedly surfaced in research studies, including brain imaging studies, as an area of brain dysfunction in people with dyslexia. This is particularly interesting since this includes studies in which the cerebellum has popped up as an affected area even when researchers were not anticipating or looking for the cerebellum’s involvement.The fact that the cerebellum is involved in motor coordination and appears to be involved in reading is likely the reason why a history of motor coordination difficulty is associated with an increased risk of later reading difficulty. It is not uncommon if a person has difficulty in one ability also to have difficulty in another ability performed by the same general region of the brain. The particular way in which the cerebellum is involved in dyslexia has yet to be articulated, however, based on the research to date, Dr. Petrosky has a theory of the nature of this relationship, about which he has upcoming plans to write.
• Poor facial recognition. The visual word form area, which plays a role in sight word reading, is located in the same general area of the brain that plays an important role in recognizing faces. Therefore, if a person has dyslexia caused by dysfunction in the visual word form area, it increases the likelihood that s/he will also have trouble recognizing faces since this function is also performed by the same general region of the brain.
• Left-handedness. The right hemisphere or side of the brain controls the left side of the body and the left hemisphere of the brain controls the right side of the body. It is theorized that at least a portion of individuals who are left-handed were genetically wired (i.e. “supposed”) to be left-hemisphere dominant and thus right-handed (because the left hemisphere controls the right side of the body). It is theorized, however, that in certain left-handed individuals, something happened in-utero to disturb the left hemisphere. This caused the brain to compensate by making the right hemisphere stronger. This in turn made the right hemisphere become the dominant hemisphere, making the person left-handed (because the right hemisphere controls the left side of the body). This is known as the right-shift theory of handedness. For the vast majority of individuals, language is controlled by the left hemisphere. Therefore, according to the right-shift theory of handedness, since left-handed individuals had something happen to the left hemisphere, left-handedness can be associated with difficulties in certain language-based tasks, such as reading, because these abilities are controlled by the left hemisphere.
• Tics. One study found that 20 – 30% of the children in their sample who had tics had reading difficulty and vice versa.^iv

ⁱⁱ Schumacher, J., Hoffmann, P., Schmäl, C., Schulte‐Körne, G., & Nöthen, M. M. (2007). Genetics of dyslexia: the evolving landscape. Journal of Medical Genetics, 44(5), 289–297.

^ivJensen, J. (2005). Neuropsychological and behavioral characteristics of children and adolescents with Tourette Syndrome compared to controls with dyslexia. Dissertation Abstracts International: Section B: The Sciences and Engineering, Vol 65(11-B), 2005, 6049.

With the proper help, children with dyslexia can learn how to read and spell. The primary intervention is evidence-based multi-sensory reading instruction, most notably Orton-Gillingham Instruction (OGI) or a reading program based on the principles of OGI. This instruction can be received through Special Education services and it is also provided by private reading specialists.

In addition, children with dyslexia can qualify for a range of classroom and test modifications and accommodations, including: test directions or the entire test read, extended time on tests, spelling requirements waived, books on tape, and others.