Dyslexia in Children Part 2

Dyslexia in children impacts approximately 1 in every 5 children in American classrooms.

Causes and Types of Dyslexia in Children

Morton J (2004) Understanding Developmental Disorders: A Causal Model Approach. Adapted from M. S. Thambirajah APT 2010;16:299-307

There are several theories about the causes of dyslexia. Morton identified a causal model of developmental disorders, including dyslexia, that integrates three levels of functioning—biological, cognitive, and behavioral—as well as environmental factors. Dyslexia in children clearly has a genetic component and runs in families. Children who have a parent with dyslexia are 40-60% more likely to inherit dyslexia with potentially higher percentages when more family members are also affected. Children who have a parent with dyslexia are 40-60% more likely to inherit dyslexia with potentially higher percentages when more family members are also affected.❞ Research is continuing to provide more information about the chromosomes that might be responsible for inherited dyslexia as well as other conditions, such as attention-deficit disorders, that may coexist with dyslexia. Level of intelligence is not a factor in dyslexia. Although dyslexia occurs across the span of intelligence levels, the majority of children with dyslexia have normal or above average intelligence.

Dyslexia is a neurological disorder that impacts the effective processing of language by the brain. Studies by Shaywitz et al. indicate that three main areas of the brain’s left hemisphere appear to be underutilized in children with dyslexia. These neural networks are: Inferior frontal gyrus (Broca’s area)—articulation and word analysis; Parieto-temporal—word analysis; Occipito-temporal—word formation

Some studies have also indicated that the corpus callosum, the nerve fibers that control communication between the two hemispheres of the brain, may also be associated with reading difficulties. A summary of dyslexia brain research can be found on the International Dyslexia Association website here. It is reasonable to assume that additional brain research will result in a better understanding of the neurological components of dyslexia.

Although a number of causes of dyslexia have been proposed, the largest percentage of children with dyslexia appear to have difficulty with phonological processing abilities. This Core Phonological Deficit theory is currently believed to explain the poor phonemic awareness and inability to master the alphabetic principle experienced by many individuals with dyslexia. Difficulties in phonemic awareness make it challenging for children to match the sounds (phonemes) with the written symbols for those sounds which are letters (graphemes). In phonetic languages such as English, this results in an inability to segment words into individual sounds. The word cat, for example, is made up of three phonemes, /k/ /a/ /t/.

/K/ /A/ /T/

This difficulty with segmenting makes it hard to put phonemes together to accurately decode words in print, /k/ /a/ /t/ = cat.

Another type of dyslexia, referred to as “deep dyslexia”, generally occurs after stroke or other brain injury, and is rarely a cause of dyslexia in children.

Recognizing and Assessing Dyslexia in Children

Although reading is a complex process, if appropriate instruction has occurred, the majority of students will have the basic skills for reading in place by 2nd grade. At this point, students should be able to match the sounds to letters and apply these skills to simple words as well as recognize patterns within words (for example, silent e). When there are difficulties with basic reading skills and when students are guessing or unable to hold on to sight words or avoiding reading, this may indicate a problem with reading.

Beyond 3rd grade, dyslexia in children may be both more obvious and more hidden. This paradox occurs because children are transitioning to silent reading with the expectation that they will obtain information from text that they read to themselves. In many cases, teachers are no longer assessing for decoding ability or fluency and some students will never again have their oral reading skills assessed. For children who are struggling readers, a host of issues accompany this scenario: reading very slowly, skipping words, substituting words, inserting additional words, or guessing words, without anyone realizing that this is occurring.

As the demands of reading increase and students can no longer rely on pictures, they may fall farther and farther behind their peers.❞

Students with dyslexia often don’t have a decoding strategy for unknown words but may become masterful at using context to determine meaning. This can make it difficult for teachers to recognize that a student is struggling to decode or comprehend what they are reading. As the demands of reading increase and students can no longer rely on pictures, they may fall farther and farther behind their peers. In the upper grades, not only does the volume of words increase, but vocabulary becomes more complex. Students are expected to decode words with many syllables, fluently read words that contain prefixes and suffixes and understand the meaning of these new words, and retain subject-specific vocabulary that may not yet be a part of their oral speech (variable, chromosome,

Difficulty with spelling and writing are also possible indications of dyslexia in children. Students who leave out the vowels in words (lv for love, frst for first) or spell phonetically (reesuns for reasons) or continue to have reversals (cardon for carbon) in upper grades are providing clues that must be addressed.

Missing Vowels

Phonetic Spelling


Lv for Love
Frst for First



Students who do not receive targeted intervention are much more likely to have negative academic outcomes and social, emotional, and vocational difficulties continuing into adulthood.

Communication disorders such as stuttering and cluttering, particularly when evidence of reading and writing problems exist, can also indicate dyslexia in children. Cluttering, also known as tachyphemia, is a communication disorder characterized by decreased speech fluency and clarity. Different from stuttering or stammering, children with this speech disorder may be unable to communicate using a normal flow of words or may speak in short sentences. Their speaking may be jumbled or contain unrelated words making it difficult for others to understand them.

The presence of one or more of these symptoms, with or without a family history of dyslexia, should trigger a more systematic assessment of reading skills to include phonemic awareness, decoding, and oral reading fluency. These assessments can be conducted in the classroom to develop an understanding of a student’s language strengths and weaknesses. When students are unable to meet reading and writing benchmarks, even with adequate instruction, a formal evaluation for reading disabilities must be the next step.

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