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Different Kinds of Dyslexia and
Co-Occurring Diagnoses

What is Dyslexia? 

  • Dyslexia is a language-based condition that interferes with the ability to convert written words into spoken words, or to “decode” them.
  • Being dyslexic has nothing to do with eyesight or intelligence. 
  • Dyslexics have average to very high intelligence. They are highly creative, intuitive and gifted.
  • Dyslexics have a hard time reading and writing.
  • Dyslexia is not just the popular misconception about “reversing letters.” That is only one of many symptoms which leads to reading and writing difficulties. 
  • Dyslexia is not a learning disability, it is a learning difference. 
  • Dyslexia cannot be “grown out of.” Dyslexic kids need to be taught in the best ways to help them maximize what they can do.
  • There are emotional impacts of having dyslexia in the conventional educational system and the workplace. Dyslexics excel when they have support. They suffer when they don't. Learn more HERE.
  • Recognizing and supporting dyslexics is important because dyslexics are 20% of the population, that's 1 in 5 people, according to the International Dyslexic Association and Sally Shaywitz. By comparison ASD is 1% and ADHD is 7% of the population and they often have more advocacy. For dyslexics in school, the workplace, therapy settings, and life, they are often an invisible population who deserves support so they can feel proud and identify and use their amazing gifts of dyslexia.

What’s Going On in the Left Brain of the Dyslexic?

Dyslexics are highly creative, intuitive and gifted, primarily due to the neural towers in their brain being spaced farther apart than the non-dyslexic population. This results in the neural signals having to travel farther and this is what results in their great big picture recognition and pattern recognition skills, their narrative abilities, their dynamic thinking and ability to accurately predict outcomes, their empathy, intuition, creativity and other gifts—learn more about their incredible right brain strengths here: DYSLEXIC STRENGTHS. And more about how their brains work here: HOW THE DYSLEXIC BRAIN WORKS

Concurrently with the neural towers in their whole brain being more widely spaced, the left brain areas responsible for reading and writing don’t function in the same way as nondyslexics resulting in difficulty reading and writing. 

It is in the left brain that words are “decoded” or read silently or aloud, and “encoded” or written. Dyslexics don’t use their left brain in the same way, and thus have difficulty in phonetic decoding—turning symbols into a sound in the brain and then stringing them together to compose a word, and in encoding or writing. 

  • DECODING (happens in the left brain) is turning phonetic symbols into a sound in the brain then stringing them together to compose a word. These are dyslexic challenges.
  • ENCODING (happens in the left brain) is writing. These are the challenges of dysgraphia, which 30% of dyslexics have.

Depending on the intensity of their dyslexia, dyslexics often reach a ceiling in their ability to read and with their handwriting. For example, some people with dyslexia may always have handwriting that is almost illegible even to themselves. Some successful dyslexics have never been able to read more than a book or two in their lives. However, these same people may become wonderful writers and produce great books, like naturalist and artist Jack Laws who has recently published the wonderful Laws Field Guide to The Sierra Nevada.

Distinguishing Between Causes of Dyslexia

  • Primary Dyslexia. Dyslexia runs in families. Primary dyslexia is a genetically inherited condition. Some estimates say 40% to 60% of children with dyslexic parents will also be dyslexic. This kind of dyslexia is present from birth. It is more common in males than females. 
  • Secondary Dyslexia results from problems with brain development during the early stages of fetal development. This kind of dyslexia is present from birth.
  • Developmental Dyslexia is another name for Primary and Secondary dyslexia. It refers to intelligent, motivated, kids and adults who have unexpected difficulties with accurate and fluent reading. This term is used to distinguish them from people who have reading issues due to a severe head injury/Acquired Dyslexia. 
  • Acquired Dyslexia, also called Trauma Dyslexia, Deep Dyslexia or Alexia is used to describe people who have had traumatic brain injury or disease affecting the left hemisphere which results in them developing severe language processing difficulties and dyslexia. The other gifts of dyslexia are absent. 

Kinds of Dyslexia 
Based on Symptoms

Phonological Dyslexia 

Also call dysphonetic dyslexia and auditory dyslexia

From Neurohealth:Phonics is the ability to break words down into individual sounds. People with this kind of dyslexia can often process and understand whole words, but not the individual sounds that make them up. They have trouble decoding and sounding out words.

From Edublox: “This type of dyslexia includes trouble breaking words into syllables and smaller sound units called phonemes. For example, if you say a word out loud to a child with weak phonemic skills, he can hear the word just fine and repeat it back to you. But he’ll have trouble telling you how to split it apart into the different sounds that make up this word. Difficulties in this area can make it challenging for readers to match phonemes (the sound units) with their written symbols (graphemes), which makes it hard to sound out or “decode” words.”

Surface Dyslexia 

Also called dyseidetic dyslexia, visual dyslexia, and orthographic dyslexia.

From Neurohealth:People with surface dyslexia have trouble recognizing familiar words on the page and matching printed words to their sounds. This makes it hard for them to memorize and remember words, even ones they’ve already learned.” 

From Edublox: “This type of dyslexia refers to kids who struggle with reading because they can’t recognize words by sight. Sight-reading is an essential skill for a couple of reasons. One is that some words have tricky spellings. For example, words like weight and debt can’t be sounded out — readers need to memorize them. The other reason has to do with reading fluency. To read quickly and accurately, kids need to recognize many common words at a glance — without sounding them out.” 

Rapid Naming Dyslexia

RAN stands for Rapid Automatized Naming and refers to the speed with which a person can retrieve names of symbols (letters, number, colors, or pictured objects) from long term memory. A person with Rapid Naming Dyslexia has trouble naming letters, colors, and numbers quickly and involves difficulties with both reading pace and language processing.

Double Deficit Dyslexia 

This refers to people who have both Phonological Dyslexia (breaking words into syllables and smaller units of sounds called phonemes) and Rapid Naming Dyslexia (trouble naming letters, colors, and numbers quickly). It is regarded as the most severe type of dyslexia.

Links for more on the Different Types of Dyslexia:     Edublox     Neurohealth     The Reading Well

The following is a list 
of Learning Disorders 
which are NOT dyslexia. 
However Dyslexia may CO-OCCUR 
with one or more of 
these learning disorders:


  • Attention Deficit Hyperactivity Disorder. An ongoing pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
  • It is estimated that 30% of dyslexics also have ADHD—from The International Dyslexia Association


  • Difficulties in arithmetic and mathematics. 
  • It is estimated that 40% of dyslexics also have dyscalculia—from Exceptional Individuals


  • A specific set of writing challenges that impacts handwriting and spelling—“encoding” words.
    It is estimated that 30% of dyslexics also have dysgraphia—from NIH


  • Dyspraxia or “clumsy child syndrome”—a neurodevelopmental coordination disorder affecting verbal, oral and/or motor coordination causing kids to struggle with speech or with fine motor skills like handwriting or tying shoelaces. 
  • It is estimated that 52% of kids with dyslexia also have some feature of dyspraxia—from Foundation for People with Disabilities.

Auditory Processing Disorder or APD

  • Auditory Processing Disorder. It’s about how the brain processes sound and heard language.  Where dyslexia is a language-based condition where the individual has difficulty processing visual language-based stimuli, someone with Auditory Processing Disorder has difficulty processing heard stimuli—difficulty accurately and efficiently processing sounds and language. These individuals are unable to hear words correctly. There are several different kinds of APD.
  • It is estimated that up to 70% of dyslexics also have some kind (but not necessary all kinds) of APD.
  • Succeed with Dyslexia explains the difference between dyslexia and APD this way: “The two conditions are quite different in their effects: APD is a difference in how the brain processes sounds and heard language, whereas dyslexia is widely agreed to be a language-based learning disability often associated with weaker reading skills, poor spelling, slower reading processing and character confusion when unsupported. There are a number of different types of APD, but not all seem to occur with the same frequency in people who have dyslexia: most people with dyslexia and APD will demonstrate weaknesses in temporal sequencing of information, auditory figure ground problems, and interautal asymmetry in competition. So that’s ‘remembering what order you heard a list or some instructions in’, ‘the ability to pick out sounds from a noisy or disruptive audio backdrop’ and ‘differences in assessed listening performance between each ear’ – although it is very possible for different forms of APD to exist in people with dyslexia too. The combined effect of APD and dyslexia can mean that it’s difficult for somebody to take in information in both of these forms.”

Visual Processing Disorder is 
NOT Dyslexia, NOT Dysgraphia, NOT ADHD

Visual Processing Disorder can interrupt an individual’s ability to understand and navigate written symbols, which may cause problems with math and reading. They’re not due to vision problems or any issues with the eyes, but rather with how the brain interprets visual information.

On the other hand, Dyslexia is a separate condition that makes it challenging to break spoken language down into its component parts. This makes reading and spelling difficult. While the two conditions can look similar, they have different causes and thus children and adults who have one and not the other will require a different set of strategies and accommodations.

Unfortunately, Visual Processing Disorder is not well recognized by schools and testing for this is often overlooked. Visual Processing Disorder is often mistaken for dyslexia (VPD students also have trouble with reading, writing and spelling), dysgraphia (VPD students also have trouble with math and penmanship) and ADHD (VPD students’ poor visual processing makes their world overwhelming and they have trouble remaining attentive) and the wrong interventions are used.

Learn more about Visual Processing Disorder at Building Better Brains.

The Dyslexic Mind Strengths Are Amazing