What Is Dyslexia and How Is It Actually Diagnosed?

By Dr. Tyler Gerdin, PsyD, ABPP | Gerdin Psychological Services

Reading should be the kind of thing that gets easier with practice. For most kids, that’s exactly what happens: a slow, sometimes effortful start in kindergarten and first grade, followed by a gradual smoothing out as decoding becomes automatic and reading becomes a tool rather than the task itself.

Why Dyslexia Is Often Missed

For children with dyslexia, that smoothing out doesn’t come. The words stay slow. The sounding out stays labored. Spelling remains unpredictable no matter how many times the same word is practiced. And because the child is often clearly intelligent, curious, articulate, full of ideas, the gap between their evident capability and their reading performance becomes increasingly confusing to everyone around them, including the child.

Dyslexia is the most common learning disability. It is also among the most misunderstood. And because it’s misunderstood, it’s frequently either missed entirely or identified far later than it should be, long after a child has accumulated years of struggle, frustration, and often a quiet conviction that they must be the problem.

They are not the problem. Their brain processes language differently. And that difference is diagnosable, documented in decades of neuroscientific research, and highly responsive to the right intervention, especially when caught early.

What Dyslexia Actually Is and How the Brain Processes Reading Differently

Dyslexia is a neurodevelopmental, brain based learning disability characterized by persistent difficulties with accurate and fluent word reading and spelling, difficulties that are unexpected given a child’s other abilities and the quality of instruction they’ve received (Snowling et al., 2020; Sanfilippo et al., 2019).

The core of dyslexia is phonological: a weakness in the brain’s ability to process the sound structure of language. Words are made of sounds, phonemes, and reading an alphabetic language like English requires mapping those sounds onto letters and letter combinations. For most people, this mapping becomes automatic with practice. For people with dyslexia, it remains effortful, unreliable, and slow, because the underlying phonological processing system doesn’t operate the same way (Carroll et al., 2025; Adlof & Hogan, 2018).

This is worth emphasizing because it explains why dyslexia isn’t simply “reading slowly” or “reversing letters,” both common misconceptions. Letter reversals are developmentally normal into early elementary school and are not a defining feature of dyslexia. What defines dyslexia is the persistent struggle to decode words accurately and fluently, to hold sound sequences in working memory, and to learn the correspondences between sounds and spelling patterns that most readers internalize without much conscious effort.

Yale researcher and physician Sally Shaywitz, whose landmark book Overcoming Dyslexia brought this condition to mainstream understanding, describes dyslexia as an “island of weakness in a sea of strengths”: a localized difference in phonological processing that coexists with intact, often exceptional, abilities in reasoning, comprehension, creativity, and big picture thinking. That framing matters clinically and personally. Dyslexia is not a ceiling on a child’s intellectual life. It is a specific obstacle in the path to literacy that can be worked around with the right support.

Signs of Dyslexia in Children by Age

In preschool and kindergarten, the early signs are often phonological before they’re about reading at all. Difficulty learning nursery rhymes, trouble recognizing that words rhyme, slowness in learning letter names and letter sounds, and difficulty breaking words into syllables or individual sounds are all meaningful early indicators. These are the building blocks of reading, and when they’re shaky, the reading process that depends on them will be too.

In early elementary, the pattern shifts toward reading and spelling directly. Labored, slow decoding of words the child should be learning to read automatically. Persistent spelling errors that look phonetically reasonable but are consistently wrong (wuz for was, sed for said). Difficulty reading aloud smoothly. Reluctance to read, particularly in front of others. Significant fatigue after reading tasks that peers seem to handle easily.

In older children and adults, dyslexia often looks different because years of compensatory effort have changed the surface presentation. A smart older student or adult with dyslexia may be a functional reader, slow, but capable, because they’ve learned to use context, prior knowledge, and high verbal reasoning to decode meaning when word level decoding fails. What persists is spelling (almost always), reading fluency and speed (usually), and a reading experience that remains effortful in a way others don’t understand. Research has found that over 81% of university students with dyslexia show deficits in word level reading fluency, and 98% show deficits in rapid automatized naming, even at that level of academic achievement (Saunders et al., 2025). Dyslexia doesn’t disappear with age. It adapts.

What Dyslexia Testing Involves and How the Diagnosis Is Made

Diagnosing dyslexia is not a single test. It’s a clinical process that builds a picture across multiple domains, and the picture has to be coherent to be meaningful.

Documenting the reading and spelling problem directly is the foundation. This means standardized assessment of word reading accuracy and fluency (including both real words and nonsense words that require pure decoding), spelling, and oral reading fluency. Nonsense word reading is particularly diagnostically useful because it bypasses visual word memory: if a child can’t decode wug or prane, they’re not compensating with memorization, and the phonological decoding weakness is visible (Łockiewicz, 2025).

Assessing the underlying phonological processing skills that support reading is the next layer. This typically includes measures of phonological awareness (the ability to manipulate sounds in words), phonological memory (holding sound sequences in mind), and rapid automatized naming (the speed at which a child can name familiar items like letters or colors), all three of which are consistently implicated in dyslexia across the research literature (Carroll et al., 2025; Dorofeeva et al., 2022).

Understanding the broader cognitive and language context matters as well. Dyslexia frequently co-occurs with ADHD, developmental language disorder, and other neurodevelopmental differences, and understanding what else is present shapes intervention planning. A child with dyslexia and ADHD needs something different from a child with dyslexia alone, and a good evaluation doesn’t just confirm the diagnosis; it maps the whole landscape.

Documenting real world impact and response to instruction completes the picture. Current best practice treats persistent word level difficulties plus inadequate response to high quality, evidence based reading instruction as the strongest combined evidence for a dyslexia diagnosis (Miciak & Fletcher, 2020). A child who is struggling despite good teaching is showing something neurobiologically real, not a gap that more effort will close.

Why Early Dyslexia Diagnosis Changes Outcomes

The research on early intervention for dyslexia is among the most optimistic in all of developmental psychology, but it comes with an important caveat: the window matters.

Intensive, structured, phonics based reading instruction (programs built on what’s called the Orton Gillingham approach and its derivatives) is highly effective for children with dyslexia, particularly in the early elementary years when the reading system is still being built. The same intervention delivered later is still helpful, but the gains are harder to achieve and the automaticity is harder to develop (Gersten et al., 2005; Lefèvre et al., 2023).

This is why pediatricians, the American Academy of Pediatrics, and literacy researchers all now emphasize early screening, not waiting for a child to fail sufficiently before investigating whether something is wrong. Early phonological awareness skills in preschool and kindergarten can reliably flag children at elevated risk for dyslexia, often before reading instruction has even begun (Sanfilippo et al., 2019). Getting ahead of the struggle, rather than responding to it after it has already shaped how a child sees themselves as a learner, is the clinical goal.

What a Dyslexia Diagnosis Means for Accommodations and Support

A dyslexia diagnosis is not just a label. It is documentation, formal, legally recognized documentation, that a child has a specific learning disability that qualifies them for accommodations and support under IDEA and Section 504. Extended time. Alternative testing formats. Audiobooks alongside print. Access to assistive technology. These are not crutches; they are tools that level the playing field for a brain that is doing real cognitive work to accomplish what other brains do automatically.

A diagnosis is also, for many children and families, a relief. Not because being diagnosed with a learning disability is pleasant, but because it replaces the narrative of “something is wrong with me” with something more accurate: “my brain works differently, and here’s how we work with that.”

Dyslexia Testing in Spokane for Children and Adults

If your child is struggling with reading despite good instruction and effort, or if you’re an adult who has always suspected that reading and spelling have been harder for you than they should be, a comprehensive evaluation is the clearest path to an answer worth acting on.

At Gerdin Psychological Services, psychoeducational evaluations for children and adults include the full battery of assessment needed to diagnose dyslexia and map any co-occurring conditions. Reach out at drgerdin@gerdinpsych.com or 509-676-4313.

Dr. Tyler Gerdin, PsyD, ABPP is a board certified clinical psychologist in Spokane, Washington, specializing in psychological and neuropsychological assessment for neurodivergent teens and adults.