When Dyslexia Was Called 'Word Blindness'

October is Dyslexia Awareness Month, making it a good time to revisit an intriguing chapter in the history of language and the brain: how the medical profession came to understand dyslexia. What began as a puzzling disconnect between vision and reading would eventually reveal that reading is far more than simply seeing words on a page.

A Problem With Written Words, Not Eyes

In the 19th century, doctors encountered people who could speak, write, and understand language normally, yet struggled to read. In the 1870s, German physician Adolf Kussmaul gave this puzzling condition an evocative name: Wortblindheit, or “word blindness” (Stollznow, 2026).

However, the label was misleading. These people were not literally blind, and their eyesight was often perfectly normal. Their difficulty was with the written word. The mystery was how someone could see a word clearly yet be unable to make sense of it.

Kussmaul’s observations influenced Rudolf Berlin, a German ophthalmologist who studied patients struggling to read despite having normal vision. In 1877, Berlin coined a new term for the condition: dyslexia, from Greek roots meaning “difficulty with words.” The new term shifted attention away from blindness and toward the relationship between the brain and written language.

A Bright Boy Who Couldn’t Read

Let’s look at the case of Percy, a 14-year-old English boy described by physician William Pringle Morgan in 1896. Percy was, Morgan observed, “bright and intelligent, quick at games, and in no way inferior to others of his age” (Kirby & Snowling, 2022). Yet he could not learn to read. Percy’s spelling was particularly inventive. He wrote “scone” for song, “scojock” for subject, “wiehout” for without, and even misspelled his own name as “Precy.”

Morgan suspected that Percy’s difficulty was a congenital defect. In modern terms, developmental dyslexia usually begins in childhood and has a strong genetic component. It can run in families, although having a parent with dyslexia does not mean a child will necessarily develop it.

What stands out about Percy’s story is how clearly Morgan distinguished his reading difficulty from his abilities in other areas. Percy’s problem was not a lack of capacity or effort, but the specific challenge of making sense of written language. More than a century later, that distinction remains very important. Dyslexia is a difficulty with reading and language processing, not a measure of intelligence.

When Reading Happens Differently

Today, researchers understand dyslexia as involving differences in how the brain processes written language, particularly the processing of sounds. One core difficulty is phonological awareness: recognizing, separating, and manipulating the sounds that make up words, and connecting those sounds with letters. That can make reading surprisingly effortful. A person with dyslexia may read slowly, misread words, struggle with spelling, or have difficulty distinguishing letters and sounds. Words may seem to blur together, and reading silently can be especially challenging.

But dyslexia does not mean that someone has trouble understanding language. In fact, some people with dyslexia find that they understand and remember information more easily when they hear it rather than read it. This is one reason audiobooks, text-to-speech software, and other tools can make such a difference.

Brain imaging studies have also found differences in the neural networks involved in reading. Typical readers rely heavily on a network of language-related regions, particularly in the left hemisphere. In people with dyslexia, these networks can function differently, with changes in brain activity and connectivity that may make reading more laborious (Carneiro et al., 2024).

Seeing Isn’t the Same as Reading

Dyslexia is surprisingly common. Estimates vary considerably depending on how dyslexia is defined and identified. One recent study of children in elementary school found a pooled prevalence of about 7 percent worldwide (Yang et al., 2022). Some estimates are even higher.

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So “word blindness” was not quite the right description. People with dyslexia are not blind to words. Their eyes can see them. Their brains process the relationship between letters, sounds, and language differently.

There is another condition called “word blindness” too, a term once used for acquired difficulties with reading, particularly after brain injury. The medical term alexia is now more commonly used for this condition.

Yet the outdated phrase captures something worth remembering. For someone struggling to read, words can become strangely inaccessible, even when everything else about their vision is working perfectly. The words are there, but seeing them is not the same as reading them.

And perhaps that is what the history of dyslexia teaches us most clearly: The same page can present a very different experience to different brains. A difficulty that once seemed mysterious is now helping us understand just how much happens between seeing a word and making sense of it.