Dyslexia is a specific learning disability that originates in the nervous system, characterized by unexpected difficulties with accurate and fluent word recognition. Individuals with the condition often struggle with poor spelling and decoding abilities, though these challenges are separate from general intellectual capacity. Tracing the discovery of this condition involves moving through a history of medical observations, evolving theories, and eventual institutional recognition. This journey reveals how a seemingly isolated reading difficulty transformed into a recognized neurobiological difference.
The First Documented Cases
The first formal descriptions of this specific reading difficulty emerged in the late 19th century from European medical practitioners. In 1877, German neurologist Adolph Kussmaul coined the term Wortblindheit, or “word-blindness,” to describe a condition where a patient could not read written words despite having intact vision and speech capabilities. Kussmaul differentiated this phenomenon from aphasia, the loss of language ability due to brain injury. In 1887, German ophthalmologist Rudolf Berlin first used the term “dyslexia,” meaning “difficulty with words,” to describe the reading challenges he observed.
These initial observations were further refined by British physicians in the 1890s, who began focusing on the developmental, or “congenital,” nature of the condition in children. In 1896, British doctor W. Pringle Morgan published a case study about an intelligent boy who could not learn to read. Scottish ophthalmologist James Hinshelwood dedicated extensive research to “congenital word blindness,” arguing it was a specific, hereditary defect in the brain’s visual memory center for words and letters. These findings established that reading failure could exist in bright children, independent of poor vision or lack of intelligence.
Defining Early Theories
In the early 20th century, the focus shifted from purely medical observations to theories rooted in psychology and neurology. American physician Samuel T. Orton became a central figure. Orton challenged the notion of a localized brain lesion, proposing a theory centered on the brain’s hemispheric organization.
He introduced the term strephosymbolia, meaning “twisted symbols,” to describe the common letter and word reversals he observed. Orton hypothesized that these difficulties stemmed from a failure to establish complete cerebral dominance, where the language-responsible left hemisphere was not fully asserting itself. Although the specific theory of mixed dominance was later revised, it advanced the understanding of dyslexia as a neurobiological disorder. His research was foundational to the development of multisensory teaching principles, later formalized into the Orton-Gillingham instructional method.
Establishment as a Distinct Learning Disability
The mid-20th century marked the formal classification of dyslexia. The term “word-blindness” was gradually replaced by “dyslexia.” A significant turning point occurred in 1968, when the World Federation of Neurology’s Research Group created the first consensus definition of the condition.
This 1968 definition characterized dyslexia as a disorder involving difficulty in learning to read despite adequate intelligence, conventional instruction, and socio-cultural opportunity. By framing the condition as dependent upon “fundamental cognitive disabilities which are frequently of constitutional origin,” this definition solidified the understanding of dyslexia as an inherent difference in brain function. This institutional recognition ensured dyslexia was seen as a specific learning challenge distinct from general intellectual disability, paving the way for specialized educational accommodations and diagnostic criteria used today.