Dyslexia is a specific learning disability that affects reading, writing, and spelling skills. It is neurobiological, stemming from differences in brain structure and function. Individuals with dyslexia often experience difficulties with accurate word recognition and decoding, impacting language processing skills like phonological awareness. Dyslexia exists on a spectrum, with varying degrees of severity, and its effects can extend beyond literacy to areas such as organization and memory.
Precursors to Formal Recognition
Before formal medical recognition, historical accounts show individuals struggled with reading. For example, in the 16th century, Saint Teresa of Ávila reportedly lost the ability to recognize words. In 1676, Johannes Schmidt documented a case of a person unable to read for non-optical reasons. These early observations highlighted reading impairment independent of general cognitive skills or vision, laying groundwork for later investigations.
The Initial Medical Descriptions
The formal medical exploration of reading difficulties began in the late 19th century. In 1877, German physician Adolph Kussmaul described “Wortblindheit,” or “word blindness.” He observed this in adult patients who had lost the ability to comprehend written words, often due to brain injury, despite intact sight, intellect, and speech. Kussmaul differentiated this from aphasia, a condition where patients struggled with language comprehension due to brain injury. He emphasized that word blindness could exist as an isolated symptom, where the individual could see letters distinctly but was unable to interpret their meaning as written language.
Kussmaul’s descriptions were not limited to acquired conditions; he also identified similar difficulties in individuals who had never learned to read, setting the stage for the distinction between acquired and developmental reading impairments. This early medical documentation established that a severe inability to read could be a specific medical concern, unrelated to general intelligence. Kussmaul’s work provided an initial framework for understanding reading disabilities as a distinct field of study.
Pioneering Investigations and Naming
The concept of “word blindness” continued to evolve with further investigations and the introduction of a new term. In 1887, Rudolf Berlin, a German ophthalmologist, coined the term “dyslexia” from Greek roots meaning “difficulty with words.” Berlin initially used this term to describe cases of partial reading loss in adult patients who had experienced brain lesions, which is now referred to as acquired dyslexia.
Independent observations by British physicians further shaped the understanding of developmental reading difficulties. In 1896, W. Pringle Morgan, a general practitioner, published a description of a 14-year-old boy named Percy who, despite being bright and intelligent, had a profound inability to learn to read. Morgan termed this condition “congenital word blindness,” postulating it was due to a developmental defect in the brain rather than injury. This focused attention on reading disabilities present from childhood.
Following Morgan, Scottish ophthalmologist James Hinshelwood conducted extensive studies on “congenital word blindness” in the early 1900s. Hinshelwood described cases of children who struggled significantly with reading, often exhibiting letter reversals and spelling problems, despite normal intelligence. He suggested that this condition was neurological, specifically attributing it to a developmental defect in the left angular gyrus, a brain region involved in processing visual memories of words and letters. Hinshelwood’s work, along with Morgan’s, solidified the idea of a specific, developmental reading difficulty distinct from acquired brain injury.
Evolving Understanding in Early Research
Research into dyslexia began to refine its understanding, shifting focus from purely visual deficits to broader language processing issues. American neurologist Samuel T. Orton, active in the 1920s and 1930s, played an important role in this shift. Orton challenged the prevailing “word blindness” theory, which often implied a visual problem. He proposed that specific reading difficulties stemmed from a neurological basis, particularly related to issues with language processing and the organization of brain hemispheres.
Orton’s studies with over 1,000 children revealed that many struggling readers, despite having average or above-average IQs, exhibited difficulties such as letter reversals and transpositions. He introduced the term “strephosymbolia,” meaning “twisted symbols,” to describe this confusion in visual symbols. While his specific theories on hemispheric dominance were later updated, Orton’s emphasis on language processing and the brain’s role in reading was significant.
His work moved the field beyond a sole focus on visual perception, paving the way for modern research on the phonological components of language difficulties in dyslexia. Orton’s insights also led to the development of multisensory teaching approaches, which integrate auditory, visual, and kinesthetic learning channels, still influencing educational strategies for dyslexia today. This period marked a transition towards a more comprehensive, neurologically-informed view of reading disabilities.