In the late 1800’s, Dyslexia was known as “word blindness”. German neurologist, Adolf Kussmaul, was the first to recognise the condition and explained is as “complete text blindness. Although intellect and the power of sight and speech are intact”. Kussmaul worked with children and noted that although they displayed extreme reading difficulties, they were otherwise very able.
It was in the year 1887 that the term ‘Dyslexia’ was penned by German ophthalmologist Rudolf Berlin and was used then, as it is now, to describe the condition (meaning ‘difficulty with words’). He coined it from the Greek words ‘dys’ meaning ill or difficult and ‘lexis’ meaning word.
Berlin observed the difficulties faced by some of his adult patients with brain lesions who had full command over verbal communications but had lost the ability to read.
The first academic paper on the condition was published in the British Medical Journal in 1896 by a physician, William Pringle Morgan; his research focused not only on word-blindness as an isolated symptom but broadened accounts of the condition. Other Britons including James Hinshelwood, an ophthalmologist and James Kerr, a council medical officer, also continued to research further into Dyslexia.
The outcome of their research weakened the explanatory power of brain injury or disease as Dyslexia’s cause, which had previously been favoured, setting up a distinction between acquired and congenital/developmental Dyslexia; the former occurring suddenly during adulthood, the latter present at birth.
Acquired and developmental Dyslexia
Research continued into the 1900’s with Hinshelwood attempting to identify both conditions. He concluded that acquired Dyslexia is a neurological condition owing to brain injury and congenital Dyslexia is hereditary. He attributed congenital/developmental Dyslexia to a lesion in the left angular gyrus of the brain, which impaired the ability to store and remember visual memories for letters and words. It was in the 1900’s that it was suggested Dyslexia was more common in boys.
Alongside Hinshelwood, Samuel Torrey Orton, a neurologist, and neuropathologist in the USA was also continuing research on Dyslexia. Orton advocated the term strephosymbolia (twisted symbols) which explained that the problem was not one of word-blindness per se, but that visual impressions were ‘distorted’ in the perceptual processing of letters and words.
It was Orton’s developments within the area which caused the move of Dyslexia from medical to educational ownership. This led to it being ‘treated’ by educational development rather than medical intervention.
Interest in Dyslexia waned for several years but came back in the 1960s with several theories of cognitive development, psychologists were now leading the further research into Dyslexia. In 1972, researcher Sandhya Naidoo published a book called Specific Dyslexia which was one of the first major studies of Dyslexia, alongside Critchley’s published a book called The Dyslexic Child.
Neurologist Macdonald Critchley and psychologist Tim Miles opened The Word Blindness Centre in 1962. The centre brought together many researchers who had worked with dyslexic individuals. Unfortunately, this closed its doors in the early 1970’s. This closure led to several organisations dedicated to Dyslexia were founded. They included the Helen Arkell Dyslexia Centre (1971), the Dyslexia Clinic at Barts Hospital (1971), the British Dyslexia Association (1972), the Dyslexia Institute (1972), the Language Development Unit at Aston University (1973) and the Bangor Dyslexia Unit (1977), amongst others. Some of these remain in operation today, providing a source of support for children, their parents, and adults with Dyslexia, as well as professionals working in the area. These organisations worked alongside other researchers, campaigners and practitioners in psychology and education.
The development of neuroimaging technologies during the 1980s and 1990s enabled Dyslexia research to make significant advances. Brain imaging studies have also described the irregular patterns of neuronal activation associated with reading and phonological processing in adults with developmental Dyslexia.
In the early 2000’s, researchers suggested that Dyslexia may be characterised in childhood by disruptions in the neural bases of both phonological and orthographic processes important for reading. It was also reported that both visual motion sensitivity and auditory sensitivity to frequency differences were predictors of children’s literacy skills and their orthographic and phonological skills.
As of 2003, the relation between the brain and Dyslexia was generally focused on some form of defective or delayed brain maturation; in 2008 it was suggested that Dyslexia may result from distinct cognitive impairments. More recently, genetic research has provided increasing evidence supporting a genetic origin of Dyslexia.
Scientists have identified several specific genes that are strongly associated with Dyslexia, making those who carry them prone to developing it. Thus, 50% of those with a sibling or parent with Dyslexia will receive the diagnosis themselves. Equally, new research in 2020 corroborates the strong inheritability of Dyslexia.
However, it is important to point out that there is no such thing as “the Dyslexia gene” that determines a child’s fate.
Genetic factors are just one type of underlying factor that can lead to Dyslexia. The multiple deficit approach to Dyslexia is now considered the most accurate way to understand causation. In addition to genetic factors, Dyslexia is a result of brain-level differences, perceptual/cognitive-level differences, and environmental factors.