- 5 –10% of the PDD individuals are hyperlexic.
- Hyperlexia has been observed in individuals with Turner Syndrome, Tourette Syndrome, and various forms of mental retardation (Fontenelle & Alacron, 1982; Mehegan & Dreifuss, 1972; Worthy & Invernizzi, 1995). 
- A lack of agreement on hyperlexia as a subtype or a symptom of developmental dyslexia, SLI, or PDD, etc.


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The word hyperlexia was initially coined based on a study focusing on children primarily with various forms of ‘cerebral dysfunction’ by Silberberg and Silberberg (1967).


- Reference: Silberberg, N.E., & Silberberg, M.C. (1967). Hyperlexia: Specific word recognition skills in young children. Exceptional Child, 34, 41–42.

How Should Hyperlexia Be Categorized (a symptom, a syndrome, or a normal variant)?

Grigorenko, E. L., Klin, A., & Volkmar, F. (2003). Annotation: Hyperlexia: Disability or superability? Journal of Child Psychology and Psychiatry, 44(8), 1079–1091.

Grigorenko et al., 2003

Hyperlexia appears to be a variant of the semantic-pragmatic syndrome of developmental language disorder as described in the Child Neurology Nosology rather than a variant of developmental dyslexia. 
 - Written language limitation (i.e., problems of comprehending written material).
- Spoken language limitation (i.e., problems with comprehending oral material).


Hyperlexia as a Subtype of Language Impairment 

Some researchers view hyperlexia as a type of preconscious reading (Penning- ton et al, 1987). Hyperlexic children can read single words without comprehension. Children with such reading skills may be perceived as part of the high-IQ population. 

Hyperlexia as a Variant of Typical Development 

- Hyperlexia has been referred to as a subtype of developmental dyslexia (DD), specific language impairment (SLI), reading comprehension disorder, and pervasive developmental disorders (PDD). 
- In some cases, hyperlexia might be an early indicator of a developmental disability. Although hyperlexia and dyslexia are two extremes, individuals from dyslexic families also have family members who are hyperlexic.


Hyperlexia as a Variant of Atypical Development 

Dyslexia refers to reading at a level lower than general cognitive skills. However, hyperlexia indicates a higher word recognition level than general cognitive skills. 

Hyperlexia as a subtype of dyslexia 

Discrepancy between single-word reading and word comprehension: With advanced decoding skills but struggle with comprehending meaning and understanding sentences.

Findings:
- Comprehension disorder becomes diagnosable by middle school.
- Distinctive differences in neuropsychological profile between children with comprehension difficulties and children with developmental dyslexia. 
- The discrepancy between single-word recognition and vocabulary or single-word recognition and reading comprehension, or comprehension deficit is observed comparably as often as developmental dyslexia in the general population. 


Hyperlexia as a Central Feature of Reading Comprehension Disorder 

Hyperlexia is defined as an advanced level of word recognition skills and general cognitive functioning of an individual. It tends to happen in young children. 

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