It would appear that reading difficulties for children fall into two broad categories: developmental dyslexia – extreme decoding problems when reading instruction begins, and hyperlexia (also developmental) characterised by relatively strong word reading skills but lower reading comprehension. Although the research base in both areas is not substantial, the vast majority and highest profile area is dyslexia (more here).
To summarise, the dominant concept of developmental dyslexia is that it is a heritable code-based word reading disorder that stems from a core deficit in phonological processing and occurs on a wide continuum from mild spelling problems to severe reading impairment with the severity of the symptoms not correlated with IQ. Dyslexic readers appear to exhibit some neurobiological differences when compared to typical readers particularly in patterns of activation during word reading. Nevertheless, dyslexic readers require the same code knowledge and instruction as typical readers and may take longer to develop orthographic processing (in other words they need to be taught to read in the same manner that all children should be taught, through a code-based approach). Early diagnosis and intervention with a focus on this bottleneck, with patience and persistence (Kucan and Palincsar, 2011) without ignoring the development of thinking and reasoning appears to normalise much of the necessary neurological activation of the left temporal region (Shaywitz et al., 2004) required for effective word reading.
Between 10 and 25 % of children with reading disorders can read single words accurately but have problems understanding the meaning of text (Aaron et al., 1999) – termed hyperlexia. Hyperlexics have strong decoding and word reading skills, but weak comprehension and these problems arise during listening as well as reading. (Nation et al., 2004). There continues to be debate as to whether hyperlexia is considered a deficit model (poor comprehension) or a super-ability (high word reading ability). However, the definition of age-appropriate word reading, and delayed comprehension is generally accepted. The sources of these comprehension deficits are still under investigation with initial research focusing on readers with lower IQ (Bender, 1955) but more recent research suggesting multiple processing deficits contributing to the comprehension problems experienced both when listening and reading ((Nation, 2005) with a key contributing factor appearing to be deficits in verbal working memory (Nation and Snowling, 1999). In addition to lexical processing and working memory deficits there also appears to be difficulty with discourse level processing resulting in problems drawing inferences from text with ensuing issues developing vocabulary as children mature and are unable to infer meaning of unknown words (Cain et al., 2003). Hyperlexics also struggle to monitor their understanding of text particularly when reading anomalous passages (Oakhill, 1996). Thus, the failure of higher-order discourse processes seem to be the result of underlying weaknesses in semantic and syntactic processes (Perfetti et al., 1996).
Unsurprisingly perhaps, studies have documented higher incidences of hyperlexia in children with low verbal IQ and diagnosed with autism (Grigorenko et al., 2002) and has also been diagnosed in children with Tourette’s and Turner’s syndrome (Temple and Carney, 1996). It is generally considered an independent language-based learning disorder that does not result directly from development social disabilities but may occur with them. However, it should be noted that irrespective of the common association between hyperlexia and autism research reveals very few differences in reading performance between autistic and non-autistic hyperlexic readers (Snow and Frith, 1986). They concluded that hyperlexia was marked by low verbal cognitive ability and NOT the presence or absence of autism. Interestingly, Newman et al. (2007) found hyperlexic autistic children were superior to non-hyperlexic autistic children on phonological processing tasks.
Much of the intervention research on hyperlexia has focused on autistic children with studies suggesting that text related to the interests of the reader improve comprehension (Koenig and Williams, 2017) along with bespoke speech and language development and the use of pictures to illuminate meaning (Murdaugh et al., 2015). Furthermore, with vocabulary often being a proxy for background knowledge (Mancilla-Martinez and McClain, 2020) the development of vocabulary assists comprehension (Stanovich, 1986). The home and school environments are essential for building vocabulary and knowledge and conceptual understanding (Rowe et al., 2014). There is limited research into the effectiveness of technology to develop comprehension for hyperlexic children with some suggestion that eBooks, when supported by parents may be beneficial particularly in respect of vocabulary development (Reich et al., 2016)
There has been some suggestion that the incidence of hyperlexia is higher among children taught through a phonics-based programme (Niensted, 1968). However, as the two competencies of word reading and comprehension do not develop in tandem (Landi and Perfetti, 2007), Rayner et al. (2014) suggest that phonics instruction merely enhances word-decoding skills relative to comprehension. In languages with orthographically transparent writing systems children are often fluent readers by the age of seven and have word reading skills that exceed their comprehension and meaning vocabulary. In other words they can read text aloud that they cannot understand.