A Synthesis of Research on Reading from the National Institute of Child Health and Human Development

Developing a New Understanding of Reading Difficulties

Much of the recent NICHD research has focused on identifying the nature of reading disabilities and the causes. Using modern neuroimaging technology, medical researchers have identified a unique signature on the brain scans of persons with reading problems. These unique brain scans seem to reflect an inability to work with phonemes in the language. This lack of phonemic awareness seems to be a major obstacle to reading acquisition. Children who are not phonemically aware are not able to segment words and syllables into phonemes. Consequently, they do not develop the ability to decode single words accurately and fluently, an inability that is the distinguishing characteristic of persons with reading disabilities.

About 40% of the population have reading problems severe enough to hinder their enjoyment of reading. These problems are generally not developmental and do not diminish over time, but persist into adulthood without appropriate intervention. Because the percentage is so large, an arbitrary cutoff point of 20% was selected for the purpose of labelling children as disabled in basic reading skills. The difference between a child who has a learning disability in reading and a child who is simply a poor reader is only a difference in the severity of the problem.

The most reliable indicator of a reading disability is an inability to decode single words. Lyon (1994, 1995a) suggests that the best way to determine if this inability is “unexpected” is to compare the performance of a child with that of other children his or her age and / or compare reading ability to academic performance in other domains (e.g., listening comprehension, verbal expression, mathematics, written expression). The definition suggests that traditional methods for identifying a reading disability, such as looking for an IQ-achievement discrepancy, are not as reliable (Lyon, 1994; Lyon, 1995a).

Phonological processing is the primary ability area where children with reading disabilities differ from other children. It does not seem to matter whether the children have an IQ-achievement discrepancy in reading or not. Phonological processing encompasses at least three different components. Each component and a sample assessment are described in Table 2.

Table 2. Three important components of phonological processing and sample assessments.

Of these three major phonological processing skills, phonological awareness appears to be the most prevalent linguistic deficit in disabled readers.