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Expressive Phonological Impairment and the Development of Literacy

Expressive Phonological Impairment and the Development of Literacy
Margot E. Kelman, PhD, CCC-SLP
July 9, 2007

Issues in Published Studies
It is widely acknowledged that learning to read depends on phonological skills (Carroll & Snowling, 2004; Goswami & Bryant, 1990); therefore, children who have phonologically based speech impairments are vulnerable to reading difficulties. There is a large body of research indicating that children with speech and language difficulties are at risk for later associated literacy problems (Bird, Bishop, & Freeman, 1995; Bishop & Adams, 1990; Catts, 1993; Catts, Fey, Zhang, & Tomblin, 2002; Snowling, Bishop, & Stothard, 2000; Stackhouse, 2000); however, most of the research in this area has focused on children with language impairment or those with speech and language deficits. Only a limited number of studies have examined the relationship between phonological deficits and reading skills.

Expressive phonological impairment (EPI), a speech sound disorder characterized by phonologically based (rather than phonetic-/motoric-based) speech errors (Hodson, 2007), is used to describe children with highly unintelligible speech in the moderate-to-severe range. EPI refers to an impaired system of phonemes and phoneme patterns that exist within the context of spoken language. Unlike an articulation disorder that represents difficulties with the production of individual speech sounds (i.e., phonemes), a phonological impairment is characterized by phonological deviations (e.g., stopping, cluster reduction) that apply to an entire class of sounds. EPI may exist in the absence of other significant language impairment, although other language areas such as morphology, syntax, or semantics can be affected. In contrast, an articulation disorder does not usually impact other areas of language development.

Children often receive intervention services to address a phonological impairment. Although intervention services may resolve their phonologically based speech errors, some children with EPI exhibit persistent difficulties with the acquisition of reading skills (Gillon, 2002). In particular, children with expressive phonological deficits may experience difficulties in the areas of phonological awareness ability and spelling. Phonological awareness (i.e., the explicit knowledge of the sound structure of words) has consistently proven to be a crucial factor in early literacy development (Gillon, 2005). Phonological awareness requires an understanding of the relationship between letters or graphemes of printed words and the phonemes of spoken words. To decode words, children must translate a written or orthographic representation of a word into the corresponding phonological representation of the word. Early spelling development also requires an understanding of the association between a word's orthographic and phonological representation (Treiman, Sotak, & Bowman, 2001). Children with phonologically based speech errors often lack a strong foundation for mapping between these orthographic and phonological representations (Hulme et al., 2002). These inadequate abilities are likely to continue throughout the school years unless they are addressed.

Some studies have examined the relationship between EPI and reading skills; however, differing conclusions have resulted. A few factors appear to account for such outcomes. These factors include the terminology used, the severity of the participant population, and the manner in which severity is assessed.


There is variability in the terminology used to identify the participant population in studies of EPI. For example, the term "language disordered" has been used interchangeably with "phonologically disordered." In some cases, the target group is language impaired with no phonological deficits; in other research the participants demonstrate both speech and language deficits but are only identified as speech impaired. Some of the research is unclear whether the children are solely phonologically impaired or if other deficits are present. In studies where children are speech and language impaired, it is nearly impossible to disentangle the effects of poor speech from poor language. Some studies provide no information about the participant's deficit area(s), making it impossible to assess the relationship of the speech deficit to literacy skills. Outcomes have been variable because the participant population is not always thoroughly identified. This inconsistency in terminology reduces the ability for future researchers to replicate the studies and make predictions and/or generalizations about outcomes.


Studies show considerable variation in the range of severity of the sample populations. Some studies include children who are mildly speech impaired while others have children who exhibit moderate-to-severe deficits in phonological skills. Some studies report the severity of the population while others do not. The variability in severity of EPI results in differing outcomes in studies. For example, some studies that include children in the mild range found no correlation between speech deficits and reading ability.

margot e kelman

Margot E. Kelman, PhD, CCC-SLP

Margot Kelman, Ph.D., CCC-SLP is a speech-language pathologist in private practice and clinical supervisor at Wichita State University. Her interests are in early childhood speech, language, and literacy development. Dr. Kelman currently supervises the Toddler Emergent Language and Literacy Playgroup at Wichita State University. 

There are no affiliations or financial interests in corporate organizations with commercial products related to this presentation.

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