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7/9/2007 Expressive Phonological Impairment and the Development of Literacy Margot E. Kelman, Ph.D., CCC-SLP, Early Language and Literacy Consultant, Wichita, KS | |
| 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. Terminology 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. Severity 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. Assessment of Severity The manner in which severity is assessed is variable. For example, some studies use conventional articulation tests with well-known noncomplex single-word production to judge speech sound ability. Upon completion of the test, the total number of errors is calculated. A child who has multiple sound omissions may earn a comparable score to a child with a sound distortion on one or two commonly occurring phonemes. A child who has a “lisp” may fall in the moderate-to-severe category due to the frequency of the /s/ and /z/ phonemes on the test, thus inflating his or her speech deficit. In this case, intelligibility is not taken into account. In contrast, other studies employ an in-depth assessment of phonological patterns, providing considerably more detail regarding error patterns. The use of different types of assessment instruments results in inconsistencies in reporting severity levels of participants. These factors play a role in the variable outcome of studies designed to determine if a relationship exists between EPI and literacy. The discrepancies in published studies have made the relationship between EPI and the development of literacy somewhat ambiguous. There are differing views among researchers regarding factors that may predispose children with EPI to reading difficulties. These views are explained in the following section. EPI and Reading Achievement Some studies have shown a limited relationship between reading achievement and expressive phonology (e.g., Bishop & Adams, 1990; Catts, 1993). These studies suggest that EPI alone is not closely associated with problems in early reading achievement. Rather, when EPI is accompanied by language impairments, children experience literacy deficits. Bishop and Adams (1990) examined language and literacy outcomes in 83 third-grade children (8-year-olds) who were previously identified as having delayed speech or language skills at 4 years of age. The severity level of the children was not identified in the study. A weak relationship between EPI and literacy was found, prompting the assertion that children with widespread delays in language were more likely to demonstrate reading and spelling problems in the future. The “critical age hypothesis” evolved from this research, stating that if a child’s speech difficulty has resolved by 5½ years of age, they were less likely to encounter reading and spelling difficulties later. A weak relationship between EPI and reading achievement was also found by Catts (1993). The reading achievement of three groups of second-grade children was examined: those with language impairment, those with phonological impairment, and a control group of peers who were typical. From this study, Catts concluded that articulation ability was not related to reading achievement. Many in the articulation group performed at or above expected levels in reading achievement. Children in this study were evaluated with a single-word articulation test and many children scored below average but within their age range of articulation ability. The participants were not phonologically impaired; therefore, the results of this study must be interpreted with caution. In several other studies, a correlation between EPI and reading ability was established. Webster and Plante (1992) compared the phonological awareness ability of 11 children (ages 6-8 years) with EPI to 11 children with typical phonology. The children identified as EPI were given a severity rating of moderate-to-severe. It was found that the children with EPI did more poorly than their peers who were typical on each segmentation and word recognition task. Webster and Plante found the children with EPI exhibited substantially more variability than their peers who were typical across each task, increasing the risk of reading difficulties. Bird, Bishop, & Freeman (1995) conducted a longitudinal study of 31 boys (ages 5–7 years) to examine the relationship of EPI, phonological awareness, and reading ability. Children were identified as having moderate-to-severe phonological impairments. Bird and colleagues found the children with EPI scored well below those with age-appropriate phonological skills. Larrivee and Catts (1999) further examined the relationship between EPI and early reading achievement. A significant correlation was found between expressive phonological ability and early reading achievement in children identified with moderate-to-severe EPI, revealing EPI as an early sign of potential reading disabilities. A notable finding of this study was that reading achievement was more highly correlated to EPI when the expressive phonology was measured in multisyllabic words and a nonword repetition task rather than a single-word articulation test. In other words, the strength of the relationship depended on the way in which expressive phonology was measured. Therefore, Larrivee and Catts concluded that the assessment instrument plays an important role in determining appropriate severity, thus affecting outcomes. Rvachew, Ohberg, Grawburg, and Heyding (2003) conducted a study similar to that of Webster and Plante (1992), comparing the relationship between EPI and phonological awareness ability. Participants were 26 children, 4 years of age, with moderate-to-severe delays in expressive phonology. Receptive language was within normal limits. Findings concurred with Webster and Plante, Bird and colleagues (1995), and Larrivee and Catts (1999) that children with EPI are at greater risk of literacy problems than their peers who were typical. Dodd, Russell, and Oerlemans (1993) studied past histories of children identified as phonologically impaired and compared them to past histories of children identified as articulation impaired and to a control group of peers who were typical. The children identified as phonologically impaired scored lower on all tasks of reading ability than the children who had articulation problems and their peers, concluding that a past history of moderate-to-severe phonological deficits places children at higher risk of later reading and spelling difficulties. Nathan, Stackhouse, Goulandris, and Snowling (2004) studied 47 children with speech difficulties between the ages of 4–7 years. The children in this study identified as moderate-to-severe EPI were found to be at risk for later reading difficulties. Research by Carroll and Snowling (2004) compared the reading difficulties of children with EPI and those with dyslexia. The results of their study confirmed the view that children with EPI (in the absence of language impairments) are on a continuum of risk of reading difficulties with children who have a family history of dyslexia. The shared risk factor appeared as a problem of phonological processing, traced to poorly specified phonological representations. Phonological Representations and Reading Achievement Phonological representation, the underlying skill of recall and storage of speech sound aspects of a word, is influential in developing phonological abilities. This underlying representation is necessary to make the connection between phonology, phonological awareness, and ultimately reading and spelling. Reading difficulties can be traced to poorly specified underlying phonological representations (Fowler, 1991; Metsala, 1997; Swan & Goswami, 1997). According to Mody (2003), individuals who read poorly store words as a complex of loosely organized gestures (incomplete representations). Readers who struggle lack a full understanding of the phonetic properties of a sound, often grappling with phoneme identification and discrimination. In contrast, readers who are fluent draw on phonological awareness skills to access fully specified representations that are well-coded in articulatory detail, enabling them to easily sound out words. It is theorized that children with EPI may experience difficulties in the storage and retrieval of phonological representations, making them vulnerable to reading problems. A study by Sutherland and Gillon (2005) examined underlying phonological representations in preschool children with speech impairment. Children identified with speech impairment performed significantly below the children without speech impairment on receptive-based tasks that did not rely on the children’s motor speech system. Phonological Awareness and Reading Achievement Children with EPI are at risk for literacy problems if they have deficits in phonological awareness skills (Larrivee & Catts, 1999; Stackhouse & Wells, 1997; Webster & Plante, 1992). Phonological awareness, the awareness of the sound structure of spoken language (Stackhouse & Wells, 1997), is highly correlated with reading ability (Bradley & Bryant, 1983, 1985; Liberman & Shankweiler, 1985; Stanovich, 2000; Wagner & Torgesen, 1987). In the early stages of reading, the child’s ability to phonologically decode the printed word is related to word recognition proficiency. Children who are struggling with phonological decoding or phonological awareness skills frequently have difficulty in the alphabetic phase of reading development (Frith, 1985). In some children with EPI, deficits in phonological awareness have resulted in difficulties with reading and spelling ability even after intelligibility issues have been resolved (Bird et al., 1995; Clarke-Klein & Hodson, 1995). A phonological awareness intervention study by Gillon (2000) included children with EPI who received phonological awareness intervention, children with EPI who received traditional intervention without phonological awareness, and a control group of peers who were typical. Results from this study revealed that children with EPI who received phonological awareness intervention made greater gains in phonological awareness, speech production, reading ability, and reading comprehension than the group who received the traditional intervention. In addition, the children with EPI who received phonological awareness intervention also made gains in speech production without direct intervention for phonological patterns. Furthermore, in a post-intervention study (Gillon, 2002), children with EPI who received the phonological awareness intervention sustained their growth in phonological awareness. The children with EPI and traditional intervention did not show any growth in phonological awareness skills. Implications for Speech-Language Pathologists Although it is primarily the classroom teacher’s ultimate responsibility to teach children to read and write, speech-language pathologists are playing a more active role than ever before in the prevention, identification, and remediation of reading difficulties. Since publication of the American Speech-Language-Hearing Association’s position statement “Roles and Responsibilities of Speech-Language Pathologists with Respect to Reading and Writing in Children and Adults” (ASHA, 2001), it is now common practice for speech-language pathologists to assess the phonological awareness and literacy skills of children with language impairment or speech and language difficulties. Children with EPI (without language impairment) are not always routinely evaluated for reading ability even though children identified with EPI are at considerable risk for difficulties with literacy development. In addition, children with EPI are at risk for impairments in the storage and retrieval of phonological representations. Early identification is essential to decrease a child’s risk of reading difficulties. Speech-language pathologists can assist classroom teachers become aware of the role phonology plays in literacy development. It is advisable that any child who is identified with a phonologically based speech problem be routinely screened for underlying phonological representations, phonological awareness, and literacy skills. The speech-language pathologist is uniquely qualified to initiate the screening process once the child has been identified with EPI. Any child who does not pass the screening will require a more comprehensive assessment of phonological representations, phonological awareness, and literacy skills. A referral to the classroom teacher, special educator, or reading specialist may be necessary, depending on the roles and responsibilities of each professional in the school setting. In addition, periodic assessments of literacy abilities, even after intelligibility gains are made, also need to be conducted. Phonological awareness activities and literacy skills may be included in an intervention program or integrated in the classroom setting. The synthesis of phonological awareness and letter knowledge activities with speech intelligibility practice may facilitate the development of more precise underlying representations. The speech-language pathologist must work collaboratively with other educators to determine the optimal methods to meet the learning needs of children with EPI. Professionals including academicians, speech-language pathologists, classroom teachers, special educators, and reading specialists must work together to help children with EPI develop proficiencies in critical reading, writing, and spelling skills. By addressing these areas early, future problems and difficulties can be prevented. Future Research Future evidence-based research is necessary to determine the specific effects of EPI on the development of reading and spelling skills. Further investigation of underlying phonological representations of children with speech impairment is needed. 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