A Comparison of Phonological Processing Skills of ...

A Comparison of Phonological Processing Skills of Children With Mild to Moderate Sensorineural Hearing Loss and Children With Dyslexia Jungjun Park, Linda J. Lombardino

American Annals of the Deaf, Volume 157, Number 3, Summer 2012, pp. 289-306 (Article) Published by Gallaudet University Press DOI: 10.1353/aad.2012.1621

For additional information about this article http://muse.jhu.edu/journals/aad/summary/v157/157.3.park.html

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Park, J., & Lombardino, L. J. (2012). A comparison of phonological processing skills of children with mild to moderate sensorineural hearing loss and children with dyslexia. American Annals of the Deaf, 157(3), 289–306.

A COMPARISON OF PHONOLOGICAL PROCESSING SKILLS OF CHILDREN WITH MILD TO MODERATE SENSORINEURAL HEARING LOSS AND CHILDREN WITH DYSLEXIA

U

JUNGJUN PARK AND LINDA J. LOMBARDINO

PARK IS AN ASSISTANT PROFESSOR, DEPARTMENT OF COMMUNICATION SCIENCES AND DISORDERS, BAYLOR UNIVERSITY, WACO, TX. LOMBARDINO IS A PROFESSOR, SCHOOL OF SPECIAL EDUCATION, SCHOOL PSYCHOLOGY, AND EARLY CHILDHOOD STUDIES, UNIVERSITY OF FLORIDA, GAINESVILLE.

C O M P R E H E N S I V E Test of Phonological Processes (Wagner, Torgesen, & Rashotte, 1999), the researchers compared strengths and weaknesses in phonological processing skills in three groups: 21 children with mild to moderate sensorineural hearing loss (MSNH group), 29 children with dyslexia, and 30 age-matched controls. The MSNH group showed phonological deficits that were restricted to phonological awareness tasks (elision/blending) and a phonological memory task (nonword repetition), yet exhibited unimpaired rapid naming ability. Children with dyslexia showed deficits in all 3 phonological constructs. Finally, both degree of hearing loss and age at which hearing loss was identified in the MSNH group were related to the children’s phonological processing skills. Because of their deteriorated phonological skills, children with MSNH may be at risk of starting school with weaknesses in early literacy skills. Implications for practice aimed at improving phonological and literacy skills of these children are described.

SING THE

Keywords: phonological processing, phonological awareness, phonological memory, phonological representation, phonological code, auditory deprivation, mild to moderate sensorineural hearing loss, dyslexia, rapid naming

A resurgence of interest in the development of reading over the past three decades has established unequivocally that atypical phonological processing ability is a hallmark of poor readers (Adams, 1990; Blachman, 1997; Bradley & Bryant, 1985; Brady, 1991, 1997; Fletcher et al., 1994; Fowler, 1991; Kamhi & Koenig, 1985; Katz, 1986; I. Y. Liberman, 1971, 1973; I. Y. Liberman,

Shankweiler, & A. M. Liberman, 1989; Lyon, S. A. Shaywitz, & B. A. Shaywitz, 2003; Mody, 2003; Share & Stanovich, 1995; Snowling, 2001; Stanovich, 1990; Torgesen, Rashotte, & Wagner, 1994; Vellutino, Fletcher, Snowling, & Scanlon, 2004; Vellutino & Scanlon, 1987). The impact of sensorineural hearing loss on children’s development of skilled reading has been investigated in the literature for many decades (Blair, Peterson, & Viehweg, 1985; Briscoe, Bishop, & Norbury, 2002; Delage &Tuller, 2007; Gibbs, 2004; Halliday & Bishop, 2005; Hansson, Forsberg, Löfqvist, Mäki-Torkko, & Sahlén, 2004; Kodman Jr., 1963; Stelma-

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN chowicz, Pittman, Hoover, & Lewis, 2004). Though relationships between hearing loss and phonology have been investigated in children with conductive hearing loss (Friel-Patti & Finitzo, 1990; Mody, Studdert-Kennedy, & Brady, 1997) or with severe to profound hearing loss (Boynton, 1995; Hanson, Goodell, & Perfetti, 1991), only a handful of studies exist to identify the strengths and weaknesses related to the phonological skill development of children with mild to moderate sensorineural hearing loss (MSNH) (Briscoe al., 2001; J. Davis, Elffenbein, Schum, & Bentler, 1986; Delage & Tuller, 2007; Gibbs, 2004; Gilbertson & Kamhi, 1995; Halliday & Bishop, 2005; Plapinger, & Sikora, 1995). Prelingual MSNH is typically defined as a 25–70 dB hearing loss (HL) in the better ear. A loss of this nature has the potential to degrade the incoming acoustic signal and result in inaccurate, underspecified, indistinct, or low-quality phonological representations in the lexical system (Elbro, 1998; Nittrouer & Burton, 2005). Because there is a well-established relationship between phonological processing and reading abilities in children in the early elementary grades with or without reading disorders (Hogan, Catts, & Little, 2005; Wilson & Lesaux, 2001), it is reasonable to expect that children with MSNH, having impoverished phonological representation and decreased phonological processing skills, will exhibit deficient reading skills when compared to their typically developing hearing peers. Nittrouer and Burton (2005) posit that peripheral hearing loss should provide a unique opportunity to examine the validity of the phonological core deficit hypothesis, the basic tenet of which is that weaknesses in one or more phonological processing skills lie at the root of

many developmental reading disorders (Beitchman & Young, 1997; Fowler, 1991; Hansen & Bowey, 1994; Metsala, 1997; Mody, 2003; S. Shaywitz, 1998; Snowling, Nation, Moxham, Gallagher, & Frith, 1997; Swan & Goswami, 1997; Vellutino, 1979). A greater understanding of relationships between sensorineural hearing loss and phonological processing skills in young children with even mild to moderate degrees of hearing loss should help to elucidate the degree to which phonological processing skills (e.g., phonological awareness, phonological retrieval) can be dissociated, and to inform clinicians and teachers about the need to provide explicit phonological instruction to children with hearing impairments during the stages of emergent literacy development around 4–5 years of age. This is approximately the age range in which the majority of children who have MSNH are identified. This is also the period beyond which an enormously important growth in language and literacy development occurs in typically developing children (Delage & Tuller, 2007). Core Phonological Deficit Theory as It Applies to Children With MSNH Around three decades ago, articles unanimously reported the significant academic underachievement of children with mild (Blair et al., 1985) and mild to severe ( J. Davis, 1977) hearing loss. Since then, investigators have attempted to document the strengths and weaknesses of phonological skill in children with MSNH on the premise that an intact phonological system provides the foundation for both spoken language and reading skills (Briscoe, et al., 2001; Gibbs, 2004; Most, Aram, & Andorn, 2006; Stelmachowicz et al., 2004). Studies of reading deficits based on

the phonological core deficit hypothesis represent a convergence of several lines of research, all of which have shown that students with developmental reading deficits have deficits in one or more of three associated components of phonological processing (Wagner & Torgesen, 1987): (a) phonological awareness (I. Y. Liberman & A. M. Liberman, 1990; I. Y. Liberman & Shankweiler, 1985; Stanovich, 1988, Wagner & Torgesen, 1987); (b) phonological memory (Berninger, 2008; Pennington, 2009; Swanson, Zheng, & Jerman, 2009); and (c) speed of access to phonological codes (Stoodley & Stein, 2006; Wolf & Bowers, 1999; Wolf, Bowers, & Biddle, 2000). It is now well established that young children with dyslexia perform poorly on phonological tasks that require access to and manipulation of the speech segments of words. One explanation for this welldocumented difficulty is that phonological representations in the mental lexical system of the child with dyslexia are indistinct or are not fully segmentally organized into sequences of distinct phonemes (Bradley & Bryant, 1978; Elbro, 1996, 1998; Elbro & Jensen, 2005). Investigations of phonological processing and reading abilities in children with mild to moderate hearing impairment have found that the children’s reading scores were comparable to those of normally hearing children in spite of demonstrations of depressed phonological processing efficiency (Bishop & Norbury, 2002; Briscoe et al., 2001; Gibbs, 2004; Nittrouer, 1996; Nittrouer & Burton, 2005). These data suggest that precise phonological representations may not be as critical for learning to read as previously suggested in the phonological processing literature on children with normal hearing who are struggling readers (Byrne, 2002; Snowling, 2000).

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In an attempt to examine phonological processing profiles across clinical populations, Briscoe et al. (2001) compared the phonological processing, language, and literacy skills of children with MSNH (range of pure tone average in the better ear: 20–70 dB HL) to those of children with specific language impairment who ranged from 5 to 10 years of age. All subjects were tested with a battery of phonological processing tasks that consisted of phonemic discrimination, an onsetrime detection task to measure phonological awareness, a nonword repetition task to measure short-term retrieval of novel sound sequences, and digit recall tasks to measure shortterm retrieval of digit sequences. Interesting patterns emerged within and across groups. Both clinical groups showed depressed phonological processing skills on a number of tasks, including phonological discrimination, phonological awareness, and nonword repetition. In fact, 9 of 19 subjects with hearing loss had standard scores below the 10th percentile on at least two tests of the phonological skills, with phonological discrimination and nonword repetition emerging as the most challenging tasks for this group. Lower performance levels on tasks of phonological processing were associated with poorer language skills and higher hearing thresholds. As expected, the group with specific language impairment exhibited marked deficits in spoken language, word reading, decoding, and reading comprehension; however the MSNH group performed much more like their control peers in these same areas. This unexpected observation of no clear link between phonological processing skills and language and literacy skills led Briscoe et al. to suggest that perhaps the nature of phonological processing profiles of children with MSNH is different

from that documented in children with normal hearing who have reading deficits (e.g., children with dyslexia) or that phonological impairment is not a sufficient condition for later reading problems and other concomitant cognitive impairments that may be strongly related to developmental reading disabilities. Gibbs (2004) compared 15 children with MSNH between 7 and 9 years of age to normally hearing controls on two relatively easy tasks of phonological awareness, rhyme detection and phoneme detection, and on one test of phonological memory. Subjects with hearing loss lagged behind the age-matched hearing controls on all tasks. Specifically, they performed at the level of 6-year-old subjects with normal hearing, a finding that suggests that their phonological awareness skills were delayed 1–3 years. However, hearing impaired subjects’ reading skills were comparable to those of their age-matched peers, and their performance on phonological awareness measures was significantly correlated with degree of hearing loss but not correlated with their reading scores. Gibbs concluded that “at least some reading may be possible” (p. 24) even without the support of phonological processing skills. It is evident that the findings of both Briscoe et al. (2001) and Gibbs pose a challenge to phonological core deficit theory. In a preliminary study, Stelmachowicz et al. (2004) investigated the importance of high-frequency audibility in the speech and language development of children with moderate sensorineural hearing loss. Phonological skills were compared in three groups of children: (a) normally hearing children, (b) children with hearing impairments who were identified and aided prior to age 12 months (early identified), and (c) children with hear-

ing impairments who were identified after age 12 months of age but before age 4 years (late identified). The children in the early identified group were delayed for all English phonemes in spite of early rehabilitation; the children in the late identified group similarly showed substantial delays in phoneme acquisition. As expected, delays for children in the late identified group were much longer. These findings are consistent with research showing that the speech perception skills of children with MSNH are significantly poorer than those of their normally hearing peers on various speech perception listening tasks with varied signal-to-noise ratios (Bess, 1999; Crandell & Smaldino, 1995; Finitzo-Heiber & Tillman, 1978; Litovsky, Johnstone, & Godar, 2006; Smaldino & Crandell, 1999) and underscore the vulnerability of the auditory system when it is deprived of or delayed in receiving precise acoustic information for speech perception. Previous studies of phonological processing in children with mild to moderate hearing loss have provided a much wider lens for viewing relationships between these phonological skills and children’s reading achievement. The purpose of the present study was to expand this line of research by examining a broader array of phonological awareness skills that included retrieval of phonological information from long-term memory using tasks of rapid naming and by comparing children with mild to moderate hearing loss to children with dyslexia. Children with a diagnosis of dyslexia were chosen as a clinical comparison group because, like children with hearing loss, they exhibit weaknesses in the areas of phonological processing, reading, and spelling in spite of adequate conceptual and problem-solving abilities. However, different causal factors are attributed

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN to the academic difficulties these two groups experience. While hearing loss results from a sensory deficit, dyslexia results from a deficit in the neural network of the brain that subserves written language. Due to these similarities and differences, we expected to find that both groups would show difficulties on tasks of phonological processing, but that the profiles of their deficits would differ. In the study, we sought to address two questions: • What are the strengths and weaknesses of the phonological processing skills of children with MSNH in comparison to those of children with dyslexia? That is, how are the patterns of phonological processing skills of children with MSNH and dyslexia distinct from each other? • How are audiologic background measures (i.e., better-ear PTA, age at first use of amplification, and duration of hearing aid use) associated with phonological skills of children with MSNH? How much unique variance in each component of phonological processing is explained by these variables in children with MSNH? Method

Participants The present study included 80 English-speaking monolingual children between 7 and 12 years of age. Twenty-one children had a congenital, binaural mild to moderate sensori neural hearing loss (MSNH group), 30 had been previously diagnosed with dyslexia (DYS group), and 29 were age-matched typically developing controls with normal hearing (CA group). Normal hearing was defined as thresholds at or better than 20 dB HL at octave frequencies from 0.25 to

8.00 kHz. In an effort to replicate the study by Briscoe et al. (2001), children with mild hearing loss and children with moderate hearing loss were chosen on the basis of their PTA thresholds in the better ear for 0.5, 1.0, 2.0, and 4.0 kHz (British Society of Audiology, 1988). Ten children had mild hearing loss, defined as a PTA threshold of 20–40 dB HL, and 11 children had moderate hearing loss, defined as a PTA threshold of 41–70 dB HL. All participants had a standard score of 80 or better on the Test of Nonverbal Intelligence-3 (TONI-3; Brown, Sherbenou, & Johnsen, 1997).

MSNH Group Participants in the MSNH group met the following selection criteria: (a) presented with a prelingual, symmetrical, and bilateral sensorineural hearing loss (normal tympanometry and air-bone gaps no greater than 10 dB at three or more frequencies); (b) showed no signs of central nervous system deficits; (c) attended a mainstream school that used speech as the primary communication mode; (d) showed no sign of middle ear infection at the time of testing; and (e) reportedly used binaural hearing aids regularly. Initially, 33 children with hearing loss were contacted across 14 public elementary schools located in five school districts in the southeastern United States. Twelve of the children did not satisfy the inclusion criteria and were excluded from the study. Twenty-one children, 11 boys and 10 girls between the ages of 7 years 1 month and 12 years 8 months (M = 9 years 2 months, SD = 1 year 6 months), were included in the MSNH group. The mean PTA for the MSNH group using their better ear was 46.7 dB HL (SD = 14.1). The mean speech recognition threshold values were 41.90

(SD = 15.30 dB) and 46.57 (SD = 21.6 dB) dB HL for the left and right ears, respectively. Mean word-recognition scores were 86.8% (SD = 21.1%) and 87.4% (SD = 23.9%) for the left and right ears, respectively. The groups’ mean age of initial hearing loss diagnosis was 2 years 11 months (SD = 18 months, range = 7–72 months), the mean age at which they were fitted with hearing aids was 3 years 9 months, and their mean length of hearing aid use was 5 years 7 months (SD = 26 months, range: 11–74 months). All but one child was fitted with binaural hearing aids at the time of the initial audiologic testing. The exception was a subject whose hearing loss was very mild (left ear PTA = 25 dB HL, right ear PTA = 27 dB HL) and whose word recognition scores for each ear was 100% at the time of testing. Based on data from a parent questionnaire, 14 children (67%) in the MSNH group had received speech and language therapy services, 6 (29%) were still receiving therapy, and only 1 (4%) had not received any services. Figure 1 presents the average threshold data for the MSNH group. Audiologic data on participants in the MSNH group are shown in Table 1.

DYS Group The data of children with dyslexia were obtained from a large archival database of children with reading disabilities who were tested and diagnosed with dyslexia at a university reading diagnostics clinic. The DYS group was included as a clinical contrast group to determine whether the pattern of phonological deficits under study differed across the groups. Subjects were chosen if they had a clear diagnosis of dyslexia and if they had been given the same phonological processing and reading battery that was used to test participants in the

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Figure 1

Box-and-Whisker Plots of Pure Tone Thresholds for the MSNH Group

Institute, 1996] at octave frequencies from 250 through 8000 Hz). The assessment instruments used to diagnose the subjects include these five standardized tests:

Notes. MSNH, mild to moderate sensorineural hearing loss. The central longitudinal line represents the median value. The interquartile range of values obtained is represented by the box, with the median represented by the solid horizontal line. The range of thresholds for each frequency is shown by the whiskers.

MSNH group. Data on 30 children, 17 boys and 13 girls, between the ages of 7 years 2 months and 12 years 8 months (M = 9 years 8 months, SD = 1 year 8 months), were used to create the DYS group. The subjects in the DYS database were tested independently by the second author using several standardized tests of phonological processing, language, and reading. Participants were given a diagnosis of dyslexia if they 1. Presented with a history of difficulty in learning early literacy skills, such as being able to name letters, along with difficulty with word-level reading as reported by parents and/or teachers. 2. Showed deficits on at least two norm-referenced measures of a

3.

4.

5.

6.

battery of word-level reading skills that included timed and untimed word recognition and nonword decoding. Demonstrated weakness in at least one of the three components of phonological processing skills. Obtained scaled scores within the normal range on standardized tests of spoken-language syntax and expressive vocabulary. Demonstrated a strength in reading and/or listening comprehension in contrast to word-level reading and reading fluency. Demonstrated normal hearing acuity within normal limits bilaterally (i.e., pure tone airconduction thresholds less than or equal to 20 dB HL [American National Standards

1. The Woodcock Reading Mastery Test—Revised (WRMT-R; Woodcock, 1987) was used to measure (a) untimed word recognition (M = 84.93, SD = 13.41); (b) nonword decoding (M = 82.63, SD = 12.03), and (c) reading comprehension (M = 84.41, SD = 14.33). 2. The Test of Word Reading Efficiency (TOWRE; Torgesen, Wagner, & Rashotte, 1999) was used to measure (a) timed word recognition (M for sight word efficiency = 81.48, SD = 11.99), and (b) nonword decoding (M for phonemic decoding efficiency = 83.33, SD = 13.87). 3. The Gray Oral Reading Test—3 (GORT-3; Weiderholt & Bryant, 1992) was used to measures text-level reading fluency (group passage fluency mean = 6.07, SD = 2.77). 4. The Syntax Construction subtest of the Comprehensive Assessment of Spoken Language (Carrrow-Woolfolk, 1999, M = 97.33, SD = 13.22) and the Expressive Vocabulary Test (EVT; Williams, 1997, M = 101.86, SD = 15.32) were used to measure syntactic knowledge and expressive vocabulary, respectively. 5. Seven subtests from the Comprehensive Test of Phonological Processes (CTOPP; Wagner, Torgesen, & Rashotte, 1999) were used to measure phonological processing skills. (See Table 3 for the scores.)

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN Table 1

Characteristics of the MSNH Group

Gender

Age in months

PTAa

SRT b

1 2 3 4 5 6 7 8 9 10 11 12 13 14

F M F M F F M F F M M M M M

115 111 114 100 112 106 86 125 115 121 91 122 99 122

63 58 38 69 68 38 31 27 60 65 38 48 41 41

55 55 40 65 63 35 30 25 55 55 40 48 35 40

15 16 17 18 19 20 21 M SD

M M F F M M M

84 152 84 152 106 111 116 111.6 18.4

43 41 41 43 28 45 58 46.9 12.9

40 40 35 35 25 45 55 43.6 11.7

Subject

Age Age (months) (months) at initial at initial identification amplification of hearing loss fitting

Duration (months) of hearing aid use

Etiology

Hearing aid type

24 48 30 20 27 42 44 36 37 32 27 35 48 49

24 50 33 20 28 42 47 37 37 33 29 37 50 49

91 61 81 80 84 64 39 88 78 89 64 87 49 73

Genetic Unknown Genetic Unknown Genetic Genetic Unknown Unknown Genetic Genetic Unknown Genetic Unknown Genetic

Phonak Pico Forte Oticon 380P Oticon 39 PL Oticon 380P Oticon Multi-Focus Phonak Sono Forte Unitron UM 60 Oticon 39 PL Unitron Icon Telex 366 Phonak Pico Forte Telex 366 Oticon 380P Oticon 380P

29 46 41 72 * 24 24 36.85 13.50

31 48 42 75 * 27 25 37.9 12.9

55 104 42 77 * 84 91 76.8 18.1

Unknown Unknown Genetic Unknown Unknown Unknown Unknown

Phonak Sono Forte Unitron Icon Phonak Pico Forte Unitron Icon Unitron UM 60 Oticon 38 P Rion HB 75AL

Notes. MSNH, mild to moderate sensorineural hearing loss. aPure tone average for the better ear in dB hearing loss (average of 0.5, 1.0, 2.0, and 4.0 kHz). bSpeech recognition thresholds for the better ear in dB hearing loss. *No information was available.

Control Group Typically developing children who had normal hearing skills and who matched for chronological age with the MSNH and DYS groups were recruited from the local school districts. Twenty-nine children, 15 boys and 14 girls, between the ages of 7 years 5 months and 11 years 2 months (M = 9 years 3 months, SD = 1 year 1 month) were selected for the control (CA) group. Based on data from a parent questionnaire, none of the subjects in the CA group were known to have a history of speech, language, or hearing problems, or any type of excep-

tional educational needs. All subjects in the CA group had pure tone thresholds of 20 dB HL or better at all frequencies from 250 to 8000 Hz, and word recognition scores ranging from 94% to 100% for the Central Institute for the Deaf (CID) W-22 word lists (M = 97.00, SD = 2.95). Table 2 shows demographic data for the MSNH, CA, and DYS groups. As we have already noted, previous studies had documented that the children with MSNH were much closer to the normal range than expected given their phonological processing deficits (Briscoe et al., 2001; Gibbs,

2004; Moeller, Tomblin, YoshinagaItano, Connor, & Jerger, 2007). Given previously obtained reading research data on reading abilities in MSNH and DYS populations, we expected that our MSNH group’s reading skills would be superior to those of the DYS group but inferior to those of our CA group. As a part of preliminary analyses of word-level reading skills of the three groups, participants in the MSNH and CA groups were administered the same tests of word-level reading skills from the WRMT-R that were included in the diagnostic battery for the DYS group: the Word

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Table 2

Demographic Data and Standard Scores on Control Variables for the Three Subject Groups CA group (n = 29, 44% female)

Age (months) Grade (years, months) PTAa EVT score TONI-3 score

MSNH group (n=21, 38% female)

DYS group (n=30, 40% female)

M

SD

M

SD

M

SD

111.9 3.7 3.31 103.4 112.52

13.9 1.1 3.91 10.45 15.84

110.8 3.4 46.05 89.95 99.38

18.7 1.6 12.66 13.21 13.16

116.6 3.9 n/a 101.86 102.33

20.3 1.6 n/a 15.32 12.75

Notes. MSNH group: subjects with mild to moderate sensorineural hearing loss. CA group: controls matched for chronological age. DYS group: subjects with dyslexia. EVT, Expressive Vocabulary Test. TONI-3, Test of Nonverbal Intelligence (3rd ed.). aPure tone average on 0.5, 1, 2, and 4 kHz.

Identification and Word Attack subtests. As expected, the MSNH group scored significantly worse than the CA group on the Word Identification (i.e., real word reading) task, MCA = 109.34, MMSNH = 93.71, t(48) = 6.219, p < .001, but significantly better than the DYS group, MDYS = 82.63, t(49) = 3.496, p = .001. Similarly, the MSNH group performed significantly worse than the CA group on the Word Attack (i.e., nonword decoding) test, MCA = 107.0, MMSNH = 92.81, t(48) = 5.871, p < .001, but significantly better than the DYS group, MDYS = 84.63, t(49) = 3.074, p = .003.

Procedure Both the CA group and the MSNH group were administered a comprehensive battery of tests of phonological processing, reading, and oral language skills. The same set of tests was administered that had been used with the DYS group, whose data were obtained from an archived database. The entire assessment took approximately 3 hours (two separate sessions). The children in the CA and MSNH groups also received a diagnostic hearing evaluation in the first session. In the first session, general information about the tests and the testing procedure was explained to the students and their parents, and a questionnaire was administered to

the parents. After completion of a detailed case history, each participant completed all audiologic tests within 1 hour. In the second session, all phonological processing, reading, and spoken-language tests were administered within 90 minutes. Parent/ guardian consent and child assent, as required for human participant protection, were granted for all participating students. All subjects were tested individually by two examiners (the first author and a graduate research assistant under supervision of a licensed speech-language pathologist). To ensure reliable test administration and scoring, additional instruction was provided whenever any deviation from the test manual occurred until the testers were able to demonstrate complete compliance with the testing protocols.

Audiologic Measures All audiologic tests administered to the CA and MSNH groups were conducted by a certified audiologist and a doctoral student in a clinical doctor of audiology program under the supervision of a certified audiologist. The hearing acuity of the children was assessed in a conventional manner since all participants were age 7 years or older. All audiologic measurements were administered by means of ER-3A insert earphones, and all equipment was calibrated in accordance with

ANSI S3.6–1996. Both the left and right ears were tested to determine the better ear. The audiologic test battery consisted of (a) air-conduction pure tone threshold testing at 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz done with a GSI 61 clinical audiometer; (b) a speech recognition threshold testing; (c) word recognition testing at 40 dB sensation level or at the most comfortable loudness level; and (d) tympanometry for each ear. Speech reception thresholds were measured via live voice by means of CID W-1 spondaic word lists, and word recognition percentile score were obtained with recorded W-22 word lists (Auditec Revised Auditory Tests CD). All participants were required to pass a tympanometry screening to ensure normal eardrum and middle ear functions. Only one normally hearing participant had a middle ear infection at the time of testing. Three weeks later, this subject was retested after the infection had been treated. Normal hearing abilities were confirmed for all children with dyslexia through hearing screenings on the day of testing by a certified audiologist.

Phonological Processing Measures Participants’ phonological processing skills were measured with the same set of seven subtests from the CTOPP

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN as had been used with the subjects with dyslexia. The CTOPP is an individually administered, norm-referenced measure that is used to evaluate a wide range of aspects of an individual’s phonological processing. A threepart model, based on earlier studies in this area, has been presented by the test developers (Torgesen & Wagner, 1998; Wagner & Torgesen, 1987) to produce three composite scores. Each composite score was derived by adding the standard scores of two subtests and converting the sum to a composite score: Elision and Blending Words for the phonological awareness composite scores (PA), Memory for Digits and Nonword Repetition for the phonological memory composite scores (PM), and Rapid Letter Naming and Rapid Digit Naming for the rapid naming composite scores (RAN). We also included the Rapid Object Naming subtest as an additional measure of rapid naming skill. Each composite score has a mean of 100 and a standard deviation of 15 points. Reliability estimates of internal consistency of the CTOPP composite scores exceed the Cronbach’s alpha of .80 (Wagner et al., 1999). A short description of the seven tests of the CTOPP used in the present study follows. The Elision subtest requires participants to listen to a spoken word; delete a phoneme in either the initial, final, or medial position from the word; then produce a new word (e.g., “Say tiger without saying /g/” [tire]). Scoring is based on the number of accurate responses.The Blending Words test requires participants to listen to isolated syllables and phonemes in a spoken word, blend the sounds (e.g., “What word do these sounds make?: /hæm/ /er/?” [hammer]), and produce the word. Scoring is based on the number of accurate responses. In the three rapid naming tests, participants are shown a

visual display of randomly presented items and asked to name them in sequence as fast as they can. The Rapid Digit Naming test consists of a set of six digits (4, 7, 8, 5, 2, 3) that are displayed in random sequence six times for a total of 36 stimuli. Participants are asked to say the names of the digits from left to right as quickly as possible, and the total time to complete the task is recorded. Similarly, in the Rapid Letter Naming test, participants are asked to say, as fast as possible, the names of six letters (a, n, s, t, k, c) that have been arranged randomly in four rows of nine letters each. The Rapid Object Naming test uses line drawings of six common objects (chair, fish, key, star, pencil, and boat). The pictures are presented in four rows of nine pictures, again totaling 72 items on two pages. The time in seconds that it takes to name the 72 items in the display is recorded. Standardized scores are provided for individuals 5–24 years old on a 0–20 scale, with an average score of 10. For the Nonword Repetition and Memory for Digit tests, subjects are required to listen to pre-recorded auditory stimuli and repeat back the stimuli verbatim. Using live voice, we allowed the children with hearing loss to practice these tasks on nontest items to ensure that they could accurately process the stimuli, and without the benefit of speechreading. All subjects in the MSNH group passed this modified pretest with 100% accuracy. The Nonword Repetition subtest consists of 18 nonwords of increasing difficulty (e.g., “chaseedoolid”), presented on a CD and repeated by the participant. Nonword repetition is considered to be a pure measure of phonological short-term memory because novel phonological representations must be maintained in memory long enough for one to reproduce

them. On the Memory for Digits task, participants are required to listen to strings of numbers (ranging from two to seven digits) spoken by the examiner and then repeat them verbatim. Scoring is based on the number of accurate responses. The MSNH group’s responses on all of phonological processing and expressive language tests were digitally recorded (Olympus Model DS-40). The recorded audio data were transcribed by two graduate students, and analyzed later for reliable scoring. For all tests, participants with hearing loss were wearing hearing aids in both ears. All oral instructions were given as specified in test manuals. Throughout data collection, none of the subjects showed difficulty understanding the tasks.

Vocabulary Skills of the MSNH Group It is now well established that vocabulary size and phonological processing skills are significantly associated. For instance, Metsala and Walley’s (1998) lexical restructuring model posits that as children’s spoken vocabulary grows, their phonological representations need to become increasingly segmented, expanded, distinct, and specific to allow for efficient lexical retrieval and efficient storage (Foy & Mann, 2001; Metsala, 1997, 1999; Storkel & Morrisette, 2002; Walley & Flege, 1999). Considering that individual variations in vocabulary size and in the specific restructuring process could contribute to differences in phonological processing, it was necessary to rule out any potential effect of the participants’ lexical knowledge on their phonological processing skills for the regression analyses employed in the present study. The EVT was selected to measure the expressive vocabulary skill of the children in the MSNH and CA groups.

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Interrater Reliability To determine interrater reliability at the termination of the data collection period, a trained reliability coder, who was a doctoral student of speechlanguage pathology, independently coded data from 40 randomly selected participants (50% of all subjects). This coder calculated the children’s raw scores on all test items, converted them to standard scores, and entered them into a Microsoft Office Excel spreadsheet. The coder and the first author, who were blind to each other’s scoring, conducted an item-byitem comparison of responses for each test administered. Any disagreements in scoring were resolved through discussion by the two individuals. A reliability score was calculated for all variables by dividing the number of agreements by the number of disagreements plus agreements and multiplying by 100. Interrater agreement was 97.6% for response accuracy and 99.0% for raw-score-to-scaled-score conversions. Results

Comparisons of Phonological Processing Skills Across Groups The groups did not differ on chronological age, F(2,77) = .817, p > .05, or

grade, F(2, 77) = .818, p > .05, but did differ significantly on nonverbal intelligence, F(2, 77) = 6.354, p < . 01. Therefore, nonverbal IQ was used as a covariate in all analyses. Group membership served as the independent variable, and standard scores from the seven core tests of the CTOPP served as dependent variables. The three groups’ standard scores for each of the seven measures were compared using a multivariate analysis of covariance (MANCOVA). A MANCOVA was used to guard against the risk of Type I errors when multiple univariate tests were run. Analysis of covariance (ANCOVA) was used for all follow-up pairwise comparisons of groups. Unless otherwise noted, the criterion for statistical significance was set at p ⱕ .05. For pairwise comparisons, significant group differences were reported using Cohen’s d. In behavioral science research, a d value of .5 is considered to be a medium effect size and values of .8 and above are considered to be large effect sizes (Cohen, 1988). The adjusted group means, F values, and effect sizes of seven ANCOVAs are presented in Table 3. Mean standard scores for the seven CTOPP tests for the three groups are shown in Figure 2. Data satisfied the multi-

variate test for the covariance assumption, Box’s M = 43.191, p = .140, and the omnibus MANCOVA test revealed a main effect for group, Wilks’s ␭ = .266, F(14, 140) = 9.401, p < .001. The multivariate effect size was large (␩␳2= .485), showing that more than 45% of the multivariate variance of the dependent variables was explained by the main group effect. Since the MANCOVA yielded a statistically significant main group effect, scores for each phonological measure were submitted to a series of univariate ANCOVAs. Follow-up univariate ANCOVAs revealed significant group differences, with varying effect sizes for all of the phonological measures: Elision, F(2,76) = 38.12, p < .001, ␩␳2 = .501; Blending Words, F(2,76) = 40.49, p < .001, ␩␳2 = .516; Rapid Digit Naming, F(2,76) = 22.54, p < .001, ␩␳2 = .372; Rapid Letter Naming, F(2,76) = 24.23, p < .001, ␩␳2 = .389; Rapid Object Naming, F(2,76) = 13.12, p < .001, ␩␳2 = .257; Nonword Repetition, F(2,76) = 22.64, p < .001, ␩␳2 = .373; and Memory for Digits, F(2,76) = 6.166, p = .003, ␩␳2 = .140. Effect sizes were large for all tests (i.e., ␩␳2 > .25) except Memory for Digits. Larger effect sizes were found for the phonological awareness tests (Blending Words and Elision) than for all other

Table 3

Seven Phonological Processing Measures of the CTOPP for Three Groups and the Results of Multiple ANCOVAs Adjusted M (SE), by group Test Elision Blending Rapid Digit Naming Rapid Letter Naming Rapid Object Naming Nonword Repetition Memory for Digits

CA ( n= 29)

MSNH( n= 21)

DYS(n = 30)

Group F a

␩␳2

11.440 (.339) 10.903 (.280) 10.823 (.361) 10.798 (.353) 10.202 (.397) 11.541 (.378) 10.514 (.412)

8.365 (.389) 7.944 (.321) 9.830 (.414) 9.746 (.405) 9.100 (.455) 8.264 (.433) 9.760 (.472)

7.353 (.320) 7.533 (.264) 7.557 (.341) 7.473 (.334) 7.402 (.375) 8.132 (.357) 8.532 (.389)

38.12** 40.49** 22.54** 24.23** 13.12** 22.64** 6.17*

0.501 0.516 0.372 0.389 0.257 0.373 0.140

Notes. Shown are adjusted means, effect sizes, and F values of analyses of covariance (ANCOVAs). CA, normally hearing group. MSNH, group with mild to moderate sensorineural hearing loss. DYS, group with dyslexia. adf = 2, df = 76. 1 2 *p ⱕ .01. **p ⱕ .001.

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN Figure 2

The Three Groups’ Performance on the CTOPP Subtests

Notes. Error bars represent the standard error of the mean. CTOPP, Comprehensive Test of Phonological Processes. CA, control group. MSNH, group with mild to moderate sensorineural hearing loss. DYS, group with dyslexia. Blending, Blending Words. MemDig, Memory for Digits. NWR, Nonword Repetition. RAN-D, Rapid Digit Naming. RAN-L, Rapid Letter Naming. RAN-O, Rapid Object Naming.

tests of phonological processing on the CTOPP. Subsequent post hoc pairwise t tests were conducted to directly compare means for the three groups for each variable (CA vs. MSNH, CA vs. DYS, and MSNH vs. DYS). Bonferroni correction methods were used to adjust for expected probabilities with multiple comparisons in all t tests. Effects were considered statistically significant at p < .017. The results of the pairwise comparisons are presented in Table 4. Clear differences and similarities were observed between the MSNH and CA groups and the MSNH and DYS groups. First, the MSNH and CA groups differed significantly on both the Elision and Blending Words measures. However, the MSNH group did not differ significantly from the DYS group on either of these phonological awareness tasks (see Figure 2). In line with the current literature, the DYS group outperformed the CA group on all phonological measures with considerably large effect sizes. Second, no significant group differences were found between the MSNH and CA

groups on any of the three measures of rapid naming, but the MSNH group outperformed the DYS group on all rapid naming tasks with large effect sizes (d ranging from 0.82 to 1.25). Third, a mixed pattern of differences between groups was found on the two tests of phonological memory. The MSNH group did not significantly differ from the CA group, but it performed significantly better than the DYS group on the Memory for Digits test. In contrast, the MSNH group’s scores on the Nonword Repetition test were significantly poorer than the CA group’s, but were not significantly different from those of the DYS group. In summary, significant group differences with fairly large effect sizes were observed between children in the MSNH and CA groups for the construct of phonological awareness, replicating findings from previous studies revealing phonological awareness weaknesses in children with hearing loss. Furthermore, children in the MSNH group showed skill levels similar to those of their CA peers on the phonological retrieval construct

of rapid automatized naming. Only on the construct of phonological memory did the MSNH group show disparate patterns of performance, with digit recall scores similar to those of their CA peers and nonword repetition scores similar to those of their DYS peers.

Associations Between Audiologic Background Measures and Phonological Processing Skills First-order partial correlations coefficients were computed within the MSNH group to remove the effect of nonverbal IQ scores (TONI-3) and individual variability in the expressive vocabulary size (EVT). The strength of the correlations was evaluated using guidelines suggested by Cohen (1988), with .10 considered small, .30 moderate, and .50 large. Based on the results of the partial correlation analyses, a set of hierarchical multiple regression analyses were conducted to determine the unique and shared contributions of individual audiologic background factors in predicting scores for phonological processing

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Table 4

Post Hoc Bonferroni Analyses of Mean Score Differences Between Pairs of Groups for CTOPP Phonological Processing Measures Groups compared, by measure

Mean differencea

SE

t

p

Cohen’s d

CA–MSNH CA–DYS MSNH–DYS Blending Words CA–MSNH CA–DYS MSNH–DYS Rapid Digit Naming CA–MSNH CA–DYS MSNH–DYS Rapid Letter Naming CA–MSNH CA–DYS MSNH–DYS Rapid Object Naming

3.075 4.087 1.011

0.532 0.476 0.497

5.78 8.58 2.01

< .001* < .001* .136

1.77 2.35 0.58

1.959 3.369 0.410

0.439 0.392 0.410

6.74 8.59 1.00

< .001** < .001* .960

2.07 2.36 0.29

0.993 3.265 2.272

0.566 0.506 0.529

1.75 6.45 4.29

.251 < .001* < .001*

0.50 1.76 1.22

1.052 3.325 2.273

0.554 0.495 0.518

1.89 6.72 4.39

.185 < .001* < .001*

0.58 1.83 1.25

CA–MSNH CA–DYS MSNH–DYS Nonword Repetition CA–MSNH CA–DYS MSNH–DYS Memory for Digits CA–MSNH CA–DYS MSNH–DYS

1.102 2.799 1.697

0.623 0.557 0.582

1.77 5.03 2.92

.243 < .001* .014*

0.54 1.37 0.82

3.277 3.409 0.132

0.593 0.530 0.554

5.51 5.87 0.06

< .001* < .001* 1.000

1.68 1.60 0.02

0.754 1.982 1.228

0.646 0.577 0.603

1.90 3.44 2.04

.171 .003* .012*

0.43 0.94 0.73

Elision

Notes. CTOPP, Comprehensive Test of Phonological Processes. CA , normally hearing controls (n = 29). MSNH, group with mild to moderate sensorineural hearing loss (n = 21). DYS, group with dyslexia (n = 30). aMean differences are based on the adjusted group means. *Statistically significant p values following Bonferroni correction to experimentwise ␣ of .017.

skills. Because the MSNH group was the focus of interest in the present study, correlation and regression analyses were carried out for this group only. Table 5 shows the partial correlation coefficients (i.e., adjusting for the variance accounted for by nonverbal IQ and vocabulary) for three audiologic background variables: (a) better ear PTA, (b) age at identification of hearing loss, and (c) duration of hearing aid use for the seven phonological processing tasks that

represented the three phonological constructs under study (PA, PM, RAN). As expected, degree of hearing loss (PTA) was moderately and significantly correlated with both PA measures (Elision and Blending Words) and one PM measure (Nonword Repetition): Elision, r = –.402, p = .49; Blending Words, r = –.428, p = .038; and Nonword Repetition, r = –.501, p = .004. Notably, all of the correlations between the better ear PTA and rapid naming tasks were nonsignificant and

weak: Rapid Digit Naming, r = –.078, p = .379; Rapid Letter Naming, r = –.126, p = .310; and Rapid Object Naming, r = –.156, p = .286. Age at identification was significantly, though only mildly, correlated with both PA tasks (Elision, r = –.145, p = .039; Blending Words, r = –.102, p = .021), and moderately correlated with the Nonword Repetition test (r = –.447, p = .032). Again, no significant correlations were found between age at identification and rapid naming measures: Rapid Digit Naming, r = –.138, p = .192; Rapid Letter Naming, r = –.193, p = .221; and Rapid Object Naming, r = –.058, p = .410. Last, the contribution of audiologic background measures to phonological processing ability was examined after the student’s scores on the TONI-3 and the EVT were accounted for. Three audiologic background measures (better ear PTA, age at identification, and duration of hearing aid use) served as independent variables, and three CTOPP composite scores served as the dependent variables in a series of multiple regression analyses shown in Table 6. In Step 1, scores on the TONI-3 and the EVT were entered into the model, and in Step 2, three audiologic variables were forced into the model using the Enter method. The Enter method was selected because the goal of this analysis was to determine which audiologic variables were the most robust predictors of the children’s phonological processing skills. As shown in Table 6, only the model for the PA composite scores had significant predictive values, adjusted ⌬R2 = .282, F(3, 14) = 2.925, p < .05. Specifically, in Step 1, nonverbal IQ and expressive vocabulary accounted for about 6% of the variance of PA composite score, and both of these variables were significant predictors (p < .05). In Step 2, the better

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN Table 5

Pearson’s Correlation Coefficients (r) Computed Within the MSNH Group Between Audiologic Background Measures and the CTOPP Subtests Scores With Nonverbal IQ and Expressive Vocabulary Partialled Out CTOPP Subtests Variables

Elision

Blending words

Better ear pure tone average Age at identification Duration of HA use

–.402* –.145* –.077

–.428* –.102* .140

Rapid Digit Naming

Rapid Letter Naming

Rapid Object Naming

Nonword Repetition

Memory for Digits

–.078 –.138 .063

–.126 –.193 .210

–.156 –.058 .400

–.501** –.447* .055

–.226 –.483 –.003

Note. CTOPP, Comprehensive Test of Phonological Processes. *Correlation was significant at the .05 level (two-tailed). **Correlation was significant at the .01 level (two-tailed).

Table 6

Hierarchical Multiple Regression Analysis on the MSNH group (n = 21), Predicting the Composite Scores on the CTOPP, With Age, Nonverbal IQ, Expressive Vocabulary, and Audiologic Variables as Predictors Regression models Model for phonological awareness composite scores Better ear pure tone average Age at identification Duration of hearing aid use

B (SE)

␤

t

p

⌬R 2

⌬Adj R 2

⌬F a

–.535 (.188) –.197 (.131) .056 (.088)

–.666 .177 .151

–2.849 0.739 0.632

.016* .103 .171

.327

.182

2.655*

.161 (.235) .247 (.164) .105 (.110)

.168 .378 .237

0.686 1.503 0.950

.504 .155 .358

.128

.006

0.956 (n.s.)

–.715 (.446) .438 (.313) –.215 (.210)

–.374 .336 –.243

–1.601 1.400 –1.024

.032 .183 .323

.282

.160

2.120 (n.s.)

Model for rapid naming composite scores Better ear pure tone average Age at identification Duration of hearing aid use Model for phonological memory composite scores Better ear pure tone average Age at identification Duration of hearing aid use

Notes. MSNH, mild to moderate sensorineural hearing loss. CTOPP, Comprehensive Test of Phonological Processes. Only the results for the predictors entered in the Step 2 analysis are shown. aIncreased F value (df = 3, df = 14). 1 2 * p < .05.

ear PTA was the only significant predictor after covarying for the effect of nonverbal IQ and vocabulary. The model accounted for about 30% of additional unique variance in PA composite score, confirming the significant association between PA skills and degree of hearing loss. However, the unique proportions of variance contributed by the variables of age at identification and duration of hearing aid use were not statistically significant in this model. Discussion MSNH is associated not only with lower hearing thresholds, but also dis-

tortion of speech signals and degraded language input, which may affect the development of the phonological representations of spoken words and other phonological processing skills (Delage & Tuller, 2007). In order to elucidate previous clinical observations on the impact of congenital MSNH on the development of phonological processing skills, the present study was conducted (a) to compare the phonological processing skills of children with MSNH to those of children with dyslexia (a developmental reading disability defined, in large part, by deficits in phonological processing) and to those of typically

developing children; and (b) to evaluate potential associations between audiologic background measures (e.g., duration of hearing aid use) and phonological processing skills in children with MSNH. Given that the causal factors associated with mild to moderate peripheral hearing loss are sensory deficits and that the causes of phonological processing deficits in dyslexia are presumed to result from neural network deficits associated with various cortical areas, we expected that greater overall phonological deficits would be observed in children with dyslexia.

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Phonological Awareness The data supported our thesis that impoverished auditory perception influenced by hearing loss may lead to depressed phonological awareness skills. This finding is in line with the hypothesized causal chain in the previous literature, which suggests that metalinguistic manipulations of speech segments become difficult if relevant sound segments are not distinctly specified in the representations of words (Elbro, 1996, 1998; Elbro, Borstrøm, & Petersen, 1998; Fowler, 1991; Foy & Mann, 2001; Griffith & Snowling, 2002; Wesseling & Reitsma, 2001). A lack of distinctness or segmental specificity in phonological representations caused by early auditory deprivation might lead to inefficient segmenting of the phonological dimensions of words, leaving phonological codes insufficiently specified in memory (e.g., Elbro, 1996; Fowler, 1991; Hansen & Bowey, 1994; Metsala, 1997; Snowling, Stackhouse, & Rack, 1986; Swan & Goswami, 1997). In other words, if the integrity of phonological representations is compromised by hearing loss, an individual with MSNH may have difficulty performing the segmental operations needed to develop fully specified auditory representations of some words. The impact of hearing loss on phonological awareness skills was further supported by our data showing a relationship between severity of hearing loss and performance on phonological tasks. Furthermore, age at identification of hearing loss was mildly associated with performance on phonological awareness tasks. However, this relationship was not found for the duration of hearing aid use. This unexpected lack of correlation might be explained by the fact that the children with hearing loss in our sample, who had worn hearing aids binaurally for more than 5 years, may have

reached a plateau in their development of phonological representations.

Phonological Memory Our findings only partially supported the hypothesis that the temporary storage of phonological information would be more efficient if the material to be stored were as distinct or as clear as possible (Service, Maury, & Luotoniemi, 2007). Consistent with data from previous studies (Anderson, 2002; Anderson & Lyxell, 1999), we did not find pronounced deficits in children with MSNH on the phonological memory task of digit recall; this indicated that increased hearing loss is not associated with phonological short-term memory skills in these children. Partial correlations support this finding in that no significant association between hearing status (i.e., PTA) and digit recall was found for the MSNH group beyond what would be predicted by expressive vocabulary and nonverbal IQ. The present data may indicate that phonological memory has the potential to serve a compensatory function for young children with hearing loss. Considering the critical role of verbal memory in various language skills, including vocabulary acquisition, phonological processing, and reading (Gathercole & Baddeley, 1990; Rönnberg, 2003; Service, 1992), it is likely that the more severe the hearing impairment, the more extensively individuals will rely on verbal memory to facilitate both spoken and written language. In contrast to the situation in regard to their intact memory for digits, the MSNH group’s level of performance on the phonological memory tasks for nonword repetition was significantly lower than that of the CA group. The MSNH group’s nonword repetition performance was significantly correlated with better ear PTA and age at identification, suggesting

that children with decreased auditory sensory and environmental advantages will perform more poorly than their peers on tasks that demand high levels of auditory attention such as nonword repetition. These mixed results support the findings of Briscoe et al. (2001) that children with MSNH have diminished nonword repetition but intact digit recall abilities. Clearly, the type of verbal stimuli used in these tasks may have led to different patterns of performance on the two phonological memory tasks (Braden, 1992). Stimuli on the digit recall tasks are separate, contiguous, familiar digit names, while stimuli on the nonword repetition tasks are novel, multisyllabic phonological patterns. The low degree of familiarity of the phonological representations for nonsense words, which have no preexisting phonological counterpart (e.g., burloogugendaplo), places relatively higher demands on phonological memory, execution of motor sequences, and coordination of speech articulation to reproduce these unique phonological sequences (Bruck, 1992; Bruck & Treiman, 1990; Dillon, Burkholder, Cleary, & Pisoni, 2004). Since immediate recall of nonwords is exclusively dependent on accurate speech perception, children with hearing loss may require greater resources for auditory attention, and thus be left with reduced resources for central executive functions that support temporary storage. Thus, it is likely that children with MSNH are challenged by phonological memory tasks that use stimuli void of semantic references. Relationships between verbal memory abilities and hearing loss require more extensive investigation.

Rapid Naming Children’s performance on RAN tasks was also examined, because rapid lexical naming is considered to be a phonological process in that it re-

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PHONOLOGICAL PROCESSING SKILLS OF CHILDREN quires the retrieval of phonological codes from long-term memory (Torgesen et al., 1994) and strongly predicts reading achievement in children with dyslexia (Wolf et al., 2000). No significant differences were found between the CA and MSNH groups on all three RAN tasks. This indicated that the lexical access and retrieval skills of children with hearing loss are preserved in spite of their impaired phonological awareness skills. This finding was supported further by nonsignificant correlations between RAN tasks and all audiologic variables for the MSNH group. Furthermore, the MSNH group consistently outperformed the DYS group on all RAN tasks with substantially large effect sizes. The fact that the children with hearing loss performed significantly better than the children with dyslexia and comparably to the typically developing children on the RAN supports the thesis that the RAN task, much as reading does, is likely to tap into multiple skills that lie beyond the boundaries of phonological processing (Norton & Wolf, 2012). Finally, as shown in other studies (Blair et al., 1985; Briscoe et al., 2001, A. Davis, Wood, Healy, Webb, & Rowe, 1995; Elfenbein, Hardin-Jones, & J. Davis, 1994), both the degree of hearing loss and the age at which hearing loss was identified in children with MSNH were related to their performance on both phonological awareness and phonological memory tasks. While the length of time that children possessed their hearing aids did not correlate with their performance on any of these tasks, this finding was not surprising in light of the fact that duration of possession of a hearing aid is not necessarily reflective of the extent of hearing aid use.

Clinical Implications Impoverished auditory stimulation and perceptual difficulties during the

child’s early years can have a deleterious effect on the development of phonological awareness skills in children with MSNH. Data from the present study and others support this thesis. In fact, in spite of the enormous benefits of early hearing loss identification and early hearing aid use in facilitating the development of speech and language skills in children with MSNH, these children are at great risk of failing to develop the phonological processing skills that are expected for their age and are needed to achieve skilled reading (Marschark, 1997; Marschark & Harris, 1996). Unequivocally understood as a critical dimension for later reading success of hearing students, phonological awareness skills are now receiving more educational attention in regard to students who are deaf and hard of hearing. It is necessary that children with MSNH receive explicit instruction in phonological processing skills (e.g., sound categorization skills) before they begin learning to read. As they learn to read, they should be taught phonemic awareness skills as part of the early decoding of phonetically regular words. Furthermore, given that they are at risk of weaknesses in the domain of phonological processing, children with MSNH should be evaluated regularly in these skill areas until their text-level reading speed and accuracy are well developed and clearly at a level of proficiency appropriate for their age and grade. As evidenced by several studies (Dyer, MacSweeney, Szczerbinski, Green, & Campbell, 2003; LaSasso, Crain, & Leybaert, 2003; LuetkeStahlman & Nielsen, 2003; Trezek & Malmgren, 2005), students who are deaf and hard of hearing can be trained to develop phonological awareness through explicit, intensive, and systematic methods. A growing body of recent literature has also in-

vestigated the clinical efficacy of various alternative strategies such as implementing explicit phonics-based reading curricula supplemented by Visual Phonics for providing phonemic aspects of spoken language (e.g., teaching grapheme-to-phoneme correspondence) and developing phonological awareness skills among students who are deaf and hard of hearing (Beal-Alvarez, Lederberg, & Easterbrooks, 2012; Bergeron, Lederberg, Easterbrooks, Miller, & Connor, 2009; Guardino, Syverud, Joyner, Nicols, & King, 2011; Kyle & Harris, 2011; Narr, 2008; Syverud, Guardino, & Selznick, 2009; Trezek & Malmgren, 2005; Trezek & Wang, 2006; Trezek, Wang, Woods, Gampp, & Paul, 2007). A common observation in these studies is that through explicit instruction using multimodal approaches combined with Visual Phonics, deaf and hard of hearing children can gain visual access to the phonological system of a spoken language and acquire graphemeto-phoneme correspondence, which is known to be an important precursor to later reading skills of readers with hearing loss. Unfortunately, several studies of instructional methods have revealed that most teachers of hard of hearing children do not incorporate direct teaching of phonological awareness into their reading instruction (Hanson, 1989; LaSasso & Mobley, 1997; Nielsen & LuetkeStahlman, 2002; Paul, 1998, 2001), in spite of the evidence that these children follow a developmental trajectory that is similar to that of hearing children when they are learning to read (Hanson, 1989; Paul, 1998, 2001). Furthermore, given the evidence of the core role of phonological knowledge in learning an alphabetic language, such as English, along with evidence that students with MSNH are at high risk of performing more poorly than their normally hearing

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peers who are not predisposed to reading deficits, every effort should be made to ensure that the phonological awareness skills of these children be tested regularly and that explicit instruction in the development of these skills begin prior to when they begin learning to decode words in print.

Limitations of the Present Study The number of subjects in each of the clinical groups in the present study was relatively low. Greater numbers are needed to ensure that these findings are representative of both the MSNH group and the DYS group. Furthermore, scores for the DYS group came from archival data collected in the context of diagnostic evaluations of children who came to a speechlanguage-reading clinic for testing before the present study began, while test data for the children with hearing loss were collected in other settings. Finally, reading scores for the two groups would have helped to clarify the nature of the relationship between phonological processing and reading skills in these groups. References Adams, M. (1990). Beginning to read: Thinking and learning about print. Cambridge, MA: MIT Press. American National Standards Institute. (1996). American national standard: Specification for audiometers. New York, NY: Author. Anderson, U. (2002). Deterioration of the phonological processing skills in adults with an acquired severe hearing loss. European Journal of Cognitive Psychology, 14, 335–352. Anderson, U., & Lyxell, B. (1999). Phonological deterioration in adults with an acquired severe hearing impairment: A deterioration in long-term memory or working memory? Scandinavian Audiology, 28, 241–247. Beal-Alvarez, J., Lederberg, A. R., & Easterbrooks, S. R. (2012). Grapheme-phoneme acquisition of deaf preschoolers. Journal of Deaf Studies and Deaf Education. 17, 39–60. Beitchman, J. H., & Young, A. R. (1997). Learning disorders with a special emphasis on reading disorders: A review of the past 10

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