Training in phonological awareness generalizes to phonological working memory: a preliminary investigation.
Early reading achievement relies on phonological awareness (PA) and phonological working memory (WM). Children with language impairment (LI) have problems with both. Three studies were conducted to determine whether treating PA would also improve phonological WM in preschoolers with LI. Study 1 confirmed that children with specific LI perform more poorly than age-matched peers on both PA and WM tasks. Study 2 showed that when children with and without LI are matched on a nonword WM task, differences between the groups on PA and on a word WM task are no longer statistically significant. In Study 3, sixteen preschool children with LI received intervention targeting PA skills and improved both their PA and WM abilities. These studies support the use of PA instruction to improve basic phonological mechanisms underlying working memory.
Keywords: literacy, language disorder, intervention, preschool children.
Scholars and practitioners alike are by now well aware that children with language impairments are at increased risk for difficulties in learning to read (e.g., Aram, Ekelman, & Nation, 1984; Aram & Nation, 1980; Bishop & Adams, 1990; Gillam & Carlile, 1997; Korngold, Menyuk, Libergott, & Chesnick, 1988; Menyuk & Chesnick, 1997). The relationship between phonological awareness (PA) and early reading achievement has been clearly established for the general population (e.g., see reviews by Adams, 1990; Blachman, 1994; Wagner & Torgesen, 1987)). It is also been well-documented that children with language impairments have delays in phonological awareness abilities (e.g., Bird, Bishop, & Freeman, 1995; Bishop & Adams, 1990; Catts, 1993; Kamhi & Catts, 1986; Kamhi, Lee, & Nelson, 1985; Menyuk & Chesnick, 1997), and intervention studies have shown that we can successfully foster PA skills in preschoolers and kindergartners with both speech and language impairments (e.g., Gillon, 2000, 2002; Laing & Espeland, 2005; Segers & Verhoeven, 2004; van Kleeck, Gillam, & McFadden, 1998).
Phonological awareness, however, is only one of the phonological processing skills known to be important to early decoding. In addition to PA, the contributions of phonological working memory (WM) to early decoding (word attack skill in early reading) have been well established for children who are typically developing, children with reading disorders, and children with language impairments (see Catts & Kamhi, 1999; Goswami & Bryant, 1990; Wagner & Torgesen, 1987 for reviews). Phonological WM has been measured by both word and nonword repetition and span tasks. Of these two kinds of measures, nonword recall tasks are believed to more "purely" reflect phonological working memory, since they must be carried out independent of semantic lexical knowledge (Gathercole, in press; Gathercole & Baddeley, 1990; Henry & Millar, 1991). Studies outside of the area of reading corroborate that children with language impairment perform more poorly than age- and language-matched peers on nonword repetition and nonword span tasks, suggesting that these children have a diminished phonological WM capacity (e.g., Bishop, North, & Donlan, 1996; Dollaghan & Campbell, 1998; Edwards & Lahey, 1998; Ellis Weismer, Tomblin, Zhang, Buckwalter, Chynoweth, & Jones, 2000; Gathercole & Baddeley, 1990; Gillam, Cowan, & Day, 1995; Gray, 2003, 2004; Marton & Schwartz, 2003; Montgomery, 1995, 2000a, 2000b).
As we continue to work to develop interventions that take empirical findings regarding the basic cognitive underpinnings of early decoding into account, these findings might lead us to ask if we should be targeting phonological WM in addition to PA in order to provide the best possible foundation for later early decoding skills in children with language impairments. First, however, we might ask if it is feasible to directly improve phonological WM skills. We know that nonword recall is highly heritable (Bishop et al., 1996) and that it is not readily affected by environmental influences (Alloway, Gathercole, Willis, & Adams, 2004; Campbell, Dollaghan, Needleman, & Janosky, 1997). One possible consequence of these facts is that the phonological memory skills underlying nonword recall may be resistant to treatment (Gathercole, in press).
We are aware of only one study that has trained children in nonword repetition in order to improve phonological WM, and hence early reading ability. The study involved 120 Greek-speaking kindergartners who were assigned randomly to a control or treatment group (Maridaki-Kassotaki, 2002). The treatment lasted for the school year, and the treatment group showed superior performance over the control group on a reading test at the end of first grade. This was only one study, and it was not conducted with children learning the English script. Being left with little empirical guidance on this question, we might ask what guidance theory offers regarding whether or not there is even a need to focus on phonological WM in addition to PA skills.
Two different theoretical positions regarding the relationship between PA and phonological WM appear to offer different answers to this question. Baddeley (2003) refers to these two opposed positions as the general phonological processing hypothesis (Bowey, 2001; Snowling, Chiat, & Hulme, 1991) and the phonological loop hypothesis (Baddeley, Gathercole, & Papagno, 1998; Gathercole, Willis, Emslie, & Baddeley, 1991). The phonological loop hypothesis regarding phonological processing abilities is part of the broader model of working memory, which includes a central executive function and as well as modality-specific functions (of which the phonological loop is one).
The general phonological processing hypothesis purports that both PA and phonological WM rely on a single latent phonological processing ability (see also Gottardo, Stanovich, & Siegel, 1996; Mann & Liberman, 1984; Shankweiler, Crain, Brady, & Macaruso, 1992). Applied to intervention, this would suggest that working on PA should also improve phonological WM. In contrast, the phonological loop hypothesis posits two separable components a temporary storage system and a subvocal rehearsal system that allows for refreshing verbal material. The temporary storage serves to hold verbal information in memory while other cognitive tasks, such as comprehension or the manipulation of the sound structure required in PA tasks, are carried out. The rehearsal system refreshes the verbal material to keep it from fading.
In support of the idea of separable subcomponents in the phonological loop, Baddeley (2003) discusses how PA and nonword repetition each account for unique variance in predicting reading, citing a study by Gathercole, Willis, and Baddeley (1991). However, in this cited study, Gathercole et al. conclude that in addition to reflecting unique variance, PA (using rhyme awareness) and phonological WM appear to also share a general phonological processing component. Other studies have also concluded that, in addition to unique variance, there is also substantial shared or overlapping variance between PA and phonological WM in predicting early reading abilities (e.g., Hansen & Bowey, 1994). So even the phonological loop hypothesis seems to suggest that working on PA and might improve phonological WM, at least to the extent that these two areas share overlapping variance.
We clearly cannot take the idea of adding yet another goal to preschool language therapy lightly. Focusing intervention on a basic underlying cognitive process such as phonological WM would mean that less time would be devoted to working on other, more functional goals. Time and resources are not unlimited in providing services to preschoolers with language impairments, requiring that we choose goals judiciously. Since PA and phonological WM skills do share variance that theory suggests is not spurious, with both skills relying at least in part on the same underlying phonological processing ability, it might be possible to improve both PA and WM by working on just one skill.
Of the two skills, working on PA makes the most sense. In addition to the substantial shared variance, Hansen and Bowey (1994) found that the unique variance in predicting decoding that is accounted for by PA skills is considerably larger (19%) than that accounted for by phonological WM skills (5%). This finding would suggest that, if one had to choose between working on either of these two areas, working on PA would be preferable given its much larger unique contribution to later decoding. We have also accrued a great deal of evidence showing that we can improve PA skills, and in doing so also improve early decoding abilities (see Bus & van IJzendoorn, 1999; and National Reading Panel, 2000, for two meta-analyses of these intervention studies). As noted earlier, there is only one study of Greek-speaking children that has focused on practice with nonword tasks in order to improve children's phonological WM and subsequent reading ability. Finally, PA skills are also directly applied in the classroom setting where, in combination with letter knowledge, they form the basis of phonics training. There is no functional equivalent for nonword span or repetition that contributes directly to success in early decoding.
The goal of the present study, as such, was to provide intervention focused on PA skills in preschoolers with language impairments to determine if doing so would impact not only PA skills (to corroborate previous findings), but also phonological WM as measured by a nonword and word span tasks. As noted earlier, nonword span or repetition tasks are believed to more purely reflect phonological WM than word span tasks that additionally require lexical access (e.g., Baddeley, 2003; Baddeley et al., 1998). For this reason, we included both nonword and word span tasks as outcome measures for our PA training. If PA training improves phonological WM, it should have a greater impact on nonword than on word tasks, since word tasks are supported by lexical access in addition to phonological WM. And finally, we focused on preschoolers given Bus and van IJzendoorn's (1999) conclusion in their meta-analysis that PA training is more effective with preschoolers and kindergartners than with older children.
To begin to explore the impact of training PA on both PA and phonological WM skills, we conducted three studies. In our first study, we compared children with SLI and their age-matched controls on two PA tasks (phoneme awareness and rhyming) and three phonological WM tasks (single-syllable word span, multi-syllable word span, and nonword span). This study was designed to replicate previous research showing the co-occurrence of deficiencies in PA and phonological WM in children with SLI and, in so doing, to validate our measures.
In our second study, we matched children with SLI to children who were typically developing according to their nonword memory span before administering our PA and word span tasks. The primary research question was, "Will children with and without SLI who were matched on nonword recall show performance differences on measures of PA and on word span tasks?" If PA and phonological WM are closely related, we would expect that the group differences on the measures of PA between the children with SLI and the children with typically developing language we expected to find in Study 1 should disappear in Study 2. Furthermore, the magnitude of group differences found in Study 1 should be more reduced in Study 2 for PA skills than for the word span task, since word span tasks rely on lexical access in addition to phonological WM.
In the third study, we trained PA, using both rhyming and phoneme awareness, in children with SLI. Our research question was, "Will training in PA result in improvements in PA and in phonological WM as measured by nonword and word span tasks?" We also asked, "If there are improvements in phonological WM, will these be greater for nonword tasks that rely more exclusively on phonological WM than they are for the word span tasks that rely on lexical access in addition to phonological WM?"
Recall that the first study was designed to replicate previous research showing the co-occurrence of deficiencies in PA and phonological WM in children with SLI and, in so doing, to validate our measures. The primary research question was, "Will children with and without SLI differ on their performance on measures of PA, nonword recall, and word recall?"
Participants: Sixteen children with SLI and 16 typically developing age-matched children participated in the study. The mean age of the children with SLI was 4;6 (years; months) (SD = 0;6) and the mean age of the children in the control group was 4;6 (SD = 0;9). The effect size of the age differences between the groups (measured by Cohen's d) was quite small (.024), indicating 98.5% overlap in the age distributions of the two groups.
The children with SLI had been diagnosed by licensed speech-language pathologists and were enrolled in a private school for children with communication disorders. These students had all been tested within the previous 12 months by licensed speech-language pathologists and/or psychologists, using tests such as The Test of Early Language Development (Hresko, Reid, & Hammill, 1991), the Clinical Evaluation of Language Fundamentals-Preschool (Wiig, Semel, & Secord, 1992), and the Preschool Language Scale-3 (Zimmerman, Steiner, & Pond, 1992). All 16 children in the SLI group had been referred for testing due to teacher and/or parent concerns about their communication, performed more than 1 SD below the mean on one or more of the global standardized language measures, and had nonverbal IQ scores above 90 as documented in special education records.
The children in the age-matched control group were drawn from local preschool programs. None of the children in this group had a history of speech and language disorders, and all were performing at age-level expectations according to teacher report. Procedures: Children completed an informal PA assessment battery designed to measure rhyming and phoneme awareness. Four rhyming tasks and four phoneme tasks were administered. Raw scores from the four rhyming tasks and the four phoneme awareness tasks were combined to create composite rhyming and phoneme awareness scores. A description of the 8 tasks follows:
1. Rhyme identification through oddity. Following MacLean, Bryant, and Bradley (1987), children were shown a series of three pictures and were instructed to point to the picture that did not rhyme with the other two. Children received one training item and ten additional test items.
2. Rhyming identification. Similar to an investigation by Smith and Tager-Flusberg (1982), children were shown a puppet named Jed who liked words that rhymed with his name. After two training items, the children identified whether seven words rhymed with "Jed." Next, children were told that Jed also liked words that rhyme with "kite." The process was repeated with seven more words that either rhymed or did not rhyme with kite ("kite" was repeated as each new word was presented).
3. Rhyme production. Following a procedure by MacLean et al. (1987), children were asked to generate one word that rhymed with single-syllable words spoken by the examiner. A training trial was followed by 10 test items.
4. Rhyme fluency. Children were introduced to a puppet named Matt who also liked words that rhymed with his name. The examiner demonstrated two examples, one real word (cat) and one nonsense word (gat), and then asked children to think of as many words as they could that rhymed with Matt. Children were given a maximum of 30 seconds to complete the task
5. Phoneme judgment and correction. Similar to Chaney (1992), children were introduced to a puppet named Max who sometimes didn't say words right. The examiner showed a series of pictures and said a correct or incorrect version of a single syllable word that was depicted in each picture. The examiner asked children whether Max said the word correctly or not (the judgment task), and then asked the child to show Max how to say the word (correction). Fourteen items were presented after a training item.
6. Initial sound identification. In another task devised by Chaney (1992), children were told that a puppet named Max liked words that started with the same sound as his name. Children heard word pairs ("Max" plus a second word beginning or not beginning with an "m") and were asked to judge whether or not the initial sounds were the same. There was one training item and fourteen test items.
7. Generating initial sounds. Children were introduced to a puppet named Tom who liked words that started with the first sound of his name. The examiner gave children an example of a real word that started with /t/ (tick) and a nonsense word that started with /t/ (toup), then, children had 30 seconds to generate as many words as they could think of that started with the first sound of Tom's name.
8. Identifying initial and final sounds. The examiner presented five words and asked the child to identify the first sound (one began with a vowel) and then presented five more words in which the child was asked to identify the last sound (all consonants). There were no training items on this task.
Children also completed three phonological working memory (WM) tasks. Two were word span tasks (one single-syllable and the other multi-syllable words) and one was a nonword span task. Measures of working memory used an immediate recall format that included lists of phonetically dissimilar single-syllable words, phonetically dissimilar single-syllable non-words, and multisyllable words. Note that we use a nonword span task rather than the nonword repetition task that was pioneered by Baddeley and his colleagues (Baddeley, 2000; Baddeley et al., 1998; Baddeley & Hitch, 1974). Research by Hulme and his colleagues (Hulme, Maughan, & Brown, 1991a; Hulme & Roodenrys, 1995; Roodenrys, Hulme, Alban, Ellis, & Brown, 1994) and Gillam and his colleagues (Gillam et al., 1995; Gillam, Hoffman, & van Kleeck, 1998; Gillam & van Kleeck, 1996) indicates that nonword span tasks are also good measures of phonological WM, and that they are sensitive to working memory differences between children with SLI and their peers who are typically developing. Furthermore, the two kinds of tasks are actually quite similar in their demands on children. Nonword repetition tasks typically increase the number of syllables children are requested to repeat, whereas nonword span tasks use single syllable items, but the number of them children are asked to repeat varies from one to six.
In this study, we measured children's memory spans for single-syllable words (SSW) (bed, cake, doll, gum, feet, nap, pig, soup), single-syllable nonwords (SSNW) (deet, bem, nad, pook, gake, zeeg, kig, fap), and multi-syllable words (MSW) (basket, hammer, scissors, whistle, banana, elephant, kangaroo, policeman) according to working memory procedures established by Cowan (Cowan, 1992; Cowan, Wood, & Borne, 1994) and Hulme (Hulme, Roodenrys, Brown, & Mercer, 1995; Hulme, Snowling, & Quinlin, 1991b; Hulme & Tordoff, 1989). Sequence lengths of two to six items were created in each span condition by sampling at random without replacement. Three lists were created at each list length between 2 and 6 items within each of the span conditions (SSW, SSNW, MSW).
Before span testing began, children listened to and repeated each word or nonword on the test. To eliminate the noise of potential articulatory constraints, the children's production of words or nonwords in isolation was used as the articulatory criterion for the span tasks. On occasion, children produced a word or nonword incorrectly during production testing, then began to produce that item in an adult-like manner as the experiment progressed. When this happened, children were given credit for the correct (adult-like) productions in addition to their more immature productions.
For each span condition, children listened to and repeated three lists of words or nonwords at each list length, beginning with two-item sequences. The list length was increased until children made one or more errors in all three lists at a particular length. Span was calculated as the maximum length at which a participant recalled all three lists correctly, plus 0.33 for each subsequent correct list. This procedure is more sensitive than measuring span as the longest list repeated without error (Cowan, 2001; Hulme et al., 1991a).
Three orders of span conditions (SSW, SSNW, MSW; SSNW, SSW, MSW; and MSW, SSW, SSNW) with separate item orders within the lists were counterbalanced across participants. Within each condition, the lists were spoken in a monotone at a rate of one item per second.
Results and Discussion
A two-way repeated measures ANOVA was computed to evaluate group differences on the PA tasks of rhyming and phoneme awareness. For this and subsequent studies, Eta squared values (indicating the amount of total variance that can be attributed to an effect) are reported for significant main effects and interactions. Cohen's (1988) standardized effect size values (d equals the difference between means divided by the root mean square of their respective standard deviations) are reported for post hoc comparisons.
There was a significant main effect for group (F (1, 30) = 17.02, p < .001, [eta.sup.2] = .983). Neither the Task main effect nor the Group x Task interaction was significant. The children in the SLI group earned significantly lower scores on both the rhyming and phoneme awareness tasks in comparison to their age-matched controls (Table 1), and the group differences were quite large (d = 1.21).
A second two-way, repeated measures ANOVA was calculated to evaluate group differences on the three memory measures (single-syllable words, multi-syllable words, and nonwords span). Significant main effects for Group (F (1, 30) = 38.04, p < .001, [eta.sup.2] = .559] and Task [F (2, 60) = 58.83, p < .001, [eta.sup.2] = .662) were subsumed by a significant Group x Task interaction (F (2, 60) = 4.37, p < .05, [eta.sup.2] = .127). Tukey pairwise comparisons revealed that the children in the SLI group had poorer recall than their age-matched peers on tasks that measured memory for single-syllable words (d = 1.60) and memory for nonwords (d = 1.55). The group differences on tasks that measured memory for multi-syllable words were not significant, and the effect size (d = .61) was in the moderate range (Table 1). Scheffe complex comparisons revealed that the groups differed with respect to the relationships between single-syllable and multi-syllable word recall (Scheffe F (2, 60) = 4.44; p < .05, [eta.sup.2] = .129) (Figure 1). Specifically, children with SLI had larger multi-syllable word spans than single-syllable word spans, but their non impaired peers had smaller multi-syllable word spans than single-syllable word spans. The groups also differed with respect to relationships between multi-syllable word recall and nonword recall (Scheffe F (2, 60) = 4.94; p < .05, [eta.sup.2] = .141). In comparison to their nonimpaired controls, children with SLI evidenced a larger difference between multi-syllable and nonword spans (a span difference of 1.62 vs. a span difference of .85 respectively).
[FIGURE 1 OMITTED]
In comparison to their same age, non-impaired peers, children with SLI performed significantly poorer on our measures of rhyming, phoneme awareness, and working memory. In addition, the magnitude of the group differences was rather large. These results replicated the findings of previous studies showing the co-occurrence of deficiencies in PA and phonological WM in children with SLI, and also served to validate the measures used in the current study.
As indicated earlier, word and nonword recall tasks differ because nonword memory tasks appear to rely more exclusively on phonological WM, while word memory tasks appear to rely on phonological WM and lexical access. We performed a second experiment in which children with and without SLI were matched for nonword recall ability, and were then assessed on the same PA and word span measures that were used in Study 1. The research question in Study 2 was, "Will children with and without SLI who were matched on nonword recall show performance differences on measures of PA and on word span tasks?" To the extent that PA and phonological WM share overlapping variance, we would expect the differences found in Study 1 on PA tasks to disappear when children were matched for phonological WM ability. We would also expect the group differences on word span from Study 1 to disappear in Study 2, to the extent that word span relies on phonological WM. In addition, the magnitude of group differences found in Study 1 should be more reduced in Study 2 for PA skills than for the word span task, since word span tasks rely on both lexical access and phonological WM.
Participants: Twenty children participated in Study 2. We matched 10 children with SLI (none of whom participated in Study 1) with ten typically developing children according to their performance on the nonword span task. In order to obtain 10 closely matched pairs of children, we screened 39 typically developing children from four preschool programs using the nonword span task described in Study 1. The mean nonword recall spans for the two groups were identical (SLI M = 1.463, SD = .280; Memory-matched M = 1.463, SD = .475).
As in Study 1, the children with SLI in Study 2 performed one standard deviation or more below the mean for their age on one or more formal language tests and had nonverbal performance IQ's of 90 or above. The ten children with SLI had a mean age of 5;10 (SD = 1;0). The ten typically developing children who were matched for nonword span had a mean age of 4; 8 (SD = 1;0). A preliminary ANOVA revealed that the children in the control group were significantly younger than the children in the SLI group [F (1, 18) = 7.08, p < .05; d = 1.209]. As in Study 1, none of the typically developing children had a history of speech and language disorders, and all were performing within age-level expectations according to preschool teacher reports.
Procedures. The same tasks from Study 1 were administered in Study 2.
Results and Discussion
When we matched for nonword span, there were no significant group differences on any of the measures of either PA or word span (Table 2). The effect size for rhyming was small (d = .35), with a 76% overlap between the distributions for the two groups. There was also a small effect size (d = .319) for group differences in phoneme awareness, which corresponds to a 78% overlap in the group distributions. In comparison to Study 1, matching for nonword recall reduced the magnitude of group differences in rhyming and phoneme awareness by 136% and 73%, respectively. The magnitude of group differences in single-syllable and multisyllable word span was reduced by 63% and 52%, respectively. These results appear to support a strong relationship between PA and phonological WM. Although phonological WM as measured by nonword span plays an important role in working memory for words, it accounts for somewhat less of the variance in word memory tasks than it does for PA. This finding aligns well with the belief that word tasks may rely more on lexical access than on phonological WM.
In the third study we asked, "Will training in PA result in improvements in phonological WM as measured by a nonword span task?" We also asked, "Will the training also impact word tasks that are less reliant on phonological WM?"
Participants. The sixteen children with SLI who participated in Study 1 received PA training consisting of rhyming and phoneme awareness training. The children attended two classrooms in a school for children with communication disorders. At the beginning of the study, the mean age of the children was 4; 6 (SD = 0;6) At the end of the study, the mean age of the children was 5; 2 (SD = 0;6).
Procedures. The children received 15 minutes of small-group lessons twice each week for two semesters. During the fall semester, children attended a rhyming center for 15 minutes twice each week. Children were led through a series of increasingly difficult rhyming activities progressing from recognition, to imitation, to identification, to judgment, and finally to rhyme creation.
During the spring semester, children attended a phoneme awareness center for 15 minutes twice each week. The purpose of the phoneme awareness activities was to help the children acquire an awareness of sounds at the beginning and end of words. The specific intervention procedures that were used are described in greater detail in van Kleeck et al. (1998).
Results and Discussion
Intervention that focused on rhyming for one semester and on phoneme awareness for a second semester resulted in improved phonological awareness abilities. The effectiveness of this training was reported in van Kleeck et al. (1998). In the current study, we were interested in the impact that training in PA had on two phonological WM tasks, nonword and word span tasks.
We conducted a repeated-measures ANOVA to test changes in various memory spans (single syllable word, multi-syllable word, and nonword) from Time 1 (pretreatment) to Time 2 (postreatment). A significant Type of Memory by Time of Testing interaction [F (2, 30) = 24.49, p < .001] subsumed significant main effects for Type of Memory Span [F (2, 30) = 49.86, p < .001] and Time of Testing [F (1, 15) = 64.69, p < .001). Gains in single syllable word repetition from pretest (M = 2.14, SD = .66) to posttest (M = 2.85, SD = .63) were smaller (d = 1.11) than gains on nonword repetition tasks (d = 3.61) from pretest (M = .67, SD = .39) to posttest (M = 2.19, SD = .46). Notice that multi-syllable memory spans changed very little (d = .21) from pretreatment (M = 2.33, SD = .68) to posttreatment (M = 2.48, SD = .70). These differences imply that PA training impacted nonword span approximately 3 times more than they impacted single-syllable word span. We did not have a control group that did not receive treatment, so it is possible that nonword recall improved more than word recall for reasons that were extraneous to the intervention. However, this possibility is unlikely since our results are consistent with findings reported by Hansen and Bowey (1994) and Metsala (1999). In both of these studies, correlations between nonword repetition tasks and PA tasks were higher than correlations between word recall tasks and PA tasks.
We reported three studies that were designed to replicate previous findings regarding relationships between phonological awareness (PA) and working memory (WM) in a group of children with known problems in phonological processing skills, and to determine if working on PA skills would simultaneously improve phonological WM skills. Our first study replicated findings from other research demonstrating that children with SLI perform more poorly than their age-matched peers on our PA tasks and on our two working memory tasks (nonword and single-syllable word span). These results validated the measurements that were subsequently used in Studies 2 and 3.
In Study 2, children with SLI were matched to their non-impaired peers on the basis of their nonword memory spans. When we matched children with SLI and non-impaired children for nonword memory span, differences between the groups on PA and word span tasks were not statistically significant. Analyses of the group effect sizes revealed that matching on nonword recall accounted for more variance in PA tasks than in word span tasks, thereby suggesting a closer relationship between PA and nonword tasks, than between PA and word tasks.
In Study 3, we measured changes in nonword and word span following training in PA. Children's performance on a series of PA tasks improved statistically, but so did their performance on two phonological working memory measures. In addition, we found that children presented a larger improvement on our nonword recall task than on our single-syllable word recall task. The findings of Study 3 demonstrate the feasibility of using rhyming and phoneme awareness instruction to improve basic phonological mechanisms underlying working memory.
There are two potential explanations for the generalization of PA training to phonological WM. Bowey (1996) and Metsala (1999) found that PA measures and nonword repetition measures shared variance in relation to vocabulary development. These authors suggest that phonological WM and PA tap into a common phonological processing substrate that they refer to as phonological sensitivity. As vocabulary development increases, children reorganize the way they represent sounds in words. From this perspective, instruction on PA tasks impacted phonological sensitivity, which also plays a critical role in phonological WM. One potential problem with this explanation is that is does not account for our finding of greater generalization to nonword recall than to word recall.
The second potential explanation for our results relates to phonological storage mechanisms. Recall that the phonological loop hypothesis posits that working memory involves a temporary storage system and a subvocal rehearsal system that allows for refreshing verbal material. In the rhyming and phoneme awareness tasks that were taught in study 3, children were required to hold sequences of sounds in temporary storage and then to perform other cognitive operations on them (i.e., comparing the first sequence of sounds to other sequences of sounds, thinking of new onset-rhyme combinations, deciding which sound came first in a sequence, and/or finding pictures of words that begin with the same sound as the target word). While the children were completing the PA tasks, they had to hold the original target words in memory. It is likely that these tasks improved the processes inherent in phonological storage, which is thought to play a greater role in nonword recall than word recall (Gathercole, in press). If phonological storage mechanisms were improved through the PA training the children received, it makes sense that they would improve more on nonword recall tasks than on word recall tasks.
It is clear that children with language impairments often have unusual difficulties on phonological working memory tasks and on phonological awareness tasks, and that both of these tasks tap into skills that support reading development. We conducted this study to determine whether it is feasible to directly improve phonological WM skills by working on PA tasks. The clear answer is yes. Weekly PA instruction with preschool-aged children with language impairments resulted in improved phonological awareness and improved phonological working memory.
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Author Contact Information:
Anne van Kleeck, Ph.D.
School of Behavioral and Brain Sciences
Callier Center for Communication Disorders
University of Texas at Dallas
1966 Inwood Road
Dallas, TX 75235-7298
Phone: (214) 905-3147
Ronald B. Gillam, Ph.D.
Communicative Disorders and Deaf Education
1000 Old Main Hill
Utah State University
Logan, UT 84322
LaVae M. Hoffman, Ph.D., CCC-SLP
The University of Oklahoma Health Sciences Center
College of Allied Health
Department of Communication Sciences & Disorders
P.O. Box 26901
Oklahoma City, OK 73190
Phone (405) 271-4214 ext. 46091
Table 1. Mean Performance of Children in the SLI and Age-Matched Groups on the Phonological Awareness Memory Measures Presented in Study 1. SLI CONTROL M SD M SD d Phonological Awareness Rhyming 12.94 5.77 21.69 9.06 .97 Phoneme Awareness 15.19 5.67 22.75 6.30 1.2 Memory Measures Single-Syllable Words 2.25 .65 3.31 .66 1.60 Multi-syllable Words 2.35 .66 2.68 .54 .61 Nonwords .73 .39 1.83 .71 1.55 Table 2 Mean Performance of Children in the SLI and Nonword Memory-Matched Control Groups on the Phonological Awareness and Memory Measured Presented in Study 2 SLI CONTROL M SD M SD d Phonological Awareness Rhyming 27.90 7.51 24.30 10.07 -.35 Phoneme Awareness 23.40 10.33 26.30 9.09 .3 Memory Measures Single-Syllable Words 2.80 1.00 3.23 .72 .59 Multi-syllable Words 2.43 .70 2.66 .79 .29
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|Author:||van Kleeck, Anne; Gilla, Ronald B.; Hoffman, LaVae M.|
|Publication:||The Journal of Speech-Language Pathology and Applied Behavior Analysis|
|Date:||Sep 22, 2006|
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