Naming speed deficits in adults with reading disabilities: a test of the double-deficit hypothesis

The present study investigated the persistent nature of naming speed deficits within the context of the double-deficit hypothesis in a university sample of adults with reading disabilities (RD). Twenty-five university students with RD were compared to 28 typically achieving readers on measures of reading skill, phonological processing, and naming speed. The results indicated that both naming speed and phonological processing deficits characterized the RD group. In a regression analysis, neither naming speed nor phonological processing were important variables in explaining comprehension when reading rate was in the model. The results of the present study are mixed at best and are consistent with earlier conclusions that support for the double-deficit hypothesis of dyslexia remains limited.     

Evaluation of the double-deficit hypothesis subtype classification of readers in Spanish

The double-deficit hypothesis acknowledges both phonological processing deficits and serial naming speed deficits as two dimensions associated with reading disabilities. The purpose of this study was to examine these two dimensions of reading as they were related to the reading skills of 29 Spanish average readers and poor readers (mean age 9 years 7 months) who met the criteria for either single phonological deficit (PD), double deficit (DD), or no deficit. DD children were the slowest readers and had the weakest orthography processing skills. No significant differences were found between PD and DD groups on word and pseudoword reading. Word reading and reading comprehension skills were average or above average in the three studied groups. As in previous studies in transparent orthographies, word reading was not a salient problem for Spanish poor readers, whereas for the DD group, reading speed and orthographic recognition skills were significantly affected.     

Investigating the double-deficit hypothesis of developmental dyslexia in an orthography of intermediate depth

The present study aimed to investigate the double-deficit hypothesis (DDH) in an orthography of intermediate depth. Eighty-five European Portuguese-speaking children with developmental dyslexia, aged 7 to 12, were tested on measures of phonological awareness (PA), naming speed (NS), reading, and spelling. The results indicated that PA and NS were not significantly correlated, and that NS predicts reading fluency (but not reading accuracy and spelling) beyond what is accounted for by PA. Although the majority of the children with developmental dyslexia have double deficit (62.4%), some children have a single phonological deficit (24.7%) or a single NS deficit (8.2%). Children with a double deficit were not more impaired in reading fluency, reading accuracy, and spelling than both single-deficit subtypes. In conclusion, the findings of the present study are partially consistent with the DDH and provide evidence for the multifactorial model of developmental dyslexia. Implications of the DDH for an orthography of intermediate depth are emphasized.

     

Remediating the core deficits of developmental reading disability: a double-deficit perspective

The double-deficit hypothesis (Wolf, 1997; Wolf & Bowers, 1999, this issue) contends that deficits in phonological awareness and deficits in visual naming speed represent two independent causal impediments to reading acquisition for children with developmental reading disabilities (RD). One hundred and sixty-six children with severe RD from 7 to 13 years of age were classified into three deficit subgroups according to a double-deficit framework. A total of 140 children with RD, 84% of the sample, were classified; 54% demonstrated a double deficit (DD), 22% a phonological deficit only (PHON), and 24% a visual-naming speed deficit only (VNS). Diagnostic test profiles highlighted the joint contributions of the two core deficits in depressing written language acquisition. The children in the DD group were more globally impaired than those in the other subgroups, and the VNS group children were the highest achieving and most selectively impaired readers. Following 35 hours of word identification training, sizable gains and significant generalization of training effects were achieved by all subgroups. A metacognitive phonics program resulted in greater generalized effects across the domain of real English words, and a phonological training program produced superior outcomes within the phonological processing domain. The greatest non-word reading gains were achieved by children with only phonological deficits.     

Testing the double-deficit hypothesis in an adult sample

The double-deficit hypothesis of dyslexia posits that reading deficits are more severe in individuals with weaknesses in phonological awareness and rapid naming than in individuals with deficits in only one of these reading composite skills. In this study, the hypothesis was tested in an adult sample as a model of reading achievement. Participants were parents of children referred for evaluation of reading difficulties. Approximately half of all participants reported difficulty learning to read in childhood and a small subset demonstrated ongoing weaknesses in reading. Structural equation modeling results suggest that the double-deficit hypothesis is an accurate model for understanding adult reading achievement. Better reading achievement was associated with better phonological awareness and faster rapid automatized naming in adults. Posthoc analyses indicated that individuals with double deficits had significantly lower reading achievement than individuals with single deficits or no deficits.     

Rapid Naming and Phonemic Awareness: Contributions to Reading,Spelling, and Orthographic Knowledge

The double-deficit hypothesis suggests that deficient skills on two dimensions, rapid naming and phonemic awareness, are associated with poor reading. We studied the reading, spelling, and orthographic skills of Grade 3 children who met our criteria for double asset (DA), single phonological deficit (PD), single naming speed deficit (NSD), and double deficit (DD) groups. Analyses of variance revealed main effects of each factor, oftentimes modified by significant interactions, on the varied achievement measures. All deficit groups performed below the DA children. Compared to children with NSD, children with PD (a) were less accurate decoders, (b) were faster readers, (c) had weaker spelling dictation, and (d) had comparably poor spelling recognition scores. Children with DD showed a mixed pattern of stronger, equal, or weaker skills compared to younger reading level controls.     

Naming speed, phonological awareness, and orthographic knowledge in second graders

Concurrent relationships among measures of naming speed, phonological awareness, orthographic skill, and other reading subskills were explored in a representative sample of second graders. Hierarchical regression analyses revealed that naming speed, as measured by the the rapid automatized naming (RAN) task, accounted for a sizable amount of unique variance in reading with vocabulary and phonemic awareness partialled out. The unique contribution of naming speed to reading was relatively stronger for orthographic skills, whereas the contribution of phonemic skills was stronger for nonword decoding. In further analyses, marked difficulties on a range of reading tasks, including orthographic processing, were seen in a subgroup with a double deficit (slow naming speed and low phonemic awareness) but not in groups with only a single deficit. These findings are broadly consistent with Bowers and Wolf's (1993a, 1993b; Wolf & Bowers, 1999) double-deficit hypothesis of reading disability.     

The role of speed of processing, rapid naming, and phonological awareness in reading achievement

This study investigated the role of speed of processing, rapid naming, and phonological awareness in reading achievement. Measures of response time in motor, visual, lexical, grammatical, and phonological tasks were administered to 279 children in third grade. Measures of rapid object naming, phonological awareness, and reading achievement were given in second and fourth grades. Reading group comparisons indicated that poor readers were proportionally slower than good readers across response time measures and on the rapid object naming task. These results suggest that some poor readers have a general deficit in speed of processing and that their problems in rapid object naming are in part a reflection of this deficit. Hierarchical regression analyses further showed that when considered along with IQ and phonological awareness, speed of processing explained unique variance in reading achievement. This finding suggests that a speed of processing deficit may be an "extraphonological" factor in some reading disabilities.     

Viewing a phonological deficit within a multifactorial model of dyslexia

Participants were administered multiple measures of phonological awareness, oral language, and rapid automatized naming at the beginning of kindergarten and multiple measures of word reading at the end of second grade. A structural equation model was fit to the data and latent scores were used to identify children with a deficit in phonological awareness alone or in combination with other kindergarten deficits. Children with a deficit in phonological awareness in kindergarten were found to be five times more likely to have dyslexia in second grade than children without such a deficit. This risk ratio substantially increased with the addition of deficits in both oral language and rapid naming. Whereas children with one or more kindergarten deficits were at heighten risk for dyslexia, some of these children were found to be adequate or better readers. These results are discussed within a multifactorial model of dyslexia that includes both risk and protective factors.     

Reading comprehension skills of young adults with childhood diagnoses of dyslexia

This study explores the contribution of cognitive processes to comprehension skills in adults who suffered from childhood developmental dyslexia (CD). The performance of adults with CD (ages 17 to 23), chronological age-matched (CA) adults, and reading level-matched (RL) children was compared on measures of phonological processing, naming speed, working memory (WM), general knowledge, vocabulary, and comprehension. The results showed that adults with CD scored lower on measures of phonological processing, naming speed, WM, general knowledge, and vocabulary when compared to CA readers but were comparable to RL children on the majority of process measures. Phonological processing, naming speed, vocabulary, general knowledge, and listening comprehension contributed independent variance to reading comprehension accuracy, whereas WM, intelligence, phonological processing, and listening comprehension contributed independent variance to comprehension fluency. Adults with CD scored lower than CA adults and higher than RL children on measures of lexical processing, WM, and listening comprehension when word recognition and intelligence were partialed from the analysis. In summary, constraints in phonological processing and naming speed mediate only some of the influence of high-order processes on reading comprehension. Furthermore, adults with CD experience difficulties in WM, listening comprehension, and vocabulary independently of their word recognition problems and intellectual ability.     

Developmental dyslexia: Related to specific or general deficits?

The present study was designed to examine the question of whether developmental dyslexia in 12-year-old students at the beginning of secondary education in the Netherlands is confined to problems in the domain of reading and spelling or also is related to difficulties in other areas. In particular, hypotheses derived from theories on phonological processing, rapid automatized naming, working memory, and automatization of skills were tested. To overcome the definition and selection problems of many previous studies, we included in our study all students in the first year of secondary special education in a Dutch school district. Participants were classified as either dyslexic, garden-variety, or hyperlexic poor readers, according to the degree of discrepancy between their word recognition and listening comprehension scores. In addition, groups of normal readers were formed, matching the poor readers in either reading age or chronological age. A large test battery was administered to each student, including phonological, naming, working memory, speed of processing, and motor tests. The findings indicate that dyslexia is associated with deficits in (1) phonological recoding, word recognition (both in their native Dutch and in English as a second language), and spelling skills; and (2) naming speed for letters and digits. Dyslexia was not associated with deficits in other areas. The results suggest that developmental dyslexia, at the age of 12, might be (or might have become) a difficulty rather isolated from deficiencies in other cognitive and motor skills.     

Structural invariance in the associations of naming speed,phonological awareness,and verbal reasoning in good and poor readers: A test of the double deficit hypothesis

The associations of multiple measures of speeded naming, phonological awareness, and verbal intelligence with word reading were examined in 51 poor readers and 74 good readers in third and fourth grade. Structural equation modeling was used to determine the extent to which these two groups exhibited structurally invariant patterns of associations among the constructs. Results revealed that for poor readers, both speeded naming and phonological awarencess were significantly associated with word reading, but verbal intelligence had no association with it. In contrast, for good readers, phonological awareness and verbal intelligence were significantly associated with word reading, but naming speed was not. Findings are discussed in light of the double deficit hypothesis.     

Word processing in dyslexics

Dyslexic children (n=21, mean age=10.2 years) were compared with normal readers of the same age, normal readers of the same reading-age, and poor readers of the same reading-age on measures of phonological decoding and automatic word processing. Three different tasks, varying in phonological demand, were used: a naming task, an auditory-visual matching task, and a lexical decision task. On each task, word-pseudoword profiles were obtained to test phonological decoding skills and unspeeded-speeded profiles were assessed to test automaticity in word processing. Main results indicated that dyslexics have a deficit in automatic phonological decoding skills. The results are discussed within the framework of the phonological deficit and the automatization deficit hypothesis.     

Visual and language processing deficits in compensated and uncompensated college students with dyslexia

In seven experiments, we investigated whether compensated and uncompensated adults with dyslexia show different patterns of deficits in magnocellular visual processing and in language processing tasks. In four visual tasks, we failed to find evidence of magnocellular deficits in either group. However, both groups of adults with dyslexia showed deficits in component language skills, and the degree of reading impairment predicted the nature and extent of these deficits. Uncompensated readers showed deficits in orthographic and especially phonological coding and awareness and were slower on rapid naming. Compensated readers showed word and nonword performance below controls but better than the uncompensated readers. The compensated group was not significantly less accurate than controls on phonological awareness, nor significantly worse overall on rapid naming.     

Naming speed in dyslexia and dyscalculia

In four carefully selected samples of 8- to 10-year old children with dyslexia (but age adequate arithmetic skills), dyscalculia (but age adequate reading skills), dyslexia/dyscalculia and controls a domain-general deficit in rapid automatized naming (RAN) was found for both dyslexia groups. Dyscalculic children exhibited a domain-specific deficit in rapid naming of quantities. This finding is in line with recent assumptions that dyscalculia is associated with a neurobiological deficit in the processing of numerosities. In the dyslexia/dyscalculia group, RAN deficits were additive, that is, the dyslexia/dyscalculia group exhibited the sum of the deficits found in the dyslexia only and dyscalculia only groups. This finding suggests that the cognitive bases of dyslexia and dyscalculia are independent from each other. Within the naming speed paradigm no differential impact of special demands on the executive functions inhibition and shifting was found for any of the four groups.     

The Double-Deficit Theory of Reading Disability Does Not Fit All

The double-deficit theory of reading disability (Wolf & Bowers, 1999) was examined in a sample of 56 reading-disabled and 45 normal-reading elementary school children (aged 8 to 11). As hypothesized, the two groups differed markedly on all phonological analysis tasks and on rapid continuous naming of digits and letters (the double deficits), but they differed as well on orthographic tasks, attention ratings, arithmetic achievement, and all WISC-III factors except perceptual organization. Within the reading-disabled (RD) sample, children in the double-deficit subgroup were no more impaired in reading and spelling than those with a single deficit in phonological analysis, and those with a single deficit in rapid naming were no more impaired than those with neither deficit. Multiple regression analyses suggest that a multiple causality theory of RD is more plausible than a double-deficit theory.     

Semantic effects on word naming in children with developmental dyslexia

Repetition priming was used to examine whether children with dyslexia bias a lexical–semantic pathway when reading words aloud. For the dyslexic group (n = 18, age 9.4–11.8 years), but not for age‐matched controls (n = 18, age 9.2–12.4 years), reaction times when naming pictures were faster after naming the corresponding word. A reading age‐matched control group (n = 24, age 6.8–8.9 years) showed similar priming effects to the children with dyslexia. The magnitude of repetition priming was greater for children with dyslexia with poor nonword reading and slower picture naming. Assuming repetition priming of picture naming is contingent on accessing lexical phonology via semantics, the results suggest less‐skilled normal and disordered readers show a stronger bias towards a lexical– semantic pathway during word reading than skilled readers, and the severity of the phonological representations deficit modulates the strength of that bias in children with dyslexia.     

Word identification and reading disorders in the Spanish language

In this study, a reading-level-match design was used to test the hypothesis that children with reading disability (RD) are characterized by poor phonological skills, and that a developmental lag, as opposed to a specific deficit, will be found in transparent orthographies. Spanish has a transparent orthography and thus children with RD should not show severe difficulties in the use of the phonological route, as in the English language. A sample of 118 participants was selected and organized into three different groups: 40 with RD, 38 normal readers matched in age with the former, and 40 younger normal readers at the same reading level as those with RD. Two experiments were conducted to investigate the effects of lexicality, word frequency, word length, and positional frequency of syllables on lexical decision making and word-naming performance. While the participants were performing the naming task, we recorded what they read to subsequently analyze the form as well as the frequency of naming errors. The present study provides evidence for a deficit in phonological processing in a transparent orthography, particularly in nonword reading, because there were differences between the reading-level-matched groups.     

Classification of Double Deficit Groups Across Time: An Analysis of Group Stability From Kindergarten to Second Grade

The Double Deficit Hypothesis of dyslexia is one approach to classifying students with reading disabilities. The theory offers four distinct groups of readers: (a) average readers, (b) students with phonological deficits, (c) students with naming speed deficits, and (d) students with double deficits: those having both (b) and (c). This study examines the stability of these groups from kindergarten to second grade. An initial sample of 214 students were tested at four time points on measures of rapid automatized naming, phonological awareness, and reading. Latent transition analyses were used to examine the stability of these groups over time. These analyses indicated moderate stability from kindergarten to second grade with the probability of movement between groups being higher in kindergarten and early first grade. The groups differed in reading achievement at each testing time, with the double deficit group obtaining the lowest scores. Implications for early assessment and intervention are discussed.