Search

In the present study, we explored how Age of Acquisition (AoA) of L2 affected brain structures in bilingual individuals. Thirty-six native English speakers who were bilingual were scanned with high resolution MRI. After MRI signal intensity inhomogeneity correction, we applied both voxel-based morphometry (VBM) and surface-based morphometry (SBM) approaches to the data. VBM analysis was performed using FSL's standard VBM processing pipeline. For the SBM analysis, we utilized a semi-automated sulci delineation procedure, registered the brains to an atlas, and extracted measures of twenty four pre-selected regions of interest. We addressed three questions: (1) Which areas are more susceptible to differences in AoA? (2) How do AoA, proficiency and current level of exposure work together in predicting structural differences in the brain? And (3) What is the direction of the effect of AoA on regional volumetric and surface measures? Both VBM and SBM results suggested that earlier second language exposure was associated with larger volumes in the right parietal cortex. Consistently, SBM showed that the cortical area of the right superior parietal lobule increased as AoA decreased. In contrast, in the right pars orbitalis of the inferior frontal gyrus, AoA, proficiency, and current level of exposure are equally important in accounting for the structural differences. We interpret our results in terms of current theory and research on the effects of L2 learning on brain structures and functions.

Developmental dyslexia is a common reading disorder that negatively impacts an individual's ability to achieve literacy. Although the brain network involved in reading and its dysfunction in dyslexia has been well studied, it is unknown whether dyslexia is caused by structural abnormalities in the reading network itself or in the lower-level networks that provide input to the reading network. In this study, we acquired structural magnetic resonance imaging scans longitudinally from 27 Norwegian children from before formal literacy training began until after dyslexia was diagnosed. Thus, we were able to determine that the primary neuroanatomical abnormalities that precede dyslexia are not in the reading network itself, but rather in lower-level areas responsible for auditory and visual processing and core executive functions. Abnormalities in the reading network itself were only observed at age 11, after children had learned how to read. The findings suggest that abnormalities in the reading network are the consequence of having different reading experiences, rather than dyslexia per se, whereas the neuroanatomical precursors are predominantly in primary sensory cortices., (© The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Reading is a learned skill that is likely influenced by both brain maturation and experience. Functional imaging studies have identified brain regions important for skilled reading, but the structural brain changes that co-occur with reading acquisition remain largely unknown. We investigated maturational volume changes in brain reading regions and their association with performance on reading measures. Sixteen typically developing children (5-15 years old, eight boys, mean age of sample=10.06 ± 3.29) received two MRI scans (mean interscan interval=2.19 years), and were administered a battery of cognitive measures. Volume changes between time points in five bilateral cortical regions of interest were measured, and assessed for relationships to three measures of reading. Better baseline performances on measures of word reading, fluency, and rapid naming, independent of age and total cortical gray matter volume change, were associated with volume decrease in the left inferior parietal cortex. Better baseline performance on a rapid naming measure was associated with volume decrease in the left inferior frontal region. These results suggest that children who are better readers, and who perhaps read more than less skilled readers, exhibit different development trajectories in brain reading regions. Understanding relationships between reading performance, reading experience, and brain maturation trajectories may help with the development and evaluation of targeted interventions.

Using a non-speech-specific measure of prosody, rise time perception, Goswami and her colleagues have found that individuals with dyslexia perform significantly worse than nonimpaired readers. Studies have also found that children and adults with specific language impairment were impaired on these tasks. Despite the high comorbidity of these disorders, only one study has assessed rise time sensitivity in children with comorbid reading and oral language difficulties. The authors further examined rise time sensitivity in children with both reading and oral language difficulties. They compared performance on rise time perception tasks between 18 children with reading difficulties, 15 children with combined reading and oral language difficulties, and 17 chronological age-matched controls. The authors found a significant interaction between group and performance on auditory tasks. Further tests revealed that chronological age-matched controls were significantly better on the rise time measures compared to both groups of children with reading difficulties. Performance between the groups of children with reading difficulties did not significantly differ.

Reading is a complex process involving recruitment and coordination of a distributed network of brain regions. The present study sought to establish a methodologically sound evidentiary base relating specific reading and phonological skills to neuro-metabolic concentration. Single voxel proton magnetic resonance spectroscopy was performed to measure metabolite concentration in a left hemisphere region around the angular gyrus for 31 young adults with a range of reading and phonological abilities. Correlation data demonstrated a significant negative association between phonological decoding and normalized choline concentration and as well as a trend toward a significant negative association between sight word reading and normalized choline concentration, indicating that lower scores on these measures are associated with higher concentrations of choline. Regression analyses indicated that choline concentration accounted for a unique proportion of variance in the phonological decoding measure after accounting for age, cognitive ability and sight word reading skill. This pattern of results suggests some specificity for the negative relationship between choline concentration and phonological decoding. To our knowledge, this is the first study to provide evidence that choline concentration in the angular region may be related to phonological skills independently of other reading skills, general cognitive ability, and age. These results may have important implications for the study and treatment of reading disability, a disorder which has been related to deficits in phonological decoding and abnormalities in the angular gyrus., (Copyright © 2012 Elsevier Inc. All rights reserved.)

We examined whether the characteristic impairments of dyslexia are due to a deficit in excluding external noise or a deficit in taking advantage of repeated stimulus presentation. We compared non-impaired adults and adults with poor reading performance on a visual letter detection task that varied two aspects: the presence or absence of background visual noise, and a small or large stimulus set. There was no interaction between group and stimulus set size, indicating that the poor readers took advantage of repeated stimulus presentation as well as the non-impaired readers. The poor readers had higher thresholds than non-impaired readers in the presence of high external noise, but not in the absence of external noise. The results support the hypothesis that an external noise exclusion deficit, not a perceptual anchoring deficit, impairs reading for adults.

The involvement of the left hemisphere occipito-temporal (OT) junction in reading has been established, yet there is current controversy over the region's specificity for reading and the nature of its role in the reading process. Recent neuroimaging findings suggest that the region is sensitive to orthographic familiarity [Kronbichler, M., Bergmann, J., Hutzler, F., Staffen, W., Mair, A., Ladurner, G., Wimmer, H. 2007. Taxi vs. Taksi: on orthographic word recognition in the left ventral occipito-temporal cortex. Journal of Cognitive Neuroscience 19, 1-11], and the present study tested that hypothesis. Using fMRI, the OT region and other regions in the reading network were localized in 28 adult, right-handed participants. The BOLD signal in these regions was measured during a phonological judgment task (i.e., "Does it sound like a word?"). Stimuli included words, pseudohomophones (phonologically familiar yet orthographically unfamiliar), and pseudowords (phonologically and orthographically unfamiliar) that were matched on lexical properties including sublexical orthography. Relative to baseline, BOLD signal in the OT region was greater for pseudohomophones than for words, suggesting that the region is sensitive to orthographic familiarity at the whole-word level. Further contrasts of orthographic frequency within the word condition revealed increased BOLD signal for low- than high-frequency words. Specialization in the OT region for recognition of frequent letter strings may support the development of reading expertise. Additionally, BOLD signal in the OT region correlates positively with reading efficiency, supporting the idea that this region is a skill zone for reading printed words. BOLD signal in the IFG and STG correlates negatively with reading efficiency, indicating that processing effort in these classic phonological regions is inversely related to reading efficiency.

The integrity of phonological representation/processing in dyslexic children was explored with a gating task in which children listened to successively longer segments (gates) of a word. At each gate, the task was to decide what the entire word was. Responses were scored for overall accuracy as well as the children's sensitivity to coarticulation from the final consonant. As a group, dyslexic children were less able than normally achieving readers to detect coarticulation present in the vowel portion of the word, particularly on the most difficult items, namely those ending in a nasal sound. Hierarchical regression and path analyses indicated that phonological awareness mediated the relation of gating and general language ability to word and pseudoword reading ability.

The etiology of variation in reading ability and its relationship to inattention, impulsivity, and general cognitive ability were investigated within a large, population-based sample of 9- to 10-year-old twins. Phenotypic and genetic analyses were performed on word-level reading, full-scale IQ, and measures of inattention and impulsivity derived from the Go-NoGo task (i.e., Go errors and NoGo errors, respectively). Moderate and significant phenotypic correlations were found among reading, inattention and IQ, but not between impulsivity and the other variables. Genetic modeling revealed that genetic and shared environmental influences largely accounted for variation in reading, inattention, and IQ and covariation among them, whereas specific environmental influences contributed primarily to variation in impulsivity. Acting through a common factor, a portion of the genetic influences on reading ability appeared to be shared with influences affecting IQ as well as those affecting inattention. The contribution of phonological awareness to the remaining unique genetic influences on reading was explored through additional analyses. A two-common-factor model was revealed, with a strongly genetic general cognitive ability factor affecting reading, inattention, and IQ, and an equally strongly genetic second common factor, which captured the variability in reading ability that was related specifically to phonological processing. The processes involved in reading, therefore, seem to involve genetic and environmental influences that are part of both a general cognitive system and a system more specific to reading and phonology.

We tested the hypothesis that deficits on sensory-processing tasks frequently associated with poor reading and dyslexia are the result of impairments in external-noise exclusion, rather than motion perception or magnocellular processing. We compared the motion-direction discrimination thresholds of adults and children with good or poor reading performance, using coherent-motion displays embedded in external noise. Both adults and children who were poor readers had higher thresholds than their respective peers in the presence of high external noise, but not in the presence of low external noise or when the signal was clearly demarcated. Adults' performance in high external noise correlated with their general reading ability, whereas children's performance correlated with their language and verbal abilities. The results support the hypothesis that noise-exclusion deficits impair reading and language development and suggest that the impact of such deficits on the development of reading skills changes with age.

In a previous study [Sperling, A. J., Lu, Z. L., Manis, F. R., & Seidenberg, M. S. (2003). Selective deficits in magnocellular processing: A "phantom contour" study. Neuropsychologia, 41, 1422-1429] we found that dyslexic children were relatively slower in processing achromatic phantom contours. The maximum temporal frequency at which they could identify achromatic phantom contours was correlated with reading ability and orthographic skill in particular. Here we investigated whether similar deficits could be identified in adults. Poor readers were chosen who scored below the 25th percentile on either a standardized test of word identification or nonword pronunciation. Good readers were chosen who scored above the 40th percentile on both reading tasks. We replicated the findings of the child study: poor readers had slower processing in the achromatic version of the task, but not in the chromatic version. Achromatic performance correlated with several measures of reading and reading-related skills, including exception word reading and phonological awareness. We discuss the possibility that the deficits may indicate impairment in noise exclusion that is more readily apparent at higher temporal frequencies.

We evaluated signal-noise discrimination in children with and without dyslexia, using magnocellular and parvocellular visual stimuli presented either with or without high noise. Dyslexic children had elevated contrast thresholds when stimuli of either type were presented in high noise, but performed as well as non-dyslexic children when either type was displayed without noise. Our findings suggest that deficits in noise exclusion, not magnocellular processing, contribute to the etiology of dyslexia.

We investigated the relationship between reading and explicit and implicit categorical learning by comparing university students with poor reading to students with normal reading abilities on two categorical learning tasks. One categorical learning task involved sorting simple geometric shapes into two groups according to a unidimensional rule. The sorting rule was easily stated by the participants, consistent with explicit learning, and all participants attained criterion levels of performance. The second task involved the integration of features on different dimensions with a more complex rule that could not be described by participants, even though most could attain criterion levels of performance consistent with implicit learning. Poor readers performed as well as those without reading problems in explicit learning but not in implicit learning. Implicit learning was correlated with word reading, phonological decoding, and orthographic skill, independent of verbal ability. We consider the role of implicit learning in reading, and how a deficit could impair phonological and orthographic representation and processing.

A word-learning task was used to investigate variation among developmental dyslexics classified as phonological and surface dyslexics. Dyslexic children and chronological age (CA)- and reading level (RL)-matched normal readers were taught to pronounce novel nonsense words such as veep. Words were assigned either a regular (e.g., "veep") or an irregular (e.g., "vip") pronunciation. Phonological dyslexics learned both regular and exception words more slowly than the normal readers and, unlike the other groups, did not show a regular-word advantage. Surface dyslexics also learned regular and exception words more slowly than the CA group, consistent with a specific problem in mastering arbitrary item-specific pronunciations, but their performance resembled that of the RL group. The results parallel earlier findings from Manis, Seidenberg, Doi, McBride-Chang, & Petersen [Cognition 58 (1996) 157-195] indicating that surface dyslexics and phonological dyslexics have a different profile of reading deficits, with surface dyslexics resembling younger normal readers and phonological dyslexics showing a specific phonological deficit. Models of reading and reading disability need to account for the heterogeneity in reading processes among dyslexic children.

A technique by Rogers-Ramachandran and Ramachandran [Vis. Res. 38 (1998) 71-77] was adapted to evaluate magnocellular (M) and parvocellular (P) visual processing efficiency, with identical task structure, in normal and dyslexic children. A battery of phonological, orthographic and cognitive tasks was administered to assess reading ability and component reading skills in both groups. For the visual processing experiment, children identified shapes created by patterns of dots flickering in counter-phase. The dots were black and white in the M condition, versus isoluminant red and green in the P condition. A staircase procedure determined the children's threshold flicker rate for shape identification. Dyslexics displayed selectively slower visual processing in the M condition but not in the P condition. Across all subjects, performance in the M condition was correlated with measures of orthographic skill, consistent with previous findings linking M processing and orthographic skill. Within the dyslexic group, processing in the M condition was negatively correlated with level of phonological awareness. The results are not consistent with the argument that dyslexics with phonological impairments suffer from deficits across all sensory modalities, as those children with the poorest phonological awareness displayed magnocellular processing well within the normal range.

We investigated the relationship between dyslexia and three aspects of language: speech perception, phonology, and morphology. Reading and language tasks were administered to dyslexics aged 8-9 years and to two normal reader groups (age-matched and reading-level matched). Three dyslexic groups were identified: phonological dyslexics (PD), developmentally language impaired (LI), and globally delayed (delay-type dyslexics). The LI and PD groups exhibited similar patterns of reading impairment, attributed to low phonological skills. However, only the LI group showed clear speech perception deficits, suggesting that such deficits affect only a subset of dyslexics. Results also indicated phonological impairments in children whose speech perception was normal. Both the LI and the PD groups showed inflectional morphology difficulties, with the impairment being more severe in the LI group. The delay group's reading and language skills closely matched those of younger normal readers, suggesting these children had a general delay in reading and language skills, rather than a specific phonological impairment. The results are discussed in terms of models of word recognition and dyslexia., (Copyright 2000 Academic Press.)

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.

Existing longitudinal data on patients with classical galactosaemia suggests that neurocognitive functioning is impaired and, in isolated case reports, may show a decline in performance over time. The present study explored whether there are long-term changes in cognitive abilities in patients with galactosaemia and whether oral uridine can improve neurocognitive performance. Thirty-five patients (18 males, 17 females), 29 of whom received oral uridine powder at 150 mg/kg per day (divided dose, three times daily), were evaluated over a 2-5-year period with the Woodcock-Johnson Revised Cognitive Abilities Test, three academic achievement tests, and the Beery Test of Visual Motor Integration. Results showed that the uridine cohort and a comparison group that received only dietary restriction made small gains in cognitive performance over the treatment period and the size of the gains did not differ significantly. Seven subjects who started uridine prior to the age of 14 months did not differ significantly in their cognitive test scores at an average age of 3.5 years from a group of older children who had begun treatment at 4.5 years of age. These results provide no support for any developmental or uridine-treatment-related change in cognitive functioning for this sample of galactosaemic subjects.

Phonological awareness and phoneme identification tasks were administered to dyslexic children and both chronological age (CA) and reading-level (RL) comparison groups. Dyslexic children showed less sharply defined categorical perception of a bath-path continuum varying voice onset time when compared to the CA but not the RL group. The dyslexic children were divided into two subgroups based on phoneme awareness. Dyslexics with low phonemic awareness made poorer /b/-/p/ distinctions than both CA and RL groups, but dyslexics with normal phonemic awareness did not. Examination of individual profiles revealed that the majority of subjects in each group exhibited normal categorical perception. However, 7 of 25 dyslexics had abnormal identification functions, compared to 1 subject in the CA group and 3 in the RL group. The results suggest that some dyslexic children have a perceptual deficit that may interfere with processing of phonological information. Speech perception difficulties may also be partially related to reading experience.

This study examined whether there are different subtypes of developmental dyslexia. The subjects were 51 dyslexic children (reading below the 30th percentile in isolated word recognition), 51 age-matched normal readers, and 27 younger normal readers who scored in the same range as the dyslexics on word recognition. Using methods developed by Castles and Coltheart (1993), we identified two subgroups who fit the profiles commonly termed "surface" and "phonological" dyslexia. Surface subjects were relatively poorer in reading exception words compared to nonwords; phonological dyslexics showed the opposite pattern. However, most dyslexics were impaired on reading both exception words and nonwords compared to same-aged normal readers. Whereas the surface dyslexics' performance was very similar to that of younger normal readers, the phonological dyslexics' was not. The two dyslexic groups also exhibited a double dissociation on two validation tasks: surface subjects were impaired on a task involving orthographic knowledge but not one involving phonology; phonological dyslexics showed the opposite pattern. The data support the conclusion that there are at least two subtypes of developmental dyslexia. Although these patterns have been taken as evidence for the dual-route model, we provide an alternative account of them within the Seidenberg and McClelland (1989) connectionist model. The connectionist model accounts for why dyslexics tend to be impaired on both exception words and nonwords; it also suggests that the subtypes may arise from multiple underlying deficits. We conclude that performance on exception words and nonwords is not sufficient to identify the basis of dyslexic behavior; rather, information about children's performance on other tasks, their remediation experiences, and the computational mechanisms that give rise to impairments must be taken into account as well.

A historical group of 45 children (4-18 years) and adults (18-39 years) with classical galactosemia had deficits of cognitive function that were variable and not related to the age at diagnosis or to severity of illness at presentation. There was a trend for patients to score highest on visual processing tasks. The standardized tests of speech and memory skills fell within the same range as the Broad Cognitive Ability score, indicating that the speech and language deficits may be part of a more global set of cognitive impairments. Scores on the Beery Visual Motor Integration and Block Design Tests fell in approximately the same range as other cognitive abilities. In addition, there was a high incidence of abnormality detected on MRI and 12 patients had neurologic symptoms that included ataxia, tremor and dysmetria. These abnormalities did not correlate with the age at diagnosis, severity of illness at presentation or scores on cognitive testing. The pathophysiology of neurologic and neuropsychologic impairments remains unknown. Since these appear to be unrelated to the duration of galactose exposure, other factors impacting on outcome need to be understood so that strategies can be developed to improve what appears to be a global impairment of cognitive function.

In classic galactosemia, long-term neurologic sequelae can include low cognitive functioning and a curious neurologic syndrome with tremors, dysmetria, and ataxia. An abnormal white-matter signal on cerebral magnetic resonance imaging (MRI) is present in almost all patients; some have mild cerebral or cerebellar atrophy and focal white-matter lesions. The present study was undertaken to assess the integrity of myelinated pathways by recording somatosensory evoked potentials. Results were correlated with age at diagnosis, severity of illness, age at evoked potentials, neurologic examination, MRI studies and cognitive outcome as measured by the Woodcock-Johnson Revised Standard Cognitive Battery. Evoked potentials were abnormal in 17 (28%) of 60 patients who had median nerve, and 26 (77%) of 34 patients who had posterior tibial nerve studies. Abnormalities of the central rather than the peripheral nervous system were most common. Evoked potentials correlated with severity of presenting symptoms (P = .011), age at evoked potential testing (P = .029), and presence of focal white-matter lesions on MRI (P = .049). Results of neurophysiologic testing showed no correlation with the Woodcock-Johnson Battery. Patients with classic galactosemia may have abnormal conduction along myelinated pathways that is associated with other central deficits. Myelin, which contains galactose, may be adversely affected in this inborn error of metabolism.

This study was conducted to determine whether there is a genotype/phenotype correlation between aspects of cognitive, neurologic, and ovarian outcome in patients with galactosemia and the Q188R mutation of the galactose-1-phosphate uridyltransferase gene. The results showed that the Q188R mutation was found in 72% of alleles: 38 patients were homozygous and 21 were heterozygous for Q188R; eight patients did not have the mutation. The mean Broad Cognitive score for the group homozygous for Q188R was 75 (SD = 16), which was not statistically different from the outcome for the heterozygous group (mean score, 67; SD = 25) or the negative group (mean score, 88; SD = 21). Tremor, ataxia, and dysmetria were found in 12 subjects, and there was no association with Q188R status. Similarly, there was no association of this mutation with the development of primary amenorrhea (8 subjects) versus secondary amenorrhea (found in 14 women). Our findings suggests that the variability of outcome for patients with classic galactosemia cannot be explained by Q188R status alone, at least with regard to cognitive functioning, presence of neurologic symptoms, and timing of the onset of ovarian failure.

Twenty-one dyslexic children, ages 9-15, were administered a battery of tests on two occasions separated by 2 years to assess the development of word recognition and spelling. The majority of the subjects were receiving intensive small-group instruction and one-on-one tutoring in reading and writing. Correlational and regression analyses supported the assumption that phonological and orthographic processing are distinct but reciprocally related components of word recognition and spelling. However, phonological skill appeared to capture most of the unique variance in word identification for dyslexics and younger normal readers matched on word identification skill. Although the dyslexic children made significant gains over 2 years in overall word identification skill and in aspects of phonological and orthographic processing, they failed to show significant "catch-up" in any component skills relative to age- and reading-level-matched normal readers. In addition, dyslexics made little or no progress on a measure of phonemic analysis, on a decoding task requiring processing at the level of the phoneme, and at spelling words with unusual and irregular orthography. The results are consistent with the hypothesis that dyslexic children have primary deficits in phonological processing of speech and print and secondary deficits in orthographic processing.

Less-skilled readers may experience a processing bottleneck in reading comprehension produced by a failure to automate word recognition. The automaticity hypothesis predicts that training which increases rapid and automatic word recognition will improve comprehension. To date few studies have tested this hypothesis. Our goal was to test the automaticity hypothesis by training dyslexic readers (n=35) to access the meaning of words more rapidly. Training consisted of speeded word games implemented on a microcomputer that provided feedback concerning subjects' speed and accuracy using sound and graphics. Three experimental tasks were administered both before and after training in which trials with trained and untrained stimuli were randomly intermixed. The measures were latency and accuracy of word vocalization, sentence comprehension, and a dual-task procedure designed to measure automaticity. Although pre/post improvement was larger for trained than untrained stimuli, reaction time on the word vocalization and sentence comprehension tasks improved significantly for both trained and untrained stimuli. In contrast, automaticity and sentence comprehension accuracy improved significantly for trained but not untrained stimuli. The training effect in comprehension remained when controlling for increases in word knowledge. The results support the automaticity hypothesis and further suggest that severely disabled readers may benefit from training in automatic word recognition.

The goal of the present study was to ascertain whether developmental dyslexics and their affected parents evinced similar patterns of deficits in word recognition skills. Forty dyslexic children and both their biological parents were administered a battery of experimental measures of phonological and orthographic processing. Deficits in component skills were defined in terms of deviations from the performance of normal readers matched on reading achievement level. Four distinct patterns of deficits were found among both the dyslexics and their parents: a subgroup with a specific deficit in processing phonological codes; a subgroup with a specific deficit in processing orthographic codes; a subgroup with deficits in processing both phonological and orthographic codes; and a subgroup of individuals who did not significantly differ from normal readers at the same reading level in either processing domain. Although limited evidence for familial subgroup concordance was obtained in both the phonological and combined phonological subgroups, no concordance was observed among families classified into the orthographic or reading-achievement equivalent subgroups. It was concluded that all affected family members shared a propensity for a phonological deficit, and that some family members share a fundamental problem in processing orthographic information as well.

A potentially important source of cognitive developmental variance is that associated with basic cognitive-processing efficiency. Discrepant findings from several studies have failed to establish convincingly whether developmental change exists in basic processing efficiency. Employing 2 different experimental tasks, memory and visual scanning, which permit the isolation of a theoretically similar process, that is, search, we examined age effects on the search-processing parameter after analyzing it for convergent and discriminant validity. Each of the 96 subjects at 4 ages (9, 11, 13, and 15 years) completed both experiments. Validity evidence was obtained through a comparison of process and task intercorrelations, which revealed the former to be significantly more related than the latter (p less than .001). Also, significant age effects (p less than .001) were obtained for the search-processing parameter in both tasks, which provides evidence for the development of basic cognitive-processing efficiency.

Two experiments examined whether normal and disabled readers differed in the utilization of rules in a paired associate learning task. Experiment 1 required children to learn symbol-word associates. Children were assigned to one of three conditions: nonrule, consistent rule, or inconsistent rule. When present, the rule was based on semantic opposites. Subjects benefited from having the rule, but disabled readers showed less improvement across four test blocks than both chronological age (CA) controls and reading age (RA) controls, particularly in the inconsistent condition. Experiment 2 required subjects to learn symbol-symbol associations in one of three conditions: nonrule, consistent rule, or inconsistent rule. When present, the rule specified the locations of a subsidiary figure in each symbol according to the pattern top-right, bottom-left. Disabled and normal readers did not differ in the nonrule condition where reliance on visual memory would be an effective strategy. Normal readers were superior to disabled readers in both rule conditions. In addition, disabled readers in the inconsistent rule condition were less able than normal readers to apply the rule in a generalization task where memory demands were reduced. Results supported the hypothesis that disabled readers have greater difficulty than normal readers inducing and/or using rules, particularly when they are inconsistent. It is suggested that difficulties in acquiring or using complex and inconsistent rules may be one important source of problems learning spelling-sound correspondence rules, which in English are complex and inconsistent.

In this paper we apply a developmental model of reading to the question of dyslexic subtypes. Groups of normal readers (n=40) and dyslexic children (n=50), matched on reading level and IQ, were given a comprehensive test battery measuring level of development of visual, phonological, and orthographic skills. As a group, dyslexics deviated from normal readers of equivalent reading achievement primarily in phonological skills (spelling-to-sound translation and phonemic analysis), although limited differences in knowledge of word-specific spellings were also observed. Dyslexics were superior to the younger normal readers in visual processing of print. Analysis of individual data by reference to the reading level control group revealed three major subgroups: a group with a specific deficit in phonological processing of print (52 percent), a group with deficits in processing both the phonological and orthographic features of printed words (24 percent), and a group with phonological deficits in language (8 percent). The remainder of the sample (16 percent) had specific deficits in visual or orthographic processing of print, in spelling, or did not differ from the control group. The data support the view that most developmental dyslexics have a specific language disorder involving some aspect of phonological processing. However, small subgroups with very different configurations of reading and nonreading difficulties may exist as well.

This study addressed the question of whether dyslexic children use qualitatively different word identification processes as compared to normal readers at the same stage of reading acquisition. Fifty-two dyslexic children and reading-age matched normal readers were required to pronounce words and pseudowords designed to tap several word recognition and decoding processes. Performance profiles were compared for the two reading groups at two reading ages. Although an invariant acquisition sequence was observed across reading groups, differences in level of performance between dyslexics and reading-age controls varied as a function of reading age. The performance of the more advanced dyslexics was virtually indistinguishable from normal readers on all measures. In contrast, the younger reading age dyslexics differed from normal readers on several measures of spelling-sound correspondences. However, no reading group differences were observed on measures of word recognition. The results indicated that dyslexics and normal readers at the same reading age use essentially the same processes to recognize words, but may differ in knowledge of correspondence rules.