The effect of varying stimulus context on word-finding ability: Dyslexia further differentiated from other learning disabilities

All learning-disabled children, dyslexic and nondyslexic, were found to be impaired relative to controls on a variety of naming tests: (1) naming pictured objects (visual name), (2) responding with an object name to a definition (auditory definition), (3) completing a sentence with an object name (auditory sentence), or (4) naming palpated objects (tactual). Only on the sentence completion task (auditory sentence), which has been found to be the simplest response mode, were the dyslexic subjects selectively less accurate than the nondyslexic learning disabled, relative to the control group. Although dyslexic subjects tend to circumlocute when naming objects, they did not find it easier, relative to other groups, to give the function rather than the name of objects. Time scores were not in the same direction. The nondyslexic learning-disabled group responded more rapidly than either the dyselxic subjects or controls and made more perceptual errors, findings that may be related to some other factor, possibly the hyperactivity of many of the children in the nondyslexic learning-disabled group. The finding, also, that most of their naming error scores correlate highly with each other as well as with standardized language measures (WISC-R Vocabulary and PPVT), whereas those of the dyslexic and control groups do not, further suggests some underlying pathology to which their language disability is related. Language impairment, then, may be a common factor in all learning disability, dyslexic and nondyslexic, possibly for different reasons.     

Tests that discriminate between dyslexic and other learning-disabled boys

Dyslexic and nondyslexic boys within a single community's learning-disabled class were given a set of tests; performance on each of these tests has been reported to be significantly impaired in other dyslexic children compared to learning-disabled and normal groups. Linear discriminant function analysis revealed that error types rather than levels of performance best separated the carefully matched learning-disabled groups. Slow naming and high percentage of “dysphasic” errors characterized dyslexic boys. Visual temporal-spatial matching and “configuration-deficient” perceptual errors characterized the adequate readers who have other learning disabilities.     

Dyslexic and nondyslexic reading fluency: Rapid automatized naming and the importance of continuous lists

Rapid automatized naming (RAN; Denckla & Rudel, 1976) tasks are consistent predictors of fluency that also discriminate between dyslexic and nondyslexic reading groups. The component processes of RAN that are responsible for its relationship with reading ability remain underspecified, however. We report a study on dyslexic and nondyslexic adult groups that experimentally manipulated RAN formats to elucidate how different components of RAN differentially influence dyslexic and nondyslexic performance. The dyslexic group showed a pervasive deficit in rapid access of individually presented items. Additionally, they showed a significant impairment when multiple items were presented, whereas nondyslexic readers showed marginal facilitation for this format. We discuss the implications of these findings with respect to reading-group differences in reading fluency.     

Rapid silent response to repeated target symbols by dyslexic and nondyslexic children

A previous study demonstrated that naming of repeated colors, objects, letters, and numbers (RAN test) was performed more slowly by dyslexic than by nondyslexic learning disabled children, whereas both groups were slower than controls. A test eliminating the vocal response and requiring “cancellation” of selected verbal targets distinguished the two learning disabled groups from each other only when the targets were triads of numbers or letters, the dyslexic group performing more slowly. Compared even with triad target selection, however, dyslexic children were relatively more impaired on rapid naming (RAN), suggesting a specific relationship of reading to speech or the greater mobilization of language functions which speech requires.     

Personality characteristics of dyslexic and nondyslexic adults

Dyslexic persons have developmental abnormalities in reading, writing, speech, or more than one area. To study differences in personality characteristics 25 each dyslexic and nondyslexic men and women, ranging in age from 21 to 73 years, completed the 300-word Adjective Check List. Analysis indicated significant differences between the two groups on 15 of 37 adjectives. Dyslexic men scored significantly lower than nondyslexic men on the Favorable Adjectives checked, Achievement, Dominance, Intraception, Heterosexuality, Self-confidence, Personal Adjustment, Ideal Self, and Military Leadership scales, and they scored significantly higher than nondyslexic men on the Adapted Child scale. Nondyslexic women scored significantly higher than dyslexic women on the Counseling Readiness and the High Origence/High Intellectence scales and significantly lower on the Nurturance, Nurturing Parent, and Feminine Attributes scales.     

Multi- and unisensory decoding of words and nonwords result in differential brain responses in dyslexic and nondyslexic adults

The present functional magnetic resonance imaging (fMRI) study was designed, in order to investigate the neural substrates involved in the audiovisual processing of disyllabic German words and pseudowords. Twelve dyslexic and 13 nondyslexic adults performed a lexical decision task while stimuli were presented unimodally (either aurally or visually) or bimodally (audiovisually simultaneously).The behavioral data collected during the experiment evidenced more accurate processing for bimodally than for unimodally presented stimuli irrespective of group. Words were processed faster than pseudowords. Notably, no group differences have been found for either accuracy or for reaction times. With respect to brain responses, nondyslexic compared to dyslexic adults elicited stronger hemodynamic responses in the leftward supramarginal gyrus (SMG), as well as in the right hemispheric superior temporal sulcus (STS). Furthermore, dyslexic compared to nondyslexic adults showed reduced responses to only aurally presented signals and enhanced hemodynamic responses to audiovisual, as well as visual stimulation in the right anterior insula.Our behavioral results evidence that the two groups easily identified the two-syllabic proper nouns that we provided them with. Our fMRI results indicate that dyslexics show less neuronal involvement of heteromodal and extrasylvian regions, namely, the STS, SMG, and insula when decoding phonological information. We posit that dyslexic adults evidence deficient functioning of word processing, which could possibly be attributed to deficits in phoneme to grapheme mapping. This problem may be caused by impaired audiovisual processing in multimodal areas.     

Assessing the role of different spatial frequencies in word perception by good and poor readers

Numerous studies indicate that dyslexic and nondyslexic individuals exhibit different patterns of sensitivity to spatial frequency. However, the extension of this effect to normal (nondyslexic) adults of good and poor reading abilities and the role played by different spatial frequencies in word perception have yet to be determined. In this study, using normal (nondyslexic) adults, we assessed reading ability, spatial frequency sensitivity, and perception of spatially filtered words and nonwords (using a two-alternative forced choice paradigm to avoid artifactual influences of nonperceptual guesswork). Good and poor readers showed different patterns of spatial frequency sensitivity. However, no differences in accuracy of word and nonword perception were found between good and poor readers, despite their differences in spatial frequency sensitivity. Indeed, both reading abilities showed the same superior perceptibility for spatially filtered words over nonwords across different spatial frequency bands. These findings indicate that spatial frequency sensitivity differences extend to normal (nondyslexic) adult readers and that a range of spatial frequencies can be used for word perception by good and poor readers. However, spatial frequency sensitivity may not accurately reveal an individual's ability to perceive words.     

Naming fluency in dyslexic and nondyslexic readers: Differential effects of visual crowding in foveal,parafoveal, and peripheral vision

Reading fluency is often indexed by performance on rapid automatized naming (RAN) tasks, which are known to reflect speed of access to lexical codes. We used eye tracking to investigate visual influences on naming fluency. Specifically, we examined how visual crowding affects fluency in a RAN-letters task on an item-by-item basis, by systematically manipulating the interletter spacing of items, such that upcoming letters in the array were viewed in the fovea, parafovea, or periphery relative to a given fixated letter. All lexical information was kept constant. Nondyslexic readers’ gaze durations were longer in foveal than in parafoveal and peripheral trials, indicating that visual crowding slows processing even for fluent readers. Dyslexics’ gaze durations were longer in foveal and parafoveal trials than in peripheral trials. Our results suggest that for dyslexic readers, influences of crowding on naming speed extend to a broader visual span (to parafoveal vision) than that for nondyslexic readers, but do not extend as far as peripheral vision. The findings extend previous research by elucidating the different visual spans within which crowding operates for dyslexic and nondyslexic readers in an online fluency task.     

多动症儿童的智力水平、行为与认知事件相关电位的研究

通过对多动症 (MBD)儿童的智力、行为和认知事件相关电位的分析研究,发现多动症儿童的智力水平正常但均数都低于正常儿童,行为问题的检出率和行为量表指数高于一般正常儿童,反映大脑认知功能的事件相关电位的N2、P3的潜伏期较之正常儿童组均延长,且差异均达到显著性水平。     

阅读障碍儿童语音提取

儿童在提取短时记忆系统的语音信息时,往往会造成部分信息的丢失和回忆量的下降,这种信息丢失量的多少与中央执行系统功能有着密切的联系。为了考察阅读障碍儿童的语音提取特点,挖掘他们记忆失败的本质,使用自由回忆和再认两种任务,考察阅读障碍儿童在无意义音节和汉语词汇上的提取特点,结果发现：（1）阅读障碍儿童在语音提取时,丢失的信息率要显著多于正常儿童,这种丢失可能是由于他们落后的中央执行功能所致;（2）阅读障碍儿童单纯的语音保持能力正常,但不擅长利用语义编码来促进短时记忆效果,而正常儿童却能够较好地利用语义线索。     

Word,nonword, and visual paired associate learning in Dutch dyslexic children

Verbal and non-verbal learning were investigated in 21 8-11-year-old dyslexic children and chronological-age controls, and in 21 7-9-year-old reading-age controls. Tasks involved the paired associate learning of words, nonwords, or symbols with pictures. Both learning and retention of associations were examined. Results indicated that dyslexic children had difficulty with verbal learning of both words and nonwords. In addition, analysis of the errors made during nonword learning showed that both phonological errors and general learning errors were distributed similarly for the reading groups. This suggests that nonword learning in dyslexics is slower, but not qualitatively different from normal readers. Furthermore, no differences were found between the dyslexics and age-matched normal readers on non-verbal learning. Long-term retention of the learned visual-verbal associations (both words and nonwords) was not impaired in dyslexic children as compared to normal readers. Finally, phonological awareness ability was assessed. Dyslexics performed worse than age-matched normal readers, but similar to reading-age controls.     

Paired associate learning in Chinese children with dyslexia

A total of 82 Chinese 11- and 12-year-olds with and without dyslexia were tested on four paired associate learning (PAL) tasks, phonological awareness, morphological awareness, rapid naming, and verbal short-term memory in three different experiments. Experiment 1 demonstrated that children with dyslexia were significantly poorer in visual-verbal PAL than nondyslexic children but that these groups did not differ in visual-visual PAL performance. In Experiment 2, children with dyslexia had more difficulties in transferring rules to new stimuli in a rule-based visual-verbal PAL task as compared with children without dyslexia. Long-term retention of PAL was not impaired in dyslexic children across either experiment. In Experiment 3, rates of visual-verbal PAL deficits among children with dyslexia were all at or above 39%, the highest among all cognitive deficits tested. Moreover, rule-based visual-verbal PAL, in addition to morphological awareness and rapid naming ability, uniquely distinguished children with and without dyslexia even with other metalinguistic skills statistically controlled. Results underscore the importance of visual-verbal PAL for understanding reading impairment in Chinese children.     

Unilateral implicit motor learning deficit in developmental dyslexia

It has been suggested that developmental dyslexia involves various literacy, sensory, motor skill, and processing speed deficits. Some recent studies have shown that individuals with developmental dyslexia exhibit implicit motor learning deficits, which may be related to cerebellar functioning. However, previous studies on implicit motor learning in developmental dyslexics have produced conflicting results. Findings from cerebellar lesion patients have shown that patients' implicit motor learning performance varied when different hands were used to complete tasks. This suggests that dyslexia may have different effects on implicit motor learning between the two hands if cerebellar dysfunction is involved. To specify this question, we used a one-handed version of a serial reaction time task to compare the performance of 27 Chinese children with developmental dyslexics with another 27 age-matched children without reading difficulties. All the subjects were students from two primary schools, Grades 4 to 6. The results showed that children with developmental dyslexic responded more slowly than nondyslexic children, and exhibited no implicit motor learning in the condition of left-hand response. In contrast, there was no significant difference in reaction time between two groups of children when they used the right hand to respond. This finding indicates that children with developmental dyslexia exhibited normal motor skill and implicit motor learning ability provided the right hand was used. Taken together, these results suggested that Chinese children with developmental dyslexia exhibit unilateral deficits in motor skill and implicit motor learning in the left hand. Our findings lend partial support to the cerebellar deficit theory of developmental dyslexia.     

Copying skills in relation to word reading and writing in Chinese children with and without dyslexia

Because Chinese character learning typically relies heavily on rote character copying, we tested independent copying skill in third- and fourth-grade Chinese children with and without dyslexia. In total, 21 Chinese third and fourth graders with dyslexia and 33 without dyslexia (matched on age, nonverbal IQ, and mother’s education level) were given tasks of copying unfamiliar print in Vietnamese, Korean, and Hebrew as well as tests of word reading and writing, morphological awareness, rapid automatized naming (RAN), and orthographic processing. All three copying tasks distinguished dyslexic children from nondyslexic children with moderate effect sizes (.67-.80). Zero-order correlations of the three copying tasks with dictation and reading ranged from .37 to .58. With age, Raven’s, group status, RAN, morphological awareness, and orthographic measures statistically controlled, the copying tasks uniquely explained 6% and 3% variance in word reading and dictation, respectively. Results suggest that copying skill itself may be useful in understanding the development and impairment of literacy skills in Chinese.     

Pupillary and heart rate reactivity in children with minimal brain dysfunction

This study attempted to replicate and extend previous findings on autonomic arousal and responsivity in children with diagnoses of minimal brain dysfunction (MBD). Pupil size, heart rate, skin conductance, and skin temperature were recorded from 32 MBD and 45 control children during a session that included presentation of visual stimuli, simple reaction time (RT), a cold pressor procedure, and rest periods. The MBD children were tested both off and on clinical dosages of stimulant drugs in a crossover design. Evidence of higher than normal arousal levels in the unmedicated MBD Ss was obtained from resting skin conductance and, more tenuously, from pupil size. Lower phasic responsivity in the MBD children was evidenced by slower RT, less cardiac deceleration to both light and RT stimuli, and smaller pupil dilation to the RT stimuli. Spontaneous pupillary constrictions during rest periods, presumably indicating drowsiness, were observed about equally in MBD and control children. Stimulant drugs raised arousal levels but did not reverse the responsivity deficits. The lower phasic reactivity in the MBD group and the effects of stimulant drugs on arousal indices confirm earlier reports. The finding of higher arousal in drug-free MBD children is incompatible with the low arousal hypothesis of MBD but is consistent with a previous report of the effects of a stimulating environment on these children.This work was supported in part by a grant from the Ittleson Family Foundation. The authors thank Frank Abate for technical assistance.     

Developmental and acquired dyslexia: A comparison

Jorm (1979a) has drawn attention to similarities between developmental dyslexia and acquired deep dyslexia, an analogy which has been criticized by A. W. Ellis (1979). A series of three experiments compared the two syndromes, using the techniques applied by Patterson and Marcel (1977) to adult deep dyslexics, to study a group of 15 boys suffering from developmental dyslexia. Patterson and Marcel's patients were able to perform a lexical decision task but showed no evidence of phonemic encoding of nonwords; our dyslexic children performed this task very slowly and with reduced accuracy but showed clear evidence of phonemic coding of the nonword items. Patterson and Marcel observed that their patients could not read out orthographically regular nonwords; our dyslexic children were able to do this task, although more slowly and somewhat less accurately than their chronological age or reading age controls. Finally, Patterson and Marcel observed that highly imageable words were more likely to be read correctly than words of equal frequency but low imageability; we observed a similar effect in both our dyslexic group and in their reading age controls. This implies that the imageability effect may not be peculiar to dyslexics but may be characteristic of normal reading under certain conditions. It is concluded that developmental dyslexics differ from the patients studied by Patterson and Marcel in demonstrating a pattern of reading which, though slow, is qualitatively similar to the reading of normal readers of a younger age. As such, our results do not support Jorm's position.     

Book Reviews

There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.     

Long-term learning in dyslexic children

There is now extensive evidence that the learning processes of dyslexic children show some abnormalities, generally consistent with failure to completely automatise skills. Two studies are reported in which a group of adolescent dyslexic children and a group of normal children matched for age and IQ undertook long-term training on a keyboard spatial task and a choice reaction task respectively. It was concluded that, following extended training, the dyslexic children had normal “strength” of automatisation (as assessed by resistance to unlearning, by ease of relearning after one year, and by dual task performance) but that their initial and their final performance (as assessed by speed and accuracy) were impaired. The results are consistent with the hypothesis that dyslexic children suffer from cerebellar deficit.     

Cognitive profiles and deviation patterns of dyslexic children.

Cognitive profiles of 20 dyslexic children were examined using a battery of neuropsychological tests. Their ages ranged from 90 to 114 mo. (M = 106.6 mo.). Intelligence and reading comprehension were normal, but the subjects had specific problems in decoding written material. These subjects were matched with a control group of same age, sex, and sociocultural status. The dyslexic children presented specific patterns of response on WISC-R subtests and failed a battery of cognitive tests examining subcomponents of reading. For each child, a deviation score was computed which represented the imbalance among the different cognitive functions. Greater imbalance was observed among the dyslexic children in development of cognitive functions than among the normal children.     

Are there qualitative differences in reading behavior between dyslexics and normal readers?

This study asked whether the reading behavior of dyslexics differs qualitatively from that of normal children. Thirty-seven children who had been identified is dyslexic (mean age 11 years, 9 months) were matched with 37 normal readers (mean age 8,6) on ability to read regular words. The dyslexics' and normals' levels of performance on nonsense words and exception words were strikingly close. Also, patterns of individual differences were similar for the two groups. The results suggest that these dyslexics are delayed in the development of both spelling-sound rules and word specific associations. They do not support the view that dyslexics have a specific deficit in the use of spelling-sound rules, or that dyslexics show more extreme individual differences than do normal readers.