We raise the new possibility that people diagnosed with developmental dyslexia (DD) are specialized in explorative cognitive search, and rather than having a neurocognitive disorder, play an essential role in human adaptation. Most DD research has studied educational difficulties, with theories framing differences in neurocognitive processes as deficits. However, people with DD are also often proposed to have certain strengths – particularly in realms like discovery, invention, and creativity – that deficit-centered theories cannot explain. We investigate whether these (...) strengths reflect an underlying explorative specialization. We re-examine experimental studies in psychology and neuroscience using the framework ofcognitive search, whereby many psychological processes involve a trade-off between exploration and exploitation. We report evidence of an explorative bias in DD-associated cognitive strategies. High DD prevalence and an attendant explorative bias across multiple areas of cognition suggest the existence of explorative specialization. An evolutionary perspective explains the combination of findings and challenges the view that individuals with DD have a disorder. In cooperating groups, individual specialization is favored when features that confer fitness benefits are functionally incompatible. Evidence for search specialization suggests that, as with some other social organisms, humans mediate the exploration–exploitation trade-off by specializing in complementary strategies. The existence of a system of collective cognitive search that emerges through collaboration would help to explain our species’ exceptional adaptiveness. It also aligns with evidence for substantial variability during our evolutionary history and the notion that humans are adapted not to a particular habitat but to variability itself. Specialization creates interdependence and necessitates balancing complementary strategies. Reframing DD therefore underscores the urgency of changing certain cultural practices to ensure we do not inhibit adaptation. Key improvements would remove cultural barriers to exploration and nurture explorative learning in education, academia, and the workplace, as well as emphasize collaboration over competition. Specialization in complementary search abilities represents a meta-adaptation; through collaboration, this likely enables human groups (as a species and as cultural systems) to successfully adapt. Cultural change to support this system of collaborative search may therefore be essential in confronting the challenges humanity now faces. (shrink)

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French (...) study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia. (shrink)

Dehaene (in Reading in the Brain) reviews and finds support for the phonological deficit hypothesis of developmental dyslexia, which proposes that dyslexics have a basic deficit in processing the constituents of spoken words. This hypothesis can be seen as reflecting three associated claims: a) there is only one basic kind of dyslexia; b) all (or most) dyslexic children have phonological impairments, and c) these phonological impairments cause their dyslexia. We consider each of these claims, and the (...) evidence presented by Dehaene, and conclude that questions remain about all three. Phonological deficits alone seem unlikely to be able to account for the complexity and heterogeneity of developmental dyslexia. (shrink)

Rapid Automatized Naming (RAN) is considered a universal marker of developmental dyslexia (DD) and could also be helpful to identify a reading deficit in minority-language children (MLC), in which it may be hard to disentangle whether the reading difficulties are due to a learning disorder or a lower proficiency in the language of instruction. We tested reading and rapid naming skills in monolingual Good Readers (mGR), monolingual Poor Readers (mPR), and MLC, by using our new version of RAN, (...) the RAN-Shapes, in 127 primary school students (from 3rd to 5th grade). In line with previous research, MLC showed, on average, lower reading performances as compared to mGR. However, the two groups performed similarly to the RAN-Shapes task. On the contrary, the mPR group underperformed both in the reading and the RAN tasks. Our findings suggest that reading difficulties and RAN performance can be dissociated in MLC; consequently, the performance at the RAN-Shapes may contribute to the identification of children at risk of a reading disorder without introducing any linguistic bias, when testing MLC. (shrink)

: If a child’s development is made possible by interaction with his environment, involving an integration of affective and intellectual processes, dyslexia implies multiple cognitive deficits that cause learning difficulties and over time can affect a child’s sense of self. Inattentive behavior due to incomprehension of classroom tasks can cause compounding of gaps in learning that will lead to a lack of foundational skills. Vygotskij underlines how the zone of proximal development determines the difference between the child’s actual level (...) of development and the level of performance that he achieves under the guidance of a teacher, through imitation; the teacher must focus his efforts on identifying what the child is only able to do in collaboration today but will be able to do independently tomorrow. The main means of interaction between the teacher and the dyslexic child is the language that, materialized and objectified in external speech, then distilled into thought as internal speech can arm dyslexic children with foundational skills. Keywords: L.S. Vygotskij; Dyslexia; Language; Learning; Zone of Proximal Development Un approccio alla dislessia evolutiva da una prospettiva Vygotskijana Riassunto: Se lo sviluppo del bambino è reso possibile dall’interazione con il suo ambiente, attraverso l’integrazione di processi affettivi e intellettuali, la dislessia implica molteplici deficit cognitivi con conseguenti difficoltà di apprendimento, che col tempo possono condizionare la percezione che il bambino ha di sé. Il comportamento disattento in classe, dovuto all’incomprensione dei compiti assegnati, può generare un accumulo tale di lacune nell’apprendimento da condurre al mancato sviluppo di abilità fondamentali. Vygotskij sottolinea come la zona di sviluppo prossimale denoti la differenza tra il livello di sviluppo effettivamente raggiunto dal bambino e le prestazioni ottenute sotto la guida di un insegnante, per mezzo dell’imitazione del maestro. Compito dell’insegnante è concentrare gli sforzi al fine di individuare quanto il bambino è in grado di realizzare oggi in collaborazione, che domani sarà in grado di effettuare autonomamente. Il principale mezzo di interazione tra l’insegnante e il bambino dislessico è il linguaggio che, materializzato e oggettivato nel linguaggio esterno, successivamente condensato nel pensiero come linguaggio interno, può consentire ai bambini dislessici lo sviluppo di abilità fondamentali. Parole chiave: L.S. Vygotskij; Dislessia; Linguaggio; Apprendimento; Zona di sviluppo prossimale. (shrink)

Recent findings in autopsy studies, neuroimaging, and neurophysiology indicate that dyslexia is accompanied by fundamental changes in brain anatomy and physiology, involving several anatomical and physiological stages in the processing stream, which can be attributed to anomalous prenatal and immediately postnatal brain development. Epidemiological evidence in dyslexic families led to the discovery of animal models with immune disease, comparable anatomical changes and learning disorders, which have added needed detail about mechanisms of injury and plasticity to indicate that substantial changes (...) in neural networks concerned with perception and cognition are present. It is suggested that the disorder of language, which is the cardinal finding in dyslexic subjects, results from early perceptual anomalies that interfere with the establishment of normal cognitive-linguistic structures, coupled with primarily disordered cognitive processing associated with developmental anomalies of cortical structure and brain asymmetry. This notion is supported by electrophysiological data and by findings of anatomical involvement in subcortical structures close to the input as well as cortical structures involved in language and other cognitive functions. It is not possible at present to determine where the initial insult lies, whether near the input or in high-order cortex, or at both sites simultaneously. (shrink)

Developmental Dyslexia significantly interferes with children’s academic, personal, social, and emotional functioning. Nevertheless, therapeutic options need to be further validated and tested in randomized controlled clinical trials. The use of transcranial direct current stimulation has been gaining ground in recent years as a new intervention option for DD. However, there are still open questions regarding the most suitable tDCS protocol for young people with DD. The current crossover study tested the effectiveness of a short and intensive tDCS protocol, (...) including the long-term effects, as well as the influence of age and neuropsychological processes at baseline on reading improvements. Twenty-four children and adolescents with DD were randomly assigned to receive active tDCS during the first slot and sham tDCS during the second slot or vice versa. Five consecutive daily sessions of left anodal/right cathodal tDCS set at 1 mA for 20 min were administered over the parieto-occipital regions. Reading measures and neuropsychological measures were collected before, immediately after, 1 week and 1 month later the treatment. Our results showed that only the active tDCS condition improved non-word reading speed immediately after and 1 month later the end of the treatment compared with baseline. In addition, the improvement in non-word reading speed was significantly correlated with age and with neuropsychological measures at baseline but only in the active tDCS condition. The current crossover study contributed to enforce previous effects of tDCS, including long-term effects, on non-word reading speed and to understand the effect of age and neuropsychological processes on reading outcomes. Our findings showed that tDCS could be a low-cost and easy-to-implement treatment option with long-term effects for children and adolescents with DD. (shrink)

Some individuals with developmental dyslexia show dissociation in reading skills between languages. The occurrence of dissociation depends on differences in the orthographic characteristics and cognitive demands of languages. This article reports on a Korean–Japanese bilingual and biliterate boy, SJ, with developmental dyslexia, who displayed dissociation between Korean and Japanese in reading and writing accuracy. This study aimed to discuss possible accounts for the profile of his literacy skills from orthographic and cognitive perspectives. To accomplish this aim, (...) we measured SJ’s literacy skills, receptive vocabulary, and cognitive abilities in both Korean and Japanese. Then, we compared his skills to those of monolingual and bilingual children. In terms of accuracy, his reading skills in Korean did not differ significantly from those of bilinguals, although they were lower than Korean monolinguals. His spelling skills were within the average range for Korean monolinguals and bilinguals. In contrast, his reading and writing accuracy levels in Japanese were low compared to both Japanese monolinguals and bilinguals. Moreover, his reading and writing deficits were more remarkable in Japanese kanji. However, his cognitive profile was similar between languages. Specifically, he showed deficits in phonological skills and naming speed in both languages, as well as deficits in visual skills. These results were explained by the facts that visual skills are one of the significant predictors of reading and writing accuracy in Japanese but not in Korean, and that visual skills are a key in learning kanji. Thus, our case, SJ, supports the cognitive account, namely, the idea that different cognitive demands on the development of literacy skills can cause dissociation in literacy skills in bilingual children. (shrink)

Although statistical learning (SL) has been studied extensively in developmental dyslexia (DD), less attention has been paid to other fundamental challenges in language acquisition, such as cross-situational word learning. Such investigation is important for determining whether and how SL processes are affected in DD at the word level. In this study, typically developed (TD) adults and young adults with DD were exposed to a set of trials that contained multiple spoken words and multiple pictures of individual objects, with (...) no information about word-referent correspondences provided within a trial. Nonetheless, cross-trial statistical relations could be exploited to learn word-referent mappings. The degree of within-trial reference uncertainty and the novelty of to-be-learned objects (novel or familiar) were varied under different learning conditions. The results show that across all conditions, young adults with DD were significantly impaired in their ability to exploit cross-trial regularities in co-occurring visual–auditory streams to discover word-referent mappings. Observed impairments were most pronounced when within-trial reference uncertainty was the highest. Subjective measures of knowledge awareness revealed greater development of implicit but not explicit knowledge in the TD group than in the DD group. Together, these findings suggest that the SL deficit in DD affects fundamental language learning challenges at the word level and points to greater reliance on explicit processes due to impaired implicit associative learning among individuals with DD. Such a deficit is likely to influence spoken language acquisition, and in turn affect literacy skills, in people with DD. (shrink)

The noisy computation hypothesis of developmental dyslexia (DD) is particularly appealing because it can explain deficits across a variety of domains, such as temporal, auditory, phonological, visual and attentional processes. A key prediction is that noisy computations lead to more variable and less stable word representations. A way to test this hypothesis is through repetition of words, that is, when there is noise in the system, the neural signature of repeated stimuli should be more variable. The hypothesis was (...) tested in an functional magnetic resonance imaging experiment with dyslexic and typical readers by repeating words twelve times. Variability measures were computed both at the behavioral and neural levels. At the behavioral level, we compared the standard deviation of reaction time distributions of repeated words. At the neural level, in addition to standard univariate analyses and measures of intra-item variability, we also used multivariate pattern analyses (representational similarity and classification) to find out whether there was evidence for noisier representations in dyslexic readers compared to typical readers. Results showed that there were no significant differences between the two groups in any of the analyses despite robust results within each group (i.e., high representational similarity between repeated words, good classification of words vs. non-words). In summary, there was no evidence in favor of the idea that dyslexic readers would have noisier neural representations than typical readers. (shrink)

Although developmental dyslexia (DD) is frequently associate to a phonological deficit, the underlying neurobiological cause remain undetermined. One prominent hypothesis suggests a specific deficit in magnocellular-dorsal (M-D) pathway. Here we investigated the visual M-D and parvocellular-ventral (P-V) pathway in dyslexic and in chronological age and IQ-matched normally reading children by measuring dynamic (frequency doubling illusion) and static stimuli sensibility, respectively. A specific deficit in M-D task was found. Importantly, the M-D deficit was selectively shown in poor phonological decoders. (...) M-D deficit appears to be frequent because 75% of poor pseudo-word readers were at least 1 SD below the mean of the controls. Finally, a replication study by using a new group of poor phonological decoders and reading level controls suggests a possible role of M-D deficit in DD. These results showed that a M-D deficit might impair the sub-lexical mechanisms that are critical for reading development. The possible link between these findings and the oscillatory “temporal sampling” framework is discussed. (shrink)

The present study investigates procedural learning of motor sequences in children with developmental coordination disorder and/or developmental dyslexia, typically-developing children and healthy adults with a special emphasis on the role of the nature of stimuli and the neuropsychological functions associated to final performance of the sequence. Seventy children and ten adults participated in this study and were separated in five experimental groups: TD, DCD, DD, and DCD + DD children and adults. Procedural learning was assessed with a (...) serial reaction time task that required to tap on a specific key as accurately and quickly as possible when stimuli appeared on the screen. Three types of stimuli were proposed as cues: the classical version of the SRTT with 4 squares aligned horizontally on the screen, giving visuospatial cues, and two modified versions, with 4 letters aligned horizontally on the screen and letters at the center of the screen. Reaction times during the repeated and random blocks allowed assessing three phases of learning: global learning, specific learning and retention of the sequence. Learning was considered as completed when RT evolved significantly in the three phases. Neuropsychological assessment involved, among other functions, memory and attentional functions. Our main result was that learning and retention were not influenced by the available cues in adults whereas learning improved with specific cues in children with or without neurodevelopmental disorders. More precisely, learning was not completed with L cues in children with neurodevelopmental disorders. For children with DD, learning was completed with the VS and VS + L cues whereas for children with DCD, learning was completed with combined VS + L cues. Comorbidity between DD and DCD had no more impact on procedural learning than DCD alone. These results suggest that learning depends on the nature of cues available during practice and that cues allowing learning and retention depend on the type of disorder. Moreover, selective attention was correlated with RT during retention, suggesting that this neuropsychological function is important for procedural learning whatever the available cues. (shrink)

Developmental dyslexia hinders reading and writing acquisition of around 5-10 % of the children all over the world. However, little is known about role of prospective memory among dyslexics. Prospective memory is realization of delayed intention. Realization of delayed intention requires self initiated process. The present study explored the role of memory (prospective and retrospective memory), meta-memory and attention among dyslexic’s children. One hundred and fifteen children (51 dyslexics and 64 normal controls) participated in the study. Prospective and (...) retrospective memory questionnaire, everyday attention questionnaire and meta-memory were administered on children. Analysis of variance was used to analyses the data. All the main effects were significant. Some interactions were also found to be significant. Results suggest that dyslexic’s performance on memory (prospective and retrospective memory) was worse than normal control. Meta-memory influences both dyslexics and normal control on prospective and retrospective memory. However, meta-memory affected dyslexics much more than normal control group. Similarly, significant differential effects were observed for simple, difficult and mixed attentional condition among between dyslexics and normal control. Dyslexic’s performance was deteriorated as compared to normal control group. The findings of the study are discussed in the light of the existing literature. Keywords: Meta-memory, Phoneme, Phonological awareness,and Visuo-spatial sktechpad. (shrink)

Although developmental dyslexia is frequently diagnosed in Poland, little knowledge of effective treatment for this disorder is available in Polish society. Remedial teachers for many years have applied traditional methods aimed at correction and compensation for affected cognitive functions and academic skills. Otherwise, although western therapies are regularly advertised in the media, their effectiveness has rarely been subject to scientific investigation. Since the assumptions underlying some approaches are not consistent with current understanding of cognitive function, they may attract (...) negative expert appraisal. Unfortunately, it seems that fashion in dyslexia therapy is resistant to rare expressions of criticism from the scientific community. The purpose of this article is to promote awareness about effective treatment for specific reading disorders. Teachers’ greater understanding in this area should help Polish dyslexic children and their parents, who may be confused by offers of misguided therapy and sharp business practise. It is hoped that this article will clarify the situation. In this review of modern English journal articles, focus is on remedial teaching of reading, and more specifically, support for dyslexic students experiencing difficulties in decoding. Here we are concerned only with therapy in alphabetic languages in which individual speech sounds correspond to letters. Analysis of articles from the last six years leads to the conclusion that the most effective therapy for the reading disorder is training in phonological awareness and consolidation of letter-sound knowledge. However, these skills should be practised in the context of reading. (shrink)

Thomas & Karmiloff-Smith (T&K-S) claim that “Residual Normality” is a priori unlikely, that is, that specific cognitive deficits should not exist in developmental disorders. Here I review evidence that a specific cognitive deficit is at the core of developmental dyslexia and I provide a possible neurological account thereof.

Here we use two filtered speech tasks to investigate children’s processing of slow (.