Rapid processing of letters,digits and symbols: what purely visual‐attentional deficit in developmental dyslexia?

Visual‐attentional theories of dyslexia predict deficits for dyslexic children not only for the perception of letter strings but also for non‐alphanumeric symbol strings. This prediction was tested in a two‐alternative forced‐choice paradigm with letters, digits, and symbols. Children with dyslexia showed significant deficits for letter and digit strings but not for symbol strings. This finding is difficult to explain for visual‐attentional theories of dyslexia which postulate identical deficits for letters, digits and symbols. Moreover, dyslexics showed normal W‐shaped serial position functions for letter and digit strings, which suggests that their deficit is not due to an abnormally small attentional window. Finally, the size of the deficit was identical for letters and digits, which suggests that poor letter perception is not just a consequence of the lack of reading. Together then, our results show that symbols that map onto phonological codes are impaired (i.e. letters and digits), whereas symbols that do not map onto phonological codes are not impaired. This dissociation suggests that impaired symbol‐sound mapping rather than impaired visual‐attentional processing is the key to understanding dyslexia.     

Covert reading of letters in a case of global alexia

This study describes the case of a global alexic patient with a severe reading deficit affecting words, letters and Arabic numbers, following a left posterior lesion. The patient (VA) could not match spoken letters to their graphic form. A preserved ability to recognize shape and canonical orientation of letters indicates intact access to the representation of letters and numbers as visual objects. A relatively preserved ability to match lowercase to uppercase letters suggests partially spared access to abstract letter identities independently of their visual forms. The patient was also unable to match spoken letters and numbers to their visual form, indicating that she could not access the graphemic representations of letters from their phonological representations. This pattern of performance suggests that the link between graphemic and phonological representations is disrupted in this patient. We hypothesize that VA’ residual reading abilities are supported by the right hemisphere.     

Which children benefit from letter names in learning letter sounds?

Typical U.S. children use their knowledge of letters' names to help learn the letters' sounds. They perform better on letter sound tests with letters that have their sounds at the beginnings of their names, such as v, than with letters that have their sounds at the ends of their names, such as m, and letters that do not have their sounds in their names, such as h. We found this same pattern among children with speech sound disorders, children with language impairments as well as speech sound disorders, and children who later developed serious reading problems. Even children who scored at chance on rhyming and sound matching tasks performed better on the letter sound task with letters such as v than with letters such as m and h. Our results suggest that a wide range of children use the names of letters to help learn the sounds and that phonological awareness, as conventionally measured, is not required in order to do so.     

The relationship between auditory temporal processing,phonemic awareness,and reading disability

Recent research suggests an auditory temporal deficit as a possible contributing factor to poor phonemic awareness skills. This study investigated the relationship between auditory temporal processing of nonspeech sounds and phonological awareness ability in children with a reading disability, aged 8-12 years, using Tallal's tone-order judgement task. Normal performance on the tone-order task was established for 36 normal readers. Forty-two children with developmental reading disability were then subdivided by their performance on the tone-order task. Average and poor tone-order subgroups were then compared on their ability to process speech sounds and visual symbols, and on phonological awareness and reading. The presence of a tone-order deficit did not relate to performance on the order processing of speech sounds, to poorer phonological awareness or to more severe reading difficulties. In particular, there was no evidence of a group by interstimulus interval interaction, as previously described in the literature, and thus little support for a general auditory temporal processing difficulty as an underlying problem in poor readers. In this study, deficient order judgement on a nonverbal auditory temporal order task (tone task) did not underlie phonological awareness or reading difficulties.     

Direct visual access in reading for meaning

Two experiments examined whether phonological receding is an obligatory stage in reading for meaning or whether direct access to a word's semantic representation is the general rule. The first study demonstrated that the time to make a semantic decision about a pair of words was much more delayed by misspelling than was the time to make a phonological one. The second study investigated the effect of varying the syllabic length of a word on reaction time in a category decision task. While reaction time varied with the semantic difficulty of the category decision, it generally proved invariant with respect to syllabic length. It is argued that reading for meaning generally uses a direct route from visual form to semantic representation.     

Automatic activation of phonological information in reading: Evidence from the semantic relatedness decision task

A semantic relatedness decision task was used to investigate whether phonological recoding occurs automatically and whether it mediates lexical access in visual word recognition and reading. In this task, subjects read a pair of words and decided whether they were related or unrelated in meaning. In Experiment 1, unrelated word-homophone pairs (e.g., LION-BARE) and their visual controls (e.g., LION-BEAN) as well as related word pairs (e.g., FISH-NET) were presented. Homophone pairs were more likely to be judged as related or more slowly rejected as unrelated than their control pairs, suggesting phonological access of word meanings. In Experiment 2, word-pseudohomophone pairs (e.g., TABLE-CHARE) and their visual controls (e.g., TABLE-CHARK) as well as related and unrelated word pairs were presented. Pseudohomophone pairs were more likely to be judged as related or more slowly rejected as unrelated than their control pairs, again suggesting automatic phonological recoding in reading.     

Letter names and phonological awareness help children to learn letter-sound relations

Two experimental training studies with Portuguese-speaking preschoolers in Brazil were conducted to investigate whether children benefit from letter name knowledge and phonological awareness in learning letter-sound relations. In Experiment 1, two groups of children were compared. The experimental group was taught the names of letters whose sounds occur either at the beginning (e.g., the letter /be/) or in the middle (e.g., the letter /‘eli/) of the letter name. The control group was taught the shapes of the letters but not their names. Then both groups were taught the sounds of the letters. Results showed an advantage for the experimental group, but only for beginning-sound letters. Experiment 2 investigated whether training in phonological awareness could boost the learning of letter sounds, particularly middle-sound letters. In addition to learning the names of beginning- and middle-sound letters, children in the experimental group were taught to categorize words according to rhyme and alliteration, whereas controls were taught to categorize the same words semantically. All children were then taught the sounds of the letters. Results showed that children who were given phonological awareness training found it easier to learn letter sounds than controls. This was true for both types of letters, but especially for middle-sound letters.     

Evidence for a specific cross-modal association deficit in dyslexia: an electrophysiological study of letter-speech sound processing

The phonological deficit theory of dyslexia assumes that degraded speech sound representations might hamper the acquisition of stable letter-speech sound associations necessary for learning to read. However, there is only scarce and mainly indirect evidence for this assumed letter-speech sound association problem. The present study aimed at clarifying the nature and the role of letter-speech sound association problems in dyslexia by analysing event-related potentials (ERP) of 11-year-old dyslexic children to speech sounds in isolation or combined with letters, which were presented either simultaneously with or 200 ms before the speech sounds. Recent studies with normal readers revealed that letters systematically modulated speech sound processing in an early (mismatch negativity or MMN) and late (Late Discriminatory Negativity or LDN) time-window. The amplitude of the MMN and LDN to speech sounds was enhanced when speech sounds were presented with letters. The dyslexic readers in the present study, however, did not exhibit any early influences of letters on speech sounds even after 4 years of reading instruction, indicating no automatic integration of letters and speech sounds. Interestingly, they revealed a systematic late effect of letters on speech sound processing, probably reflecting the mere association of letters and speech sounds. This pattern is strongly divergent from that observed in age-matched normal readers, who showed both early and late effects, but reminiscent of that observed in beginner normal readers in a previous study (Froyen, Bonte, van Atteveldt & Blomert, 2009). The finding that the quality of letter-speech sound processing is directly related to reading fluency urges further research into the role of audiovisual integration in the development of reading failure in dyslexia.     

Eye movements when reading words with $YMβOL$ and NUM83R5: There is a cost

Recent evidence from masked priming experiments has revealed that readers regularize letter-like symbols and letter-like numbers into their corresponding base letters with minimal processing cost. However, one open question is whether the same pattern occurs when these items are presented during normal silent reading. In the present study, we respond to this question in an eye-movement experiment that included sentences with words that had symbols and numbers as letters, as in “YESTERDAY I SAW THE SECRE74RY WORKING VERY HARD”. Results revealed that there is a greater reading cost associated with letter-by-number replacements than with letter-by-symbol replacements, especially when the replaced letters occur at the beginning of the word. We examine the implications of these findings for models of visual word recognition and reading.     

Linguistic semantic agraphia: A dissociation of the lexical spelling system from semantics

Two spelling systems have been described. The phonological system transcodes speech sounds to letters and is thought to be useful for spelling regular words and pronounceable nonwords. Although the second system, the lexical-semantic system, is thought to use visual word images and meaning to spell irregular words, it is not known if this system is dependent on semantic knowledge. We used a homophone spelling test to examine the lexical-semantic system in five patients. The patients were asked to spell individual homophones (doe or dough) using the context of a sentence. Semantically incorrect and correct homophones were spelled equally well, whether they were regular or irregular. These results demonstrate that an irregular word may be spelled without knowledge of the word's meaning. Therefore, the lexical system can be dissociated from semantic influence.     

The cognitive and neurological basis of developmental dyslexia: a theoretical framework and review.

It is argued that developmental dyslexics have difficulty in accessing the meaning of written words via phonological recoding, although they can successfully access meaning by a direct visual route. This difficulty with phonological recording is explained in terms of a short-term memory deficit. It is suggested that developmental dyslexia is a genetically-based dysfunction of the inferior parietal lobule and evidence is reviewed that this region is important in both reading and short-term memory. Implications for remedial instruction are discussed.     

Sentence reading: do we make use of orthographic cues in homophones?

Starting from the finding that currently phonological models of visual word processing predominate, we examined what happened when important morphological information is disclosed in the orthography but not in the phonology. To do so, we made use of a peculiarity in Dutch. In this language, some forms of the present and the past tense of verbs are homophones or homographs. This allowed us to look at the power of orthographic and phonological cues to derive the tense of the verb. Two experiments showed that orthographic cues alone suffice to recover the tense of the verb, and that this recovery does not take more time than tense recovery on the basis of a combination of orthographic and phonological cues. On the basis of these results, we conclude that orthographic cues in homophones are very efficient during silent reading. Our findings, however, do not allow us to conclude whether this is due to a direct route from orthography to meaning, or to a specialised, morpho-syntactic back-up strategy elicited by certain sequences of letters.     

How does orthographic knowledge influence performance on phonological awareness tasks?

Three experiments explored the nature of orthographic influences on performance on phonological awareness tasks. Experiment 1 demonstrated that adults find it easier to perform phoneme deletions on items where there is a direct correspondence between letters and target sounds (e.g., take the /r@/ from struggle) than where there is not (e.g., take the /w@/ from squabble). Analogous results were found in a phoneme reversal task. Spelling production ability tended to correlate more strongly with performance on the former type of item than on the latter, suggesting that elevated performance on phonological awareness tasks is associated with the use of orthographic information. Experiment 2 produced similar results in Grade 5 children. Experiment 3 suggested that adults cannot inhibit orthographic activation when it is disadvantageous to them, as they performed no better on items such as squabble when they were presented in pure blocks than when they were presented in mixed blocks. It is concluded that there are substantial automatic orthographic influences on phonological awareness task performance that need to be taken into account in interpreting data concerning the relationship between phonological awareness and reading.     

Naming problems do not reflect a second independent core deficit in dyslexia: Double deficits explored

The double deficit hypothesis states that naming speed problems represent a second core deficit in dyslexia independent from a phonological deficit. The current study investigated the main assumptions of this hypothesis in a large sample of well-diagnosed dyslexics. The three main findings were that (a) naming speed was consistently related only to reading speed; (b) phonological processing speed and naming speed loaded on the same factor, and this factor contributed strongly to reading speed; and (c) although general processing speed was involved in speeded naming of visual items, it did not explain the relationship between naming speed and reading speed. The results do not provide support for the existence of a second independent core naming deficit in dyslexia and indicate that speeded naming tasks are mainly phonological processing speed tasks with an important addition: fast cross-modal matching of visual symbols and phonological codes.     

EVIDENCE FOR SUPERIOR ORTHOGRAPHIC SKILLS IN DYSLEXICS

Abstract— The purpose of this study was to assess the development of both phonological and orthographic skills in normally achieving and dyslexic readers The subjects were 257 dyslexic and 342 normally achieving readers, matched at eight reading levels They were administered the Woodcock (1987) Word Attack Subtest, a measure of phonological skills requiring the designed to measure awareness of the properties of English words and the probable sequences and positions of letters within words The dyslexics had significantly higher scores than the normally achieving readers on the orthographic awareness task However, the normally achieving readers had significantly higher scores on the Word Attack Subtest Therefore, the difficulties with phonological processing and the increased orthographic awareness of the dyslexics may indicate a reading strategy that relies more on the visual than the phonological.     

Training phonological awareness with and without explicit attention to articulation

One hundred twenty-two second- to fifth-grade (7- to 11-year-old) children with reading difficulties studied phonological awareness with or without explicit attention to articulation and with or without manipulation of sounds. They all studied identical phonics and read stories on the computer with speech and decoding support for difficult words. Regular-instruction controls received regularly scheduled language-arts or reading activities. After 40 h of training, children in all three trained conditions outperformed controls on all tests except math. Conditions that manipulated sounds showed advantages over the condition without explicit practice manipulating sounds, but only on the two measures of phonological awareness. Articulatory awareness training yielded no unique benefits during this training period. Individual differences in response to treatment related to initial levels of phonological awareness, naming speed, IQ, and grade. The similar outcomes of the three conditions suggest that specific variations in good phonological training may be less important than once thought for most children with reading difficulties.     

Simplifying reading: applying the simplicity principle to reading

Debates concerning the types of representations that aid reading acquisition have often been influenced by the relationship between measures of early phonological awareness (the ability to process speech sounds) and later reading ability. Here, a complementary approach is explored, analyzing how the functional utility of different representational units, such as whole words, bodies (letters representing the vowel and final consonants of a syllable), and graphemes (letters representing a phoneme) may change as the number of words that can be read gradually increases. Utility is measured by applying a Simplicity Principle to the problem of mapping from print to sound; that is, assuming that the "best" representational units for reading are those which allow the mapping from print to sounds to be encoded as efficiently as possible. Results indicate that when only a small number of words are read whole-word representations are most useful, whereas when many words can be read graphemic representations have the highest utility.     

Phonological codes are assembled before word fixation: evidence from boundary paradigm in sentence reading

This experiment employed the boundary paradigm during sentence reading to explore the nature of early phonological coding in reading. Fixation durations were shorter when the parafoveal preview was the correct word than when it was a spelling control pseudoword. In contrast, there was no significant difference between correct word and pseudohomophone previews. These results suggest that the phonological codes are assembled before word fixation and are used for lexical access. Moreover, there was evidence that orthographic codes influence the activation of word meaning. We found that fixation durations were shorter for orthographically similar parafoveal previews, and this orthographic priming effect is limited to pseudohomophones. Thus, it seems that both the orthographic and the phonological similarities of the parafoveal preview to the target play a part in the facilitative effects of the preview.     

"The W and M are mixing me up": use of a visual code in verbal short-term memory tasks

When normal participants are presented with written verbal short-term memory tasks (e.g., remembering a set of letters for immediate spoken recall) there is evidence to suggest that the information is re-coded into phonological form. This paper presents a single case study of MJK whose reading follows the pattern of phonological dyslexia. In short-term memory tasks MJK does not phonologically re-code written materials but, it is argued, uses a visual code. There are three main lines of evidence for this, (a) MJK tends to substitute visually similar items for one another, (b) her performance is better with visual than auditory stimuli, and (c) she is able to remember numbers (e.g., 8) better than written words (e.g., eight). Investigation of short-term memory in others with phonological dyslexia is warranted.     

The Foundations of Literacy

Learning to read and write in English requires children to master the alphabetic principle, the idea that the letters in printed words represent the sounds in spoken words in a more or less regular manner. Children need at least two skills in order to grasp the alphabetic principle. The first is phonological awareness, or a sensitivity to the sound structure of spoken words. The second is knowledge about letters, including knowledge of letter names and knowledge of letter sounds. Recent research sheds light on these foundational skills, documenting the linguistic factors that affect children's performance and how children put their phonological skills and knowledge of letters to use in learning to read and spell.