Phonological dyslexia: a test case for reading models

Following brain damage, skilled readers may encounter more severe problems in reading nonwords than familiar words, a type of deficit referred to as phonological dyslexia. We report on 2 individuals with Alzheimer's disease who show phonological dyslexia. Although highly accurate in reading familiar words aloud (even those with irregular spelling, such as sew), they were quite impaired in nonword reading. Both patients performed well in phonological tasks involving the repetition, identification, and manipulation of phonemes of orally presented words and nonwords. These results challenge the idea, proposed in the context of connectionist and evolutionary theories, that phonological dyslexia originates from a phonological deficit. However, the results are consistent with reading models, such as the dual-route model, that attribute phonological dyslexia to a deficit that selectively affects the reading mechanisms responsible for deriving the sounds of nonwords. According to these models, such a deficit is not necessarily accompanied by a more general phonological impairment.     

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.     

Lesion localization of phonological agraphia.

Phonological agraphia is a neurolinguistically specific profile of spelling impairment. It is characterized by an impairment in spelling pronounceable pseudowords ('sild') and by an impairment in spelling real words related to their familiarity, length, and often, part of speech (Shallice, 1981; Roeltgen, 1985; Bub & Chertkow, 1988). We report two cases of phonological agraphia, each with a different lesion profile. Analysis of the small number of published cases that include lesion data, plus our own cases, suggests that phonological agraphia can be produced by lesions in a wide range of perisylvian cortical regions that have in common some role in central phonological processes.     

Is a "Phoenician" reading style superior to a "Chinese" reading style? Evidence from fourth graders

This study compared normally achieving fourth-grade "Phoenician" readers, who identify nonwords significantly more accurately than they do exception words, with "Chinese" readers, who show the reverse pattern. Phoenician readers scored lower than Chinese readers on word identification, exception word reading, orthographic choice, spelling, reading comprehension, and verbal ability. When compared with normally achieving children who read nonwords and exception words equally well, Chinese readers scored as well as these children on word identification, regular word reading, orthographic choice, spelling, reading comprehension, phonological sensitivity, and verbal ability and scored better on exception word reading. Chinese readers also used rhyme-based analogies to read nonwords derived from high-frequency exception words just as often as did these children. As predicted, Phoenician and Chinese readers adopted somewhat different strategies in reading ambiguous nonwords constructed by analogy to high-frequency exception words. Phoenician readers were more likely than Chinese readers to read ambiguous monosyllabic nonwords via context-free grapheme-phoneme correspondences and were less likely to read disyllabic nonwords by analogy to high-frequency analogues. Although the Chinese reading style was more common than the Phoenician style in normally achieving fourth graders, there were similar numbers of poor readers with phonological dyslexia (identifying nonwords significantly more accurately than exception words) and surface dyslexia (showing the reverse pattern), although surface dyslexia was more common in the severely disabled readers. However, few of the poor readers showed pure patterns of phonological or surface dyslexia.     

Lexical access for low- and high-frequency words in Hebrew

The hypothesis that phonological mediation is involved to a greater extent in the recognition of low- than in the recognition of high-frequency words was examined using Hebrew. Hebrew has two forms of spelling, pointed and unpointed, which differ greatly in the extent of phonological ambiguity, with the unpointed spelling lacking almost all vowel information. A lexical decision task was employed using target words that had only one pronunciation whether pointed or unpointed. Targets were either pointed or unpointed and were preceded by a prime, which for word targets, was either semantically related or unrelated. The results indicated the following: First, the advantage of pointed over unpointed spelling was larger for low-frequency than for high-frequency words, suggesting a stronger phonological mediation for low-frequency words. Second, the size of the pointing effect was independent of word length, suggesting that phonology is obtained on the basis of the printed word as a whole, by looking it up in a phonological lexicon. Third, response latency to nonwords was not affected by the presence or absence of pointing, suggesting that failure to locate the entry corresponding to a letter string in a phonological lexicon results in a NO decision. Fourth, presence of a related prime was not found to compensate for absence of pointing, suggesting that the activation of a word’s representation in the semantic lexicon does not aid access to its corresponding entry in the phonological lexicon.     

Reading with partial phonology: Developmental phonological dyslexia

Recent psycholinguistic investigations have advanced our understanding of the acquired dyslexias. Developmental analogues have been described to some of these disorders. A new case of developmental phonological dyslexia is described here. A.H. is an intelligent 10-year-old boy with no neurological abnormality. Reading and spelling are below age level. A.H. is poorer at reading words than nonwords. The majority of his errors are paralexias: visual, derivations, or visuosemantic. Spelling-to-sound regularity does not affect the ability to read aloud. A.H.'s reading performance is significantly impaired when words are presented typed in reverse order, thereby prohibiting global strategies. Spelling of nonwords is no better than reading of nonwords. Only one-fifth of spelling errors are phonologically valid. A.H. has imperfect development of both the phonological route to reading and the phonological route to spelling.A shortened version of this paper was presented at the European meeting of the International Neuropsychological Society, Lisbon, Portugal, June 1983.     

The processing of pseudohomophones by adults with a history of developmental language disabilities

Psuedohomophones are nonwords that sound like real words (e.g., BRANE). These items were used to gauge phonological access in adults who have experienced developmental language processing deficits (DLD). The standard effect for these items in lexical decision is an increase in response times over nonpseudohomophone nonwords. This disadvantage reflects phonological processing. In our first experiment the DLD group did not produce this pseudohomophone effect whereas in a second experiment they showed semantic priming effects when pseudohomophones were used as primes in lexical decision. The results therefore indicate that phonological processing of nonwords by adults with DLD can be uncovered under certain carefully controlled experimental conditions.     

Reading: dissociation of the lexical and phonologic mechanisms

Three distinct reading mechanisms have been proposed: the phonologic conversion system in which letters are converted to their sound equivalents (phonemes) before meaning is established, and two lexical or whole-word mechanisms in which a word (or root morpheme) is identified as a single unit rather than by phonologic conversion. The two lexical mechanisms differ in that one is inextricably linked to semantics but the other is not. The phonologic conversion system may depend more on the perisylvian phonologic system than do the lexical mechanisms, which may be mediated by left parietal or occipital areas or by the right hemisphere. Described here is a patient who had an infarction that partially isolated the perisylvian speech areas and disconnected the partially preserved lexical systems from the phonologic mechanism. He read visually presented orthographically irregular words but could not pronounce orally spelled irregular words. Although he could not read nonwords, he could pronounce orally spelled nonwords and orthographically regular words. These observations suggest that the lexical and phonologic conversion systems are functionally and anatomically distinct.     

What exactly is a yait anyway: The role of semantics in orthographic learning

This study investigated whether semantic information presented along with novel printed nonwords facilitates orthographic learning and examined predictors of individual differences in this important literacy skill. A sample of 35 fourth graders was tested on a variety of language and literacy tests, and participants were then exposed to 10 target nonwords, 5 of which were presented with semantic information. Children were tested 1 and 4 days later on their ability to correctly recognize and spell the target nonwords. Results revealed a significant main effect on the recognition task, where items presented with semantic information were identified correctly more often than were words presented in isolation. No significant effect of training condition was found for the spelling posttests. Furthermore, multiple regression analyses revealed that both phonological and semantic factors were significant predictors of orthographic learning. The findings support the view that orthographic learning, as measured through visual recognition, involves the integration of phonological, orthographic, and semantic representations.     

Spelling in Adults: The Combined Influences of Language Skills and Reading Experience

One hundred and twelve university students completed 7 tests assessing word-reading accuracy, print exposure, phonological sensitivity, phonological coding and knowledge of English morphology as predictors of spelling accuracy. Together the tests accounted for 71% of the variance in spelling, with phonological skills and morphological knowledge emerging as strong predictors of spelling accuracy for words with both regular and irregular sound-spelling correspondences. The pattern of relationships was consistent with a model in which, as a function of the learning opportunities that are provided by reading experience, phonological skills promote the learning of individual word orthographies and structural relationships among words.     

Oral reading in dementia

Reading has been thought to consist of three main processing components: the orthographic, phonological, and semantic lexicons. In traditional psycholinguistic models, these components have been treated independently such that the selective dysfunction of one does not necessarily imply the breakdown of another. Recently, it has been proposed that a word's semantic representation is essential to oral reading such that a disturbance within the semantic lexicon will disrupt processing within the orthographic and/or phonological lexicons. From this view, semantic deterioration should lead to fragmentation of the other systems contributing to reading, resulting in a specific pattern of errors during oral reading. This would include (1) a larger than normal advantage for reading words with regular spelling-to-sound correspondence over words with exception spelling, as well as the production of "regularization errors" when reading exception words; and (2) a smaller than normal difference between reading real words and pronounceable nonwords, or pseudowords (PW's). We found that patients with Semantic Dementia generally conformed to these hypothesized patterns of reading difficulty. Despite the presence of a semantic impairment, however, patients with Alzheimer's Disease, Frontotemporal Dementia, and Progressive Non-Fluent Aphasia did not demonstrate these patterns of reading difficulty. Our findings suggest that not all semantic impairments invariably lead to the disruption of the orthographic and phonological lexicons.     

The role of linguistic and visual information in spelling: a developmental study

This study investigated the processes that elementary school children use for spelling. Good and poor spellers in grades 3 through 6 spelled words and nonwords that differed in the types of information (phonological, orthographic, morphological, or visual) that could be used to produce their correct spelling. A multiple choice spelling recognition task was also administered. Error rates on words and nonwords were related to the type of information that could be used to determine the correct spelling. Words that could be spelled on the basis of linguistic information were easier than words that could be spelled only on the basis of visual information. While children were sensitive to the linguistic properties of the stimuli, their use and knowledge of various sources of linguistic information was not uniformly developed. Children had the most difficulty with spellings based on morphological information and the least difficulty with those based on invariant sound-spelling relationships. On the dictation and the nonword tasks, younger children and poorer spellers differed from older children and better spellers in the overall level of their knowledge, but all children showed a similar pattern of results suggesting that they did not use different processes to spell words. However, the data from the recognition task suggested that poor spellers may rely more on visual information than good spellers.     

Modulation of brain activity during phonological familiarization

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri. At the same time, interaction analysis showed that the magnitude of decrease of activity in bilateral posterior temporal lobe was significantly smaller for LF nonwords, relative to words and HF nonwords. Decrease of activity in this area also correlated with the size of behavioral familiarization effects for LF nonwords. The results show that the posterior superior temporal gyrus plays a fundamental role during phonological learning. Its relationship to sublexical and lexical phonological processing as well as to phonological short-term memory is discussed.     

Right-hemisphere reading in a case of developmental deep dyslexia

The right-hemisphere hypothesis of deep dyslexia has received support from functional imaging studies of acquired deep dyslexia following damage to the left cerebral hemisphere, but no imaging studies of cases of developmental deep dyslexia, in which brain damage is not suspected, have been reported. In this paper, we report the first evidence of right hyperactivation in an adult case of developmental deep dyslexia. Hyperactivation was observed in the right inferior frontal cortex during functional magnetic resonance imaging (fMRI) of the oral reading of imageable content words and nonwords to which imageable lexical responses were frequently made. No evidence of right hyperactivation was observed in the oral reading of function words, nor during the naming of imageable words in response to pictured objects. The results reveal strategic and selective use of right-hemisphere functions for particular types of written stimuli. We propose that children with developmental deep dyslexia compensate for their lack of phonological skills by accessing right-hemisphere imageable associations that provide a mnemonic for linking written forms to spoken names.     

Right-hemisphere reading in a case of developmental deep dyslexia

The right-hemisphere hypothesis of deep dyslexia has received support from functional imaging studies of acquired deep dyslexia following damage to the left cerebral hemisphere, but no imaging studies of cases of developmental deep dyslexia, in which brain damage is not suspected, have been reported. In this paper, we report the first evidence of right hyperactivation in an adult case of developmental deep dyslexia. Hyperactivation was observed in the right inferior frontal cortex during functional magnetic resonance imaging (fMRI) of the oral reading of imageable content words and nonwords to which imageable lexical responses were frequently made. No evidence of right hyperactivation was observed in the oral reading of function words, nor during the naming of imageable words in response to pictured objects. The results reveal strategic and selective use of right-hemisphere functions for particular types of written stimuli. We propose that children with developmental deep dyslexia compensate for their lack of phonological skills by accessing right-hemisphere imageable associations that provide a mnemonic for linking written forms to spoken names.     

Left hemisphere superiority for pronounceable nonwords,but not for unpronounceable letter strings

Right-handed adults were asked to identify bilaterally presented linguistic stimuli under three experimental conditions. In Condition A, stimuli were three-letter pronounceable nonwords (such as TUP), and subjects were asked to report them by naming them. In Condition B, stimuli were three-letter pronounceable nonwords, and subjects were asked to report them as strings of letters. In Condition C, stimuli were more or less unpronounceable letter strings (such as UTP) created by rearranging the letters of pronounceable nonwords, and subjects reported them as strings of letters. Pronounceable nonwords were found to be better identified from the right visual hemifield irrespective of the way in which they were reported. Unpronounceable letter strings did not produce any visual hemifield difference. Nonwords are of interest because they can be seen as potential words that lack both specific semantic properties and entries in the subject's internal lexicon. The results of the experiment are consistent with the view that both the left and right cerebral hemispheres are able to identify letters but the left hemisphere is more sensitive to the pronounceability of the nonwords. This may happen either because the left hemisphere can make better use of resemblances to real words or because it has access to spelling to sound correspondence rules.     

Attentional strategic control over nonlexical and lexical processing in written spelling to dictation in adults

We conducted four experiments to investigate whether adults can exert attentional strategic control over nonlexical and lexical processing in written spelling to dictation. In Experiment 1, regular and irregular words were produced either in a nonword context (regular and irregular nonwords) or in a word context (high-frequency regular and irregular words), whereas in Experiment 2, the same set of words was produced either in a regular nonword or in an irregular low-frequency word context. Experiment 3 was a replication of Experiment 2 but with increased manipulation of the context. In Experiment 4, participants had to produce either under time pressure or in response to standard written spelling instructions. Regularity effects were found in all the experiments, but their size was not reliably affected by manipulations intended to increase or decrease reliance on nonlexical processing. More particularly, the results from Experiment 4 show that adults can speed up the initialization of their writing responses to a substantial degree without altering regularity effects on either latencies or spelling errors. Our findings suggest that, although adults are able to generate an internal deadline criterion of when to initialize the writing responses, nonlexical processing is a mandatory process that is not subject to attentional strategic control in written spelling to dictation.     

Deaf and hearing children's plural noun spelling

The present study examines deaf and hearing children's spelling of plural nouns. Severe literacy impairments are well documented in the deaf, which are believed to be a consequence of phonological awareness limitations. Fifty deaf (mean chronological age 13;10 years, mean reading age 7;5 years) and 50 reading-age-matched hearing children produced spellings of regular, semiregular, and irregular plural nouns in Experiment 1 and nonword plurals in Experiment 2. Deaf children performed reading-age appropriately on rule-based (regular and semiregular) plurals but were significantly less accurate at spelling irregular plurals. Spelling of plural nonwords and spelling error analyses revealed clear evidence for use of morphology. Deaf children used morphological generalization to a greater degree than their reading-age-matched hearing counterparts. Also, hearing children combined use of phonology and morphology to guide spelling, whereas deaf children appeared to use morphology without phonological mediation. Therefore, use of morphology in spelling can be independent of phonology and is available to the deaf despite limited experience with spoken language. Indeed, deaf children appear to be learning about morphology from the orthography. Education on more complex morphological generalization and exceptions may be highly beneficial not only for the deaf but also for other populations with phonological awareness limitations.     

Developmental dysgraphias

Two cases of developmental dysgraphia are presented. These ten-year-old children are of at least average intelligence and vocabulary, with normal speech and no known neurological abnormality. Psycholinguistic investigations reveal that although performance for the two cases is quantitatively similar, there are marked qualitative differences: The majority of R.B.'s spelling errors are phonologically plausible, and she is better at spelling regular than irregular words. Non-word spelling is as good as word spelling. The pattern of spelling deficit is consistent with the label surface dysgraphia. A phonological route to spelling has developed in relative isolation from a lexical-semantic route to spelling. A.H.'s spelling contrasts in a number of ways with R.B.'s. Fewer than 1/5 of his spelling errors are phonologically plausible, and the spelling of regular words is no better than the spelling of irregular words. A.H. may have impaired development of the segmentation component of the phonological route and therefore be overreliant on an, albeit imperfect, lexical-semantic spelling route. Normal children at the same spelling level display patterns of performance similar to R.B. but differ quantitatively from A.H.     

When children write nonwords to dictation

Skill in written spelling of simple, monosyllabic nonwords was investigated in 9- to 11-year-old English children. Two aspects of their spellings were of interest: first, could they spell these nonwords so that they sounded correct (nonword spelling accuracy), and second, did their spellings show evidence of biasing from words heard earlier in the test sequence? Nonword spelling was poorer for children of this age than for tested adults. Nevertheless, significant biasing occurred in these children's spellings, though not to the same extent as in adults' nonword spellings, and significant correlations emerged between reading age, nonword spelling skill, susceptibility to biasing, and real word spelling skill. Children with a reading age greater than 11 years showed biasing from word spellings that was within range of that reported for adults, and, for these more skilled readers, word spelling accuracy correlated significantly with both susceptibility to biasing and with nonword spelling accuracy. These children were not as accurate as tested adults at spelling nonwords. Children with a reading age below 11 years were poorer at nonword spelling and showed no overall biasing, yet they also showed a significant correlation between word spelling skill and nonword biasing. Together with evidence from the same task from adults with specific spelling disorders, these results suggest that word knowledge had a direct (biasing) and an indirect (general word spelling knowledge) effect on the performance of the nonword spelling task. But although skill in word spelling may be a necessary prerequisite for nonword spelling, it need not always be sufficient.