Towards a universal model of reading

Functional neuroanatomy of developmental dyslexia: the role of orthographic depth

Orthographic depth (OD) (i.e., the complexity, consistency, or transparency of grapheme-phoneme correspondences in written alphabetic language) plays an important role in the acquisition of reading skills. Correspondingly, developmental dyslexia is characterized by different behavioral manifestations across languages varying in OD. This review focuses on the question of whether these different behavioral manifestations are associated with different functional neuroanatomical manifestations. It provides a review and critique of cross-linguistic brain imaging studies of developmental dyslexia. In addition, it includes an analysis of state-of-the-art functional neuroanatomical models of developmental dyslexia together with orthography-specific predictions derived from these models. These predictions should be tested in future brain imaging studies of typical and atypical reading in order to refine the current neurobiological understanding of developmental dyslexia, especially with respect to orthography-specific and universal aspects.

Orthographic Coding in Illiterates and Literates

We investigated how literacy modifies one of the mechanisms of the visual system that is essential for efficient reading: flexible position coding. To do so, we focused on the abilities of literates and illiterates to compare two-dimensional strings of letters (Experiment 1) and symbols (Experiment 2) in which the positions of characters had been manipulated. Results from two perceptual matching experiments revealed that literates were sensitive to alterations in characters’ within-string position and identity, whereas illiterates are almost blind to these changes. We concluded that letter-position coding is a mechanism that emerges during literacy acquisition and that the recognition of sequences of objects is highly modulated by reading skills. These data offer new insights about the manner in which reading acquisition shapes the visual system by making it highly sensitive to the internal structure of sequences of characters.

Real-time Functional Architecture of Visual Word Recognition

Despite a century of research into visual word recognition, basic questions remain unresolved about the functional architecture of the process that maps visual inputs from orthographic analysis onto lexical form and meaning and about the units of analysis in terms of which these processes are conducted. Here we use magnetoencephalography, supported by a masked priming behavioral study, to address these questions using contrasting sets of simple (walk), complex (swimmer), and pseudo-complex (corner) forms. Early analyses of orthographic structure, detectable in bilateral posterior temporal regions within a 150–230 msec time frame, are shown to segment the visual input into linguistic substrings (words and morphemes) that trigger lexical access in left middle temporal locations from 300 msec. These are primarily feedforward processes and are not initially constrained by lexical-level variables. Lexical constraints become significant from 390 msec, in both simple and complex words, with increased processing of pseudowords and pseudo-complex forms. These results, consistent with morpho-orthographic models based on masked priming data, map out the real-time functional architecture of visual word recognition, establishing basic feedforward processing relationships between orthographic form, morphological structure, and lexical meaning.

Does tonal information affect the early stages of visual-word processing in Thai?

Thai offers a unique opportunity to investigate the role of lexical tone processing during visual-word recognition, as tone is explicitly expressed in its script. In order to investigate the contribution of tone at the orthographic/phonological level during the early stages of word processing in Thai, we conducted a masked priming experiment-using both lexical decision and word naming tasks. For a given target word (e.g., ห้อง/hᴐ:ŋ2/, room), five priming conditions were created: (a) identity (e.g., ห้อง/hᴐ:ŋ2/), (b) same initial consonant, but with a different tone marker (e.g., ห่อง/hᴐ:ŋ1/), (c) different initial consonant, but with the same tone marker (e.g., ศ้อง/sᴐ:ŋ2/), (d) orthographic control (different initial consonant, different tone marker; e.g., ศ่อง/sᴐ:ŋ1/), and (e) same tone homophony, but with a different initial consonant and different tone marker (e.g., ธ่อง/t(h)ᴐ:ŋ2/). Results of the critical comparisons revealed that segmental information (i.e., consonantal information) appears to be more important than tone information (i.e., tone marker) in the early stages of visual-word processing in alphabetic, tonal languages like Thai. Thus, these findings may help constrain models of visual-word recognition and reading in tonal languages.

Neural division of labor in reading is constrained by culture: a training study of reading Chinese characters

Word reading in alphabetic language involves a cortical system with multiple components whose division of labor depends on the transparency of the writing system. To gain insight about the neural division of labor between phonology and semantics subserving word reading in Chinese, a deep non-alphabetic writing system, functional magnetic resonance imaging (fMRI) was used to investigate the effects of phonological and semantic training on the cortical circuitry for oral naming of Chinese characters. In a training study, we examined whether a training task that differentially focused readers' attention on the phonological or semantic properties of a Chinese character changes the patterns of cortical activation that was evoked by that character in a subsequent naming task. Our imaging results corroborate that the cortical regions underlying reading in Chinese largely overlap the left-hemisphere reading system responsible for reading in alphabetic languages, with some cortical regions in the left-hemisphere uniquely recruited for reading in Chinese. However, in contrast to findings from studies of English word naming, we observed considerable overlap in the neural activation patterns associated with phonological and semantic training on naming Chinese characters, which we suggest may reflect a balanced neural division of labor between phonology and semantics in Chinese character reading. The equitable division of labor for Chinese reading might be driven by the special statistical structure of the writing system, which includes equally systematic mappings in the correspondences between written forms and their pronunciations and meanings.

Diagnostic profiles of children with developmental dyslexia in a transparent orthography

In the present study for 108 typical and 122 atypical Dutch readers in second grade, the accuracy and speed of decoding words and pseudowords, as well as the accuracy of spelling words were assessed along with four types of phonological precursor measures: rapid naming, verbal working memory, phoneme awareness and letter knowledge. The data show that the group being diagnosed as poor readers were significantly behind in all reading and spelling measures. It was also found that the criterion measures of reading and spelling explained already two third of the variance associated with the group distinction. Finally, we found word and pseudoword efficiency in the typical group to be explained by phonological awareness (spoonerism) and rapid naming of letters, word and pseudoword accuracy by phonological awareness, and spelling by phonological awareness and letter dictation. In the group of poor readers, a much greater variety of precursor measures was involved in explaining the variance in reading and spelling abilities.

Orthographic learning and self-teaching in a bilingual and biliterate context

The aim of this study was to examine self-teaching in the context of English as a foreign language literacy acquisition. Three groups comprising 88 sixth-grade children participated. The first group consisted of Russian-Hebrew-speaking bilinguals who had acquired basic reading skills in Russian as their first language (L1) and literacy and who were literate in Hebrew as a second language. The second group consisted of Russian-Hebrew-speaking bilinguals who had not learned to read in their native Russian but had acquired Hebrew as their first literate language. The third group consisted of Hebrew-speaking monolingual children who were literate in Hebrew. This design facilitated examining the effect of biliteracy and bilingualism on basic English reading skills. We hypothesized that due to the proximity between the Russian and English orthographies as opposed to the Hebrew-English "distance," the Russian-Hebrew-speaking biliterate group who acquired basic reading and spelling skills in L1 Russian would have superior self-teaching in English as opposed to the two other groups. The standard two-session self-teaching paradigm was employed with naming (speed and accuracy) and orthographic choice as posttest measures of orthographic learning. Results showed that after 4 years of English instruction, all three groups showed evidence of self-teaching on naming speed and orthographic recognition. The Russian-Hebrew-speaking biliterate group, moreover, showed a partial advantage over the comparison groups for initial decoding of target pseudowords and clear-cut superiority for measures of later orthographic learning, thereby showing self-teaching while supporting the script dependence hypothesis.

What predicts successful literacy acquisition in a second language?

In the study reported here, we examined whether success (or failure) in assimilating the structure of a second language can be predicted by general statistical-learning abilities that are nonlinguistic in nature. We employed a visual-statistical-learning (VSL) task, monitoring our participants' implicit learning of the transitional probabilities of visual shapes. A pretest revealed that performance in the VSL task was not correlated with abilities related to a general g factor or working memory. We found that, on average, native speakers of English who more accurately picked up the implicit statistical structure embedded in the continuous stream of shapes better assimilated the Semitic structure of Hebrew words. Languages and their writing systems are characterized by idiosyncratic correlations of form and meaning, and our findings suggest that these correlations are picked up in the process of literacy acquisition, as they are picked up in any other type of learning, for the purpose of making sense of the environment.

Early access to abstract representations in developing readers: evidence from masked priming

A commonly shared assumption in the field of visual-word recognition is that retinotopic representations are rapidly converted into abstract representations. Here we examine the role of visual form vs. abstract representations during the early stages of word processing - as measured by masked priming - in young children (3rd and 6th Graders) and adult readers. To maximize the chances of detecting an effect of visual form, we employed a language with a very intricate orthography, Arabic. If visual form plays a role in the early stages of processing, greater benefit would be expected from related primes that have the same visual form (in terms of the ligation pattern between a word's letters) as the target word (e.g.- [ktz b-ktA b] - note that the three initial letters are connected in prime and target) than for those that do not (- [ktxb-ktA b]). Results showed that the magnitude of priming effect relative to an unrelated condition (e.g. -) was remarkably similar for both types of prime. Thus, despite the visual complexity of Arabic orthography, there is fast access to the abstract letter representations not only in adult readers by also in developing readers.

Position coding effects in a 2D scenario: the case of musical notation

How does the cognitive system encode the location of objects in a visual scene? In the past decade, this question has attracted much attention in the field of visual-word recognition (e.g., "jugde" is perceptually very close to "judge"). Letter transposition effects have been explained in terms of perceptual uncertainty or shared "open bigrams". In the present study, we focus on note position coding in music reading (i.e., a 2D scenario). The usual way to display music is the staff (i.e., a set of 5 horizontal lines and their resultant 4 spaces). When reading musical notation, it is critical to identify not only each note (temporal duration), but also its pitch (y-axis) and its temporal sequence (x-axis). To examine note position coding, we employed a same-different task in which two briefly and consecutively presented staves contained four notes. The experiment was conducted with experts (musicians) and non-experts (non-musicians). For the "different" trials, the critical conditions involved staves in which two internal notes that were switched vertically, horizontally, or fully transposed--as well as the appropriate control conditions. Results revealed that note position coding was only approximate at the early stages of processing and that this encoding process was modulated by expertise. We examine the implications of these findings for models of object position encoding.

Letter transpositions within morphemes and across morpheme boundaries

Recent evidence has revealed conflicting results regarding the influence of letter transpositions during the recognition of morphologically complex words. While some studies suggest that the disruption of the morpheme boundary through across-boundary transpositions (e.g., darnkess) leads to the absence of masked transposed-letter (TL) priming, other studies have found that TL priming occurs independently of whether or not letters have been transposed across the boundary. We conducted three experiments to test whether the difference between TL- within and TL-across priming is modulated by (a) the transposition of internal versus external letters of the stem (Experiment 1), (b) the overall proportion of affixed trials (Experiment 2), or (c) the relative frequency between prime and target (Experiment 3). The results revealed equal TL-within and TL-across boundary priming across all three experiments, which adds to previous findings suggesting that across-boundary transpositions do not interfere with the recognition of morphologically complex words.

ERP correlates of letter identity and letter position are modulated by lexical frequency

The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (experiment 1) and lexical decision (experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition.

Orthographic influences on division of labor in learning to read Chinese and English: Insights from computational modeling

Learning to read any language requires learning to map among print, sound and meaning. Writing systems differ in a number of factors that influence both the ease and rate with which reading skill can be acquired, as well as the eventual division of labor between phonological and semantic processes. Further, developmental reading disability manifests differently across writing systems, and may be related to different deficits in constitutive processes. Here we simulate some aspects of reading acquisition in Chinese and English using the same model architecture for both writing systems. The contribution of semantic and phonological processing to literacy acquisition in the two languages is simulated, including specific effects of phonological and semantic deficits. Further, we demonstrate that similar patterns of performance are observed when the same model is trained on both Chinese and English as an "early bilingual." The results are consistent with the view that reading skill is acquired by the application of statistical learning rules to mappings among print, sound and meaning, and that differences in the typical and disordered acquisition of reading skill between writing systems are driven by differences in the statistical patterns of the writing systems themselves, rather than differences in cognitive architecture of the learner.

Are all Semitic languages immune to letter transpositions? The case of Maltese

Recent research using the rapid serial visual presentation (RSVP) paradigm with English sentences that included words with letter transpositions (e.g., jugde) has shown that participants can readily reproduce the correctly spelled sentences with little cost; in contrast, there is a dramatic reading cost with root-derived Hebrew words (Velan & Frost, Psychonomic Bulletin & Review 14:913-918, 2007, Cognition 118:141-156, 2011). This divergence could be due to (1) the processing of root-derived words in Semitic languages or (2) the peculiarities of the transitional probabilities in root-derived Hebrew words. Unlike Hebrew, Maltese is a Semitic language that does not omit vowel information in print and whose morphology also has a significant non-Semitic (mostly Romance) morphology. Here, we employed the same RSVP technique used by Velan and Frost (Psychonomic Bulletin & Review 14:913-918, 2007, Cognition 118:141-156, 2011), this time with Maltese (and English) sentences. The results showed that Maltese-English bilinguals were able to reproduce the Maltese words-regardless of whether they were misspelled (involving the transposition of two letters from the consonantal root) or not, with no reading cost-just as in English. The apparent divergences between the RSVP data with Hebrew versus Maltese sentences are likely due to the combination of the characteristics of the Hebrew orthographic system with the Semitic morphology.

Letter position coding across modalities: the case of Braille readers

Background

The question of how the brain encodes letter position in written words has attracted increasing attention in recent years. A number of models have recently been proposed to accommodate the fact that transposed-letter stimuli like jugde or caniso are perceptually very close to their base words.

Methodology

Here we examined how letter position coding is attained in the tactile modality via Braille reading. The idea is that Braille word recognition may provide more serial processing than the visual modality, and this may produce differences in the input coding schemes employed to encode letters in written words. To that end, we conducted a lexical decision experiment with adult Braille readers in which the pseudowords were created by transposing/replacing two letters.

Principal Findings

We found a word-frequency effect for words. In addition, unlike parallel experiments in the visual modality, we failed to find any clear signs of transposed-letter confusability effects. This dissociation highlights the differences between modalities.

Conclusions

The present data argue against models of letter position coding that assume that transposed-letter effects (in the visual modality) occur at a relatively late, abstract locus.

Parafoveal semantic information extraction in traditional Chinese reading

Semantic information extraction from the parafovea has been reported only in simplified Chinese for a special subset of characters and its generalizability has been questioned. This study uses traditional Chinese, which differs from simplified Chinese in visual complexity and in mapping semantic forms, to demonstrate access to parafoveal semantic information during reading of this script. Preview duration modulates various types (identical, phonological, and unrelated) of parafoveal information extraction. Parafoveal semantic extraction is more elusive in English; therefore, we conclude that such effects in Chinese are presumably caused by substantial cross-language differences from alphabetic scripts. The property of Chinese characters carrying rich lexical information in a small region provides the possibility of semantic extraction in the parafovea.

The role of visual acuity and segmentation cues in compound word identification

Studies are reviewed that demonstrate how the identification of compound words during reading is constrained by the foveal area of the eye. When compound words are short, their letters can be identified during a single fixation, leading to the whole-word route dominating word recognition from early on. Hence, marking morpheme boundaries visually by means of hyphens slows down the processing of short words by encouraging morphological decomposition when holistic processing is a feasible option. In contrast, the decomposition route dominates the early stages of identifying long compound words. Thus, visual marking of morpheme boundaries facilitates processing of long compound words, unless the initial fixation made on the word lands very close to the morpheme boundary. The reviewed pattern of results is explained by the visual acuity principle (Bertram and Hyönä, 2003) and the dual-route framework of morphological processing.