Teresa Schubert

Shared versus separate processes for letter and digit identification.

Letters and digits, although similar in many respects, also differ in potentially significant ways. Most importantly, letters are elements of an alphabetic writing system, whereas digits are logographs. In this article, we explore whether letters and digits are identified by a single character identification process that makes no fundamental distinction between the two types of characters, or whether instead letter and digit identification processes diverge at least in some respects. We present evidence from an acquired dyslexic patient, L.H.D., who is impaired in both letter and digit identification. Working within a theoretical framework specifying the levels of representation implicated in letter identification, we systematically compare L.H.D.s letter and digit processing. The results provide evidence that letter and digit identification implicate the same levels of representation, and further that L.H.D.s identification errors for both letters and digits arise at the same point in processing. On the basis of these results, we argue for a shared process that mediates identification of both letters and digits. Finally, we discuss relevant previous results in light of this conclusion.

Prelexical representations and processes in reading: Evidence from acquired dyslexia

We report a detailed and extensive single-case study of an acquired dyslexic patient, L.H.D., who suffered a left-hemisphere lesion as a result of a ruptured aneurysm. We present evidence that L.H.D.’s reading errors stem from a deficit in visual letter identification, and we use her deficit as a basis for exploring a variety of issues concerning prelexical representations and processes in reading. First, building on the work of other researchers, we present evidence that the prelexical reading system includes an allograph level of representation that represents each distinct visual shape of a letter (e.g., a, A, etc., for the letter A). We extend a theory proposed by Caramazza and Hillis [Caramazza, A., & Hillis, A. (1990a). Spatial representation of words in the brain implied by studies of a unilateral neglect patient. Nature, 346, 267–269] to include an allograph level, and we probe the nature of the allograph representations in some detail. Next, we explore the implications of visual similarity effects and letter perseverations in L.H.D.’s reading performance, arguing that these effects shed light on activation dynamics in the prelexical reading system and on the genesis of L.H.D.’s errors. We also probe the processing of letter case in the visual letter identification process, proposing that separate abstract letter identity and case representations are computed. Finally, we present evidence that the allograph level as well as the abstract letter identity level implement a word-based frame of reference.

Representation of letter position in single-word reading: Evidence from acquired dyslexia

Visual word recognition requires information about the positions as well as the identities of the letters in a word. This study addresses representation of letter position at prelexical levels of the word recognition process. We present evidence from an acquired dyslexic patient, L.H.D., who perseverates letters in single-word reading tasks: Far more often than expected by chance, L.H.D.s reading responses include letters from preceding responses (e.g., SAILOR read as SAILOG immediately after FLAG was read correctly). Analyses carried out over two large data sets compared the positions of perseverated letters (e.g., the G in SAILOG) with the positions of the corresponding “source” letters (e.g., the G in FLAG). The analyses assessed the extent to which the perseverations preserved source position as defined by various theories of letter position representation. The results provided strong evidence for graded both-edges position representations, in which the position of each letter is encoded coarsely relative to both the beginning and the end of the word. Alternative position representation schemes, including letter-context and orthosyllabic schemes, were not supported.

Why are digits easier to identify than letters

ABSTRACT Beginning with Dejerines report of pure alexia in 1892, numerous researchers have noted that individuals with acquired impairments of reading may show spared digit identification performance. This digit advantage has also been found in unimpaired adult readers across a number of tasks, and five main hypotheses have been proposed to explain how it arises. In this paper I consider these hypotheses in the context of recent theories of a unified alphanumeric character identification system, and evaluate them according to relevant empirical evidence. Despite some promising findings, none of the hypotheses currently provide a sufficient explanation of the digit advantage. Rather than developing new hypotheses to explain a categorical difference between digit and letter performance, I argue that future work should consider factors that affect identification performance specific to individual characters. HIGHLIGHTSAn advantage for digit identification is found in dyslexia and unimpaired reading.Previous hypotheses for the advantage are largely unable to explain the findings.The reported categorical digit advantage may mask inter‐character differences.Future work should examine why some digits are identified easier than some letters.

Recognition of oral spelling is diagnostic of the central reading processes

The task of recognition of oral spelling (stimulus: “C-A-T”, response: “cat”) is often administered to individuals with acquired written language disorders, yet there is no consensus about the underlying cognitive processes. We adjudicate between two existing hypotheses: Recognition of oral spelling uses central reading processes, or recognition of oral spelling uses central spelling processes in reverse. We tested the recognition of oral spelling and spelling to dictation abilities of a single individual with acquired dyslexia and dysgraphia. She was impaired relative to matched controls in spelling to dictation but unimpaired in recognition of oral spelling. Recognition of oral spelling for exception words (e.g., colonel) and pronounceable nonwords (e.g., larth) was intact. Our results were predicted by the hypothesis that recognition of oral spelling involves the central reading processes. We conclude that recognition of oral spelling is a useful tool for probing the integrity of the central reading processes.

Allograph priming is based on abstract letter identities: evidence from Japanese kana

It is well-established that allographs like the uppercase and lowercase forms of the Roman alphabet (e.g., a and A) map onto the same “abstract letter identity,” orthographic representations that are independent of the visual form. Consistent with this, in the allograph match task (“Are ‘a’ and ‘A’ the same letter?”), priming by a masked letter prime is equally robust for visually dissimilar prime-target pairs (e.g., d and D) and similar pairs (e.g., c and C). However, in principle this pattern of priming is also consistent with the possibility that allograph priming is purely phonological, based on the letter name. Because different allographic forms of the same letter, by definition, share a letter name, it is impossible to rule out this possibility a priori. In the present study, we investigated the influence of shared letter names by taking advantage of the fact that Japanese is written in two distinct writing systems, syllabic kana—that has two parallel forms, hiragana and katakana—and logographic kanji. Using the allograph match task, we tested whether a kanji prime with the same pronunciation as the target kana (e.g., special characters please refer to PDF, both pronounced /i/) produces the same amount of priming as a kana prime in the opposite kana form (e.g., special characters please refer to PDF). We found that the kana primes produced substantially greater priming than the phonologically identical kanji prime, which we take as evidence that allograph priming is based on abstract kana identity, not purely phonology.

Development of children’s identity and position processing for letter, digit, and symbol strings: A cross-sectional study of the primary school years

Letter recognition and digit recognition are critical skills for literate adults, yet few studies have considered the development of these skills in children. We conducted a nine-alternative forced-choice (9AFC) partial report task with strings of letters and digits, with typographical symbols (e.g.,

Evidence for cross-script abstract identities in learners of Japanese kana

, @) as a control, to investigate the development of identity and position processing in children. This task allows for the delineation of identity processing (as overall accuracy) and position coding (as the proportion of position errors). Our participants were students in Grade 1 to Grade 6, allowing us to track the development of these abilities across the primary school years. Our data suggest that although digit processing and letter processing end up with many similarities in adult readers, the developmental trajectories for identity and position processing for the two character types differ. Symbol processing showed little developmental change in terms of identity or position accuracy. We discuss the implications of our results for theories of identity and position coding: modified receptive field, multiple-route model, and lexical tuning. Despite moderate success for some theories, considerable theoretical work is required to explain the developmental trajectories of letter processing and digit processing, which might not be as closely tied in child readers as they are in adult readers.

Knowledge about writing influences reading: Dynamic visual information about letter production facilitates letter identification

The presence of abstract letter identity representations in the Roman alphabet has been well documented. These representations are invariant to letter case (upper vs. lower) and visual appearance. For example, “a” and “A” are represented by the same abstract identity. Recent research has begun to consider whether the processing of non-Roman orthographies also involves abstract orthographic representations. In the present study, we sought evidence for abstract identities in Japanese kana, which consist of two scripts, hiragana and katakana. Abstract identities would be invariant to the script used as well as to the degree of visual similarity. We adapted the cross-case masked-priming letter match task used in previous research on Roman letters, by presenting cross-script kana pairs and testing adult beginning -to- intermediate Japanese second-language (L2) learners (first-language English readers). We found robust cross-script priming effects, which were equal in magnitude for visually similar (e.g., り/リ) and dissimilar (e.g., あ/ア) kana pairs. This pattern was found despite participants’ imperfect explicit knowledge of the kana names, particularly for katakana. We also replicated prior findings from Roman abstract letter identities in the same participants. Ours is the first study reporting abstract kana identity priming (in adult L2 learners). Furthermore, these representations were acquired relatively early in our adult L2 learners.

Nonlinear spelling in graphemic buffer deficit

How are reading and writing related? In this study, we address the relationship between letter identification and letter production, uncovering a link in which production information can be used to identify letters presented dynamically. By testing an individual with a deficit in letter identification, we identified a benefit which would be masked by ceiling effects in unimpaired readers. In Experiment 1 we found that letter stimuli defined by the direction of dot motion (tiny dots within letter move leftward, background dots move rightward) provided no advantage over static letters. In Experiment 2, we tested dynamic stimuli in which the letter shapes emerged over time: drawn as they would be written, drawn in reverse, or with the letter shape filled in randomly. Improved identification was observed only for letters drawn as they are typically written. These results demonstrate that information about letter production can be integrated into letter identification, and point to bi-directional connections between stored letter production information (used for writing) and abstract letter identity representations (used in both reading and writing). The links from stored production information to abstract letter identities allow the former to activate the latter. We also consider the implications of our results for remediation of acquired letter identification deficits, including letter-drawing treatments and the underlying cause of their efficacy.