Letter Confusability Research Articles

Parafoveal letter identification in Russian: Confusion matrices based on error rates.

In the present study, we introduce parafoveal letter confusion matrices for the Russian language, which uses the Cyrillic script. To ensure that our confusion rates reflect parafoveal processing and no other effects, we employed an adapted boundary paradigm (Rayner, 1975) that prevented the participants from directly fixating the letter stimuli. Additionally, we assessed confusability under isolated and word-like (crowded) conditions using two modern fonts, since previous research showed that letter recognition depended on crowding and font (Coates, 2015; Pelli et al., 2006). Our additional goal was to gain insight into what letter features or configurational patterns might be essential for letter recognition in Russian; thus, we conducted exploratory clustering analysis on visual confusion scores to identify groups of similar letters. To support this analysis, we conducted a comprehensive review of over 20 studies that proposed crucial properties of Latin letters relevant to character perception. The summary of this review is valuable not only for our current study but also for future research in the field.

Difficulty of Visual Recognition: Identifying the Direction Confusion of Reading Letters in Young Children

Difficulty of Visual Recognition: Identifying the Direction Confusion of Reading Letters in Young Children

Effect of Colour Usage and Dialogue Reading Practices in Solving the Visual and Auditory Perception Problems of Students with Dyslexia

Dyslexia is a specific learning disability in reading. It is the most prevalent learning disability. This study aims to reveal the effect of the use of colours, peer assessment and reading dialogues on the education of students with dyslexia. The study uses a technical collaborative action research method. Two male students diagnosed with dyslexia and studying in the second year of primary school were participants in the study. The study lasted for 12 weeks following the research plan. The students were required to read the chosen tales in Aesop’s Tales aloud. After reading the stories, the students also read selected dialogues in the elementary school course books determined by the Ministry of National Education. Two letters by which the students got confused were marked in two different colours in the first text. The colouring gradually reduced in the new text. There was no colouring in the last text. Results show that the use of colours was effective in reducing the confusion of letters. The students corrected their mistakes mutually through the peer assessment method. The students liked the reading activity and made fewer reading errors compared to other texts.

Ocorrência dos processos cognitivos de leitura e escrita e habilidades perceptovisuais em escolares com Dislexia Visual

to evaluate and classify visual dyslexic students, considering that developmental dyslexia subtypes are not differentiated in most diagnoses and that they affect a generalized approach. Cross-sectional, observational, analytical study composed of 80 students, divided into two groups, GA (dyslexics) and GB (without complaints of learning difficulties) using PROLEC (proof of assessment of reading processes), TVPS - 3 (Visual Test of Perceptual Skills) and TPMBO (Bruininks-Oseretsky Motor Proficiency Test) - subtests 7 and 8. Comparing the groups, the students of GA presented inferior performance in all the PROLEC tests and in the TVPS3 tests. The TPMBO tests of visuomotor coordination and manual dexterity tests were inferior. In a second stage, screening the visual dyslexics, 12 (30%) schoolchildren were found, who presented better performance in reading frequent words, when compared to the performance in reading infrequent words and pseudowords. In the visual perceptual skills (TVPS-3), they obtained values below 50%, except for the subscale constancy of form. The occurrences of exchanges in reading aloud were in confusion of letters, syllables or words with little difference in the way of writing, but different in the direction, the same students did not present exchanges or confusions between letters, which have the same point and manner of articulation, and whose sounds are acoustically close. Thus, characterizing the dyslexia subtype is fundamental, because the application of therapeutic techniques will depend on the correct focus of the observed changes. Therefore, an accurate and multidisciplinary diagnosis is required.

Spelling errors reveal underlying sequential and spatial processing deficits in adults with dyslexia

ABSTRACT Recent studies showed that some adults with dyslexia have difficulty processing sequentially arranged information. In a companion study, this deficit manifested as low accuracy during a word pair comparison task involving same/different decisions when two words differed in their letter sequences. This sequential deficit was associated with left/right spatial letter confusion. In the present study, we found the same underlying difficulty with sequential and spatial letter processing during word spelling. Participants were the same 22 adults with dyslexia and 20 age- and gender-matched controls as in the companion study. In the spelling task, sequential error rates were higher in the dyslexia group, compared to the controls. Measures of accuracy of serial letter order during the spelling task and the word comparison task were correlated. Only three participants, each with dyslexia, produced left/right letter reversals during spelling. These were the same participants who produced left/right errors when naming single letters. They also had profound difficulty with sequential and left/right letter processing in the spelling and word comparison tasks, and they had the most severe spelling impairment. We conclude that this pervasive, persistent difficulty with sequential and spatial reversals contributes to a severe dyslexia subtype. In the dyslexia group as a whole, additional and separate sources of errors were underspecified word representations in long-term memory and homophone errors that likely represent language-based deficits in word knowledge. In the participants, these three factors (sequential/spatial letter confusion, underspecified word form representation, language-based deficits) occurred either as single factors or in combination with each other.

Reading Skills in Deaf Subjects: Role of Psycholinguistic Factors and Global Influences in Affecting Reading Performance

The present study examined the role of psycholinguistic variables, as well as the presence of a global factor, in modulating reading speed and accuracy in individuals with a severe hearing impairment. Thirteen deaf and thirteen hearing young adults who completed high school and were proficient in both oral lipreading and Italian sign language were examined and compared to a group of control subjects matched for gender, age and education. A wide spectrum of psycholinguistic variables affecting reading were examined, marking visual (letter confusability), sub-lexical (length, grapheme contextuality), lexical (frequency, N-size, stress) and semantic (age of acquisition and imageability) processes. Vocal reaction times (RT) in reading aloud single words were slower in deaf participants with respect to hearing subjects but they were affected by psycholinguistic variables in a very similar way than in the case of controls. Moreover, deaf individuals did not show a multiplicative effect as a function of word difficulty in their reading slowness but only a constant delay. Overall, the deficit shown by deaf participants was relatively limited and not associated to specific cognitive processes. This finding is in keeping with the idea that at least some individuals with a severe hearing impairment may reach reasonably high levels of word decoding.

Visual letter similarity effects during sentence reading: Evidence from the boundary technique

The study of how the cognitive system encodes letter identities from the visual input has received much attention in models of visual word recognition but it has typically been overlooked in models of eye movement control in reading. Here we examined how visual letter similarity affects early word processing during reading using Rayner's (1975) boundary change technique in which the parafoveal preview of the target word was either identical (e.g., frito-frito [fried]) or a one-letter-different nonword (e.g., frjto-frito vs. frgto-frito). Critically, the substituted letter in the nonword was visually similar (based on letter confusability norms) or visually dissimilar. Results showed shorter viewing times on the target word when the parafoveal preview was visually similar than when it was visually dissimilar. Thus, visual letter similarity modulates the integration of parafoveal and foveal information during sentence reading. Future implementations of models of eye movement control in reading should incorporate a more developed orthographic-lexical module to capture these effects.

Defining letter similarity

In letter identification, confusion probabilities are often used to define letter similarity. The goal of this study is to develop a universal, objective method to quantify letter similarity. Since letter similarity may be associated with the number of similar features shared by the letter pair, we started with identifying 22 potential letter features that appear universally across everyday fonts. A san-serif font, Century Gothic, was used for letter feature analysis. Only lowercase letters were considered. Customized Matlab scripts were used to process letter images and to detect and quantify letter features for each letter, following which similarity score between each pair of letters was calculated. There were 22 sets of similarity scores, one for each feature. To assess the amount of variation in letter confusion probability accounted for by the similarity scores, we performed linear regression analyses (considering only the linear terms). Four confusion matrices measured with different fonts under different testing conditions (Bouma, 1971; Geyer, 1977; McGraw et al., 1994) were examined. Despite the usage of different fonts in calculating similarity scores and obtaining confusion matrices, the best fitting models explained about 30% of the variability of letter confusion across the four confusion matrices. Ten letter features (e.g., number of separated parts, parallelism, and closed area) consistently showed significant contributions to the errors in letter identification. These findings suggested that defining letter similarity in a universal, objective way is feasible. Meeting abstract presented at VSS 2017

A crowdful of letters: Disentangling the role of similarity, eccentricity and spatial frequencies in letter crowding

The present study investigated the joint impact of target-flanker similarity and of spatial frequency content on the crowding effect in letter identification. We presented spatial frequency filtered letters to neurologically intact non-dyslexic readers while manipulating target-flanker distance, target eccentricity and target-flanker confusability (letter similarity metric based on published letter confusion matrices). The results show that high target-flanker confusability magnifies crowding. They also reveal an intricate pattern of interactions of the spatial frequency content of the stimuli with target eccentricity, flanker distance and similarity. The findings are congruent with the notion that crowding results from the inappropriate pooling of target and flanker features and that this integration is more likely to match a response template at a subsequent decision stage with similar than dissimilar flankers. In addition, the evidence suggests that crowding from similar flankers is biased towards relatively high spatial frequencies and that crowding shifts towards lower spatial frequencies as target eccentricity is increased.

Different aberrations raise contrast thresholds for single-letter identification in line with their effect on cross-correlation-based confusability

We previously showed that different types of aberration defocus, coma, and secondary astigmatism affect reading performance via different mechanisms. In this paper, we show the contrary result that, for identification of isolated letters, the effects of rendering different types of aberration can be described by a single cross-correlation-based metric. Aberrations reduce the effective resolution of an optical system, quantified by the high-frequency fall-off of the modulation transfer function. They additionally cause spatial-frequency-dependent phase and contrast changes, which have a size-dependent effect on letter forms. We used contrast threshold as our performance measure, instead of distance acuity, to separate the effects of form alterations from those of resolution limits. This measure is additionally appropriate in comparing single-letter-based performance to reading at a fixed distance. The relationship between a cross-correlation-based measure of letter confusability and performance was the same for all three types of aberration. For reading, we had found a different relationship for coma than for defocus and secondary astigmatism. We conclude that even when two tasks--letter identification and reading--use the same component stimulus set, the combination of multiple letters in a reading task produces functional differences between the effects of these aberrations that are not present for isolated letters.

Quantifying error distributions in crowding

When multiple objects are in close proximity, observers have difficulty identifying them individually. Two classes of theories aim to account for this crowding phenomenon: spatial pooling and spatial substitution. Variations of these accounts predict different patterns of errors in crowded displays. Here we aim to characterize the kinds of errors that people make during crowding by comparing a number of error models across three experiments in which we manipulate flanker spacing, display eccentricity, and precueing duration. We find that both spatial intrusions and individual letter confusions play a considerable role in errors. Moreover, we find no evidence that a naïve pooling model that predicts errors based on a nonadditive combination of target and flankers explains errors better than an independent intrusion model (indeed, in our data, an independent intrusion model is slightly, but significantly, better). Finally, we find that manipulating trial difficulty in any way (spacing, eccentricity, or precueing) produces homogenous changes in error distributions. Together, these results provide quantitative baselines for predictive models of crowding errors, suggest that pooling and spatial substitution models are difficult to tease apart, and imply that manipulations of crowding all influence a common mechanism that impacts subject performance.

Overcoming the effect of letter confusability in letter-by-letter reading: A rehabilitation study

Patients who read in a letter-by-letter manner can demonstrate effects of lexical variables when reading words comprised of low confusability letters, suggesting the capacity to process low-confusability words in parallel across the letters (Fiset, Arguin, & McCabe, 2006). Here a series of experiments is presented investigating letter confusability effects in MAH, a patient with expressive and receptive aphasia who shows reduced reading accuracy with longer words, and DM, a relatively “pure” alexic patient. Two rehabilitation studies were employed: (i) a word-level therapy and (ii) a letter-level therapy designed to improve discrimination of individual letters. The word-level treatment produced generalised improvement to low-confusability words only, but the serial processing treatment produced improvement on both high and low confusability words. The results add support to the hypothesis that letter confusability plays a key role in letter-by-letter reading, and suggest that a rehabilitation method aimed at reducing ambiguities in letter identification may be particularly effective for treating letter-by-letter reading.

Modelling normal and impaired letter recognition: Implications for understanding pure alexic reading

Letter recognition is the foundation of the human reading system. Despite this, it tends to receive little attention in computational modelling of single word reading. Here we present a model that can be trained to recognise letters in various spatial transformations. When presented with degraded stimuli the model makes letter confusion errors that correlate with human confusability data. Analyses of the internal representations of the model suggest that a small set of learned visual feature detectors support the recognition of both upper case and lower case letters in various fonts and transformations. We postulated that a damaged version of the model might be expected to act in a similar manner to patients suffering from pure alexia. Summed error score generated from the model was found to be a very good predictor of the reading times of pure alexic patients, outperforming simple word length, and accounting for 47% of the variance. These findings are consistent with a hypothesis suggesting that impaired visual processing is a key to understanding the strong word-length effects found in pure alexic patients.

Spatial Frequency and Similarity Modulate Crowding in Letter Identification

Visual crowding, which impairs our ability to accurately identify a target stimulus when surrounded by flankers, is ubiquitous across a wide variety of stimulus classes. Target eccentricity and target-flanker distance constitute fundamental factors in crowding. Target-flanker similarity appears as another key factor based on findings obtained with non-linguistic stimuli. The present study investigated the impact of these factors in conjunction with spatial frequency (SF) content on single letter identification performance. We presented SF filtered letters to neurologically intact nondyslexic readers while manipulating target-flanker distance, target eccentricity and target-flanker similarity (metric based on published letter confusion matrices). SF filtering conditions were broadband, low-pass, high-pass and hybrid (i.e. medium SFs, known as optimal for letter recognition, removed from the stimulus). These conditions were matched on overall contrast energy. Participants were required to identify the target letter as fast and as accurately as possible. The results show that high target-flanker similarity enhances crowding, i.e. the joint effects of distance and eccentricity. This extends past findings on the impact of similarity on crowding to the visual identification of linguistic materials. Most importantly, the magnitude of the crowding effect is greatest with low-pass filtering, followed by hybrids, high-pass, and broadband, with all pairwise contrasts significant. We conclude that: 1- medium SFs provide optimal protection from crowding in letter recognition; 2- when medium SFs are absent from the stimulus, low SFs magnify crowding and high SFs protect against it, most likely through their opposite impact on the availability of distinctive feature information.

Can positional averaging explain crowded letter confusions?

Can positional averaging explain crowded letter confusions?

Subsyllabic structure reflected in letter confusability effects in Korean word recognition

Korean subsyllabic structure was investigated by observing the pattern of responses arising from letter transpositions within a syllable in the Hangul script. Experiment 1 revealed no confusions when the onset and coda of one syllable of a disyllabic word were transposed. This was also the case in Experiment 2, where the transposition took place within a syllable having a coda composed of two consonants. However, confusion with the baseword was observed when the two consonants within the complex coda were themselves transposed. These results are taken to support the view that Hangul (and possibly all concatenating orthographic scripts) is processed based on its onset, vowel, and coda structure.

A comunicação visual de bulas de remédios: análise ergonômica da diagramação e forma tipográfica com pessoas de terceira idade

A comunicao visual o meio necessrio para transmisso de informaes. Considerando-se que as bulas de remdios oferecem dificuldades de legibilidade para o consumidor da terceira idade prope-se uma anlise de sua composio grfica da bula de remdio feita por investigao ergonmica textual quanto sua adequao tipogrfica e de diagramao. O estudo realizou pesquisa descritiva com anlise da bula de medicamento e de duas coletas de dados por entrevista individual com pessoas acima de 65 anos. A anlise da bula do Medicamento X, conforme fatores de legibilidade, apresenta inadequao quanto confuso entre letras e seu tamanho reduzido para a distncia de leitura que so combinados com as alteraes visuais do envelhecimento. A primeira coleta confirma essas dificuldades de leitura da bula do Medicamento X. A segunda coleta de dados consistiu da apresentao da bula do Medicamento X comparada com dois modelos que se diferenciaram quanto tipografia - Arial e Times New Roman, porm, com uma mesma diagramao, obedecendo os fatores de legibilidade de texto de Dull (1995) . Os resultados de melhor legibilidade para a bula indicam o modelo com tipo Arial. Conclui-se pela necessidade de equilbrio entre diagramao e tipografia para uma comunicao visual de bulas de remdios. [ Download ]

The relationship between visual crowding and letter confusability: Towards an understanding of dyslexia in posterior cortical atrophy

Visual crowding is a form of masking in which target identification is hindered by excessive feature integration from other stimuli in the vicinity. It has previously been suggested that excessive visual crowding constitutes one specific form of early-visual-processing deficit, which may be observed in individuals with posterior cortical atrophy (PCA). This study investigated whether excessive visual crowding plays a significant role in the acquired dyslexia of two PCA patients, whose reading was characterized by visual paralexias. The patients were administered a series of letter, flanked letter, and word recognition tasks, and the effects of letter spacing and letter confusability upon response accuracy and latency were measured. In both patients, the results showed (a) evidence of excessive visual crowding, (b) a significant interaction between letter spacing and confusability on flanked letter identification tasks, and (c) effects of letter confusability affecting flanked but not unflanked letter identification. However, only mild improvements in reading accuracy were achieved in the experimental manipulations of interletter spacing within words because these manipulations had a dual effect: Increasing spacing improved individual letter identification but damaged whole-word form and/or parallel letter processing. We consider the implications of these results for the characterization of dyslexia in PCA, the design of reading rehabilitation strategies, and the relationship between visual crowding and letter confusability. In particular, we argue that the reading deficits observed in our patients cannot be accounted for solely in terms of a very low signal-to-noise ratio for letter identification, and that an additional crowding deficit is implicated in which excessive integration of fundamental letter features leads to the formation of incorrect letter percepts.

Using geometric moments to explain human letter recognition near the acuity limit

When the size of a letter stimulus is near the visual acuity limit of a human subject, details of the stimulus become unavailable due to ocular optical and neural filtering. In this study we tested the hypothesis that letter recognition near the acuity limit is dependent on more global features, which could be parsimoniously described by a few easy-to-visualize and perceptually meaningful low-order geometric moments (i.e., the ink area, variance, skewness, and kurtosis). We constructed confusion matrices from a large set of data (approximately 110,000 trials) for recognition of English letters and Chinese characters of various spatial complexities near their acuity limits. We found that a major portion of letter confusions reported by human subjects could be accounted for by a geometric moment model, in which letter confusions were quantified in a space defined by low-order geometric moments. This geometric moment model is universally applicable to recognition of visual patterns of various complexities near their acuity limits.

Early literacy in Arabic: An intervention study among Israeli Palestinian kindergartners

ABSTRACTArabic Literacy acquisition was studied among Israeli Palestinian low socioeconomic status kindergartners within the framework of an intervention study, implemented by teachers. On pretest, letter naming, alphabetic awareness, and phonological awareness were very low. Whereas the comparison group hardly progressed throughout the year, the intervention group progressed substantially on all three skills. The diglossic nature of the Arabic letter name system was manifested in children's transition from a mixture of two systems to preference for standard over colloquial names following the intervention. As in other alphabets, visual similarity and adjacency increased letter confusability. The unique features of Arabic literacy are discussed.