The effect of contrast on reading speed in dyslexia

Room to read: The effect of extra-large letter spacing and coloured overlays on reading speed and accuracy in adolescents with dyslexia

BACKGROUND

Coloured overlay and extra-large letter spacing may improve reading speed and accuracy in individuals with dyslexia; however, research has yet to identify which types of reading errors are diminished.

AIM

To determine the impact of extra-large letter spacing and colour overlay on reading and assess the impact of both interventions on reading errors.

SAMPLE

Thirty-two dyslexic children were matched on age, verbal and non-verbal IQ with 27 children with no diagnosis of dyslexia. The average age of each group was 13 years.

METHOD

Participants read four texts with either standard or extra-large letter spacing with or without a coloured overlay.

RESULTS

Extra-large letter spacing significantly improved reading speed more substantially for the dyslexia group. In addition, extra-large letters significantly reduced the number of missed word errors made by the dyslexia group. In contrast, coloured overlays did not significantly impact reading speed or the reduction of errors.

CONCLUSION

Increasing letter spacing is an effective way for teachers to improve reading skills in students with dyslexia.

Challenges in Reading Arabic among Children with Dyslexia

SIGNIFICANCE

There are limited studies assessing reading performance and children's difficulties with dyslexia especially when reading Arabic, a language that has a substantially different script from English and other Latin-based languages.

PURPOSE

This study aimed to (1) measure reading performance in children with dyslexia by acuity level and (2) conduct an indirect comparison between the effects of dyslexia on Arabic versus English readers.

METHODS

Twenty children aged 9 to 12 years with dyslexia and 30 controls aged 9 to 11 years were included in the study. Reading performance was evaluated using maximum reading speed, reading acuity, and critical print size (CPS). Two Arabic charts, the Balsam Alabdulkader-Leat chart and the International Reading Speed Texts chart, were used to evaluate reading performance. The number of errors was calculated and plotted against print size.

RESULTS

ANOVA revealed a significant difference between the two groups in all reading performance measures (P < .05). Reading speed for children with dyslexia was significantly lower than that for the control group (33 vs. 90 standard-length words per minute). Critical print sizes were 0.25 and 0.10 logMAR for children with dyslexia and the control group, respectively. Reading acuity was worse for children with dyslexia in comparison with the control group. Error number above the CPS was significantly higher in children with dyslexia than in the control group.

CONCLUSIONS

Reading speed measures were lower for children with dyslexia compared with controls. Children with dyslexia required larger CPS to read at their maximum speed, indicating that larger print sizes may improve reading with greater speed. The difference in reading performance measures between controls and children with dyslexia is higher when reading Arabic than when reading English. This suggests that the intricate Arabic script and crowding may more strongly affect children with dyslexia reading Arabic.

Individuals with dyslexia use a different visual sampling strategy to read text

Individuals with dyslexia present with reading-related deficits including inaccurate and/or less fluent word recognition and poor decoding abilities. Slow reading speed and worse text comprehension can occur as secondary consequences of these deficits. Reports of visual symptoms such as atypical eye movements during reading gave rise to a search for these deficits' underlying mechanisms. This study sought to replicate established behavioral deficits in reading and cognitive processing speed while investigating their underlying mechanisms in more detail by developing a comprehensive profile of eye movements specific to reading in adult dyslexia. Using a validated standardized reading assessment, our findings confirm a reading speed deficit among adults with dyslexia. We observed different eye movements in readers with dyslexia across numerous eye movement metrics including the duration of a stop (i.e., fixation), the length of jumps (i.e., saccades), and the number of times a reader's eyes expressed a jump atypical for reading. We conclude that individuals with dyslexia visually sample written information in a laborious and more effortful manner that is fundamentally different from those without dyslexia. Our findings suggest a mix of aberrant cognitive linguistic and oculomotor processes being present in adults with dyslexia.

The effects of gender and academic achievement on reading fluency among Year 2 Malaysian school children

OBJECTIVE

Language disorders can affect reading skills contributing to poor academic achievements. As such, it is vital for speech language pathologists to identify the potential language-based reading problems among children. To achieve this, specific reading assessments should be developed and studied. Thus, the present study aimed to determine the effects of gender and academic achievement on oral reading fluency (ORF) and silent reading fluency (SRF) among Year 2 Malaysian children.

METHODS

In this study that employed a comparative design, fifty-nine typically developing Malaysian children (24 boys, aged from 8 years, 0 months to 8 years, 11 months) were enrolled. They were chosen from three different classrooms (consisting of high achieving, medium achieving and low achieving students, respectively) in a primary school. Their ORF and SRF skills were assessed according to the established methods.

RESULTS

As revealed by two-way ANOVA results, both ORF and SRF scores were found to be comparable between boys and girls (p > 0.05). In contrast, ORF and SRF results between the three classrooms were significantly different from each other (p < 0.05).

CONCLUSION

The present study provides the first report on oral and silent reading fluency skills among Year 2 Malaysian school children. While the gender effect was insignificant, low achieving students showed poorer reading fluency skills. The preliminary normative data for ORF and SRF provided by the present study are beneficial for future research applications.

Extending the MNREAD sentence corpus: Computer-generated sentences for measuring visual performance in reading

The MNREAD chart consists of standardized sentences printed at 19 sizes in 0.1 logMAR steps. There are 95 sentences distributed across the five English versions of the chart. However, there is a demand for a much larger number of sentences: for clinical research requiring repeated measures, and for new vision tests that use multiple trials at each print size. This paper describes a new sentence generator that has produced over nine million sentences that fit the MNREAD constraints, and demonstrates that reading performance with these new sentences is comparable to that obtained with the original MNREAD sentences. We measured reading performance with the original MNREAD sentences, two sets of our new sentences, and sentences with shuffled word order. Reading-speed versus print-size curves were obtained for each sentence set from 14 readers with normal vision at two levels of blur (intended to simulate acuity loss in low vision) and with unblurred text. We found no significant differences between the new and original sentences in reading acuity and critical print size across all levels of blur. Maximum reading speed was 7% slower with the new sentences than with the original sentences. Shuffled sentences yielded slower maximum reading speeds and larger reading acuities than the other sentences. Overall, measures of reading performance with the new sentences are similar to those obtained with the original MNREAD sentences. Our sentence generator substantially expands the reading materials for clinical research on reading vision using the MNREAD test, and opens up new possibilities for measuring how text parameters affect reading.

The effects of letter spacing and coloured overlays on reading speed and accuracy in adult dyslexia

BACKGROUND

Zorzi et al. (2012, Proc. Natl. Acad. Sci. U.S.A., 109, 11455) found evidence that extra-large letter spacing aids children with dyslexia, but the evidence for the coloured overlays is contradictory (e.g., Henderson et al., 2013, J. Res. Special Educ. Needs, 13, 57; Wilkins, 2002, Ophthalmic Physiol. Opt., 22, 448), and possible combined advantages have not been identified.

AIMS

To investigate whether extra-large letter spacing or coloured overlays can alleviate reading problems in dyslexic adults.

SAMPLE

The participants were 24 dyslexic and 24 non-dyslexic university students, matched for age and fluid intelligence.

METHODS

The reading speed and the errors made by a dyslexic and a control group were measured in four conditions: with and without coloured overlays and with normally and largely spaced texts.

RESULTS

Large letter spacing improves the reading speed in general, as well as improves the reading accuracy in dyslexic readers.

CONCLUSIONS

The results support the positive effect of letter spacing on reading performance.

Factors affecting crowded acuity: eccentricity and contrast

PURPOSE

Acuity measurement is a fundamental method to assess visual performance in the clinic. Little is known about how acuity measured in the presence of neighboring letters, as in the case of letter charts, changes with contrast and with nonfoveal viewing. This information is crucial for acuity measurement using low-contrast charts and when patients cannot use their fovea. In this study, we evaluated how optotype acuity, with and without flankers, is affected by contrast and eccentricity.

METHODS

Five young adults with normal vision identified the orientation of a Tumbling-E presented alone or in the presence of four flanking Tumbling-Es. Edge-to-edge letter spacing ranged from 1 to 20 bar widths. Stimuli were presented on a white background for 150 ms with Weber contrast ranging from -2.5% to -99%. Flankers had the same size and contrast as the target. Testings were performed at the fovea, 3°, 5°, and 10° in the inferior visual field.

RESULTS

When plotted as a function of letter spacing, acuity remains unaffected by the presence of flankers until the flankers are within the critical spacing, which averages an edge-to-edge spacing of 4.4 bar widths at the fovea and approximately 16 bar widths at all three eccentricities. Critical spacing decreases with a reduction in contrast. When plotted as a function of contrast, acuity only worsens when the contrast falls below approximately 24% at the fovea and 17% in the periphery, for flanked and unflanked conditions alike.

CONCLUSIONS

The letter spacing on conventional letter charts exceeds the critical spacing for acuity measurement at the fovea, at all contrast levels. Thus, these charts are appropriate for assessing foveal acuity. In the periphery, the critical spacing is larger than the letter spacing on conventional charts. Consequently, these charts may underestimate the acuity measured in the periphery because of the effects of crowding.

Influence of mild cognitive impairment on visual word recognition

The present study examined the effects of normal aging and mild cognitive impairment (MCI) on visual word recognition. Madden et al. (1999) reported evidence of general slowing of cognitive processes in Alzheimer's disease (AD) patients relative to younger adults and healthy older adults using a lexical decision task. It was of interest to determine whether similar effects would be observed in MCI patients relative to healthy younger and older adults. We extended the lexical decision task paradigm developed by Allen et al. (2004b) on younger adults to an examination of the effect(s) of MCI on visual word recognition. Results from the present study showed that healthy older adults and MCI patients performed similarly. That is, both groups took longer than younger adults to process words presented in mixed-case than in consistent-case letters. Mild cognitive impairment patients, however, responded significantly more slowly than healthy older adults across all lexical decision task conditions and showed a trend toward larger case-mixing effects than healthy older adults, which suggests that MCI may result in poorer analytic processing ability. Based on the current findings, evidence of a generalized slowing of cognitive processes using a standard lexical decision task can be expanded to include not only AD patients, but also the preclinical stages of the disease as well.

Computerized screening for visual stress in children with dyslexia

Visual stress-a condition in which unpleasant visual symptoms are experienced when reading-has been reported to be more prevalent in dyslexic individuals but at the present time the relationship between dyslexia and visual stress remains controversial. ViSS, a computerized visual stress screener that incorporates reading-like visual search, has recently shown promise in studies with unselected samples of primary and secondary school children. This study investigated the use of ViSS with dyslexic children. Dyslexic children identified as having high visual stress showed significantly higher per cent increases in reading rate with a coloured overlay and reported significantly higher critical symptoms of visual stress, compared to dyslexic children with low visual stress. The same results were found for reading-age controls, indicating that ViSS can be equally effective with normal readers as well as with children with dyslexia. Compared to reading-age controls, dyslexic children were found to have significantly higher susceptibility to visual stress, significantly larger per cent increases in reading rate with an overlay, and significantly higher critical and non-critical symptoms of visual stress. Extrapolated to unselected population samples, the data also suggest that visual stress is more likely to be found in people with dyslexia than in people who do not have dyslexia. These results, which point to an important link between the two conditions, are discussed in relation to current theories that attribute visual stress to either a magnocellular dysfunction or cortical hyperexcitability.

Isolating the impact of visual perception on dyslexics' reading ability

A large body of data suggests that phonological deficits play an important causal role in dyslexics' reading difficulties. The functional role of visual impairments is still highly debated. Many recent studies have shown clear visual deficits in large subgroups of dyslexics. However, the relationship between these deficits and visual routines required for reading is not clear. To assess the direct contribution of visual factors to dyslexics' slower and less accurate reading, we composed a task that was similar to single word reading in its basic visual characteristics, but had none of the other (phonological, morphological, semantic, etc.) aspects of reading. Young adult dyslexics, with average or above general cognitive abilities, and controls matched for age and cognitive skills participated in the study. We measured both SOA and contrast thresholds for identifying unfamiliar letters. Letters were chosen from an alphabet graphically similar to Hebrew and English (a subset of Georgian letters), but unfamiliar to the subjects. Effects of decreasing letter size, increasing letter crowding (by adding a flanker letter on each side) and adding white noise, were measured. Dyslexics performed as well as controls under all test conditions, and had similar effect sizes. We thus conclude that, despite the data showing that dyslexics have marked difficulties with single word reading, the cause of these difficulties is not a visual processing deficit.

Assessing the role of different spatial frequencies in word perception by good and poor readers

Numerous studies indicate that dyslexic and nondyslexic individuals exhibit different patterns of sensitivity to spatial frequency. However, the extension of this effect to normal (nondyslexic) adults of good and poor reading abilities and the role played by different spatial frequencies in word perception have yet to be determined. In this study, using normal (nondyslexic) adults, we assessed reading ability, spatial frequency sensitivity, and perception of spatially filtered words and nonwords (using a two-alternative forced choice paradigm to avoid artifactual influences of nonperceptual guesswork). Good and poor readers showed different patterns of spatial frequency sensitivity. However, no differences in accuracy of word and nonword perception were found between good and poor readers, despite their differences in spatial frequency sensitivity. Indeed, both reading abilities showed the same superior perceptibility for spatially filtered words over nonwords across different spatial frequency bands. These findings indicate that spatial frequency sensitivity differences extend to normal (nondyslexic) adult readers and that a range of spatial frequencies can be used for word perception by good and poor readers. However, spatial frequency sensitivity may not accurately reveal an individual's ability to perceive words.

The effect of print size on reading speed in dyslexia

This article details a study which predicted that across a wide range of print sizes dyslexic reading would follow the same curve shape as skilled reading, with constant reading rates across large print sizes and a sharp decline in reading rates below a critical print size. It also predicted that dyslexic readers would require larger critical print sizes to attain their maximum reading speeds, following the letter position coding deficit hypothesis. Reading speed was measured across twelve print sizes ranging from Snellen equivalents of 20/12 to 20/200 letter sizes for a group of dyslexic readers in Grades 2 to 4 (aged 7 to 10 years), and for non-dyslexic readers in Grades 1 to 3 (aged 6 to 8 years). The groups were equated for word reading ability. Results confirmed that reading rate-by-print size curves followed the same two-limbed shape for dyslexic and non-dyslexic readers. Dyslexic reading curves showed higher critical print sizes and shallower reading rate-by-print size slopes below the critical print size, consistent with the hypothesis of a letter-position coding deficit. Non-dyslexic reading curves also showed a decrease of critical print size with age. A developmental lag model of dyslexic reading does not account for the results, since the regression of critical print size on maximum reading rate differed between groups.

Use of the Hermann grid illusion in the measurement of contrast perception in dyslexia

We measured contrast thresholds for perception of the Hermann grid illusion, using different contrast polarities and mean luminances, in dyslexics and non-dyslexics. Both groups of subjects gave significantly lower thresholds with grids having dark squares and light paths, but there was no significant threshold difference between groups. Perceived strength of illusion was also measured in grids at suprathreshold contrast levels. Dyslexics perceived the illusion to be significantly stronger than non-dyslexics when the grid had light paths and low luminance.

On the use of red stimuli to isolate magnocellular responses in psychophysical experiments: A perspective

Neurophysiological recordings have shown that activity of magnocellular neurons may be reduced by red backgrounds. This has led some researchers to use red light, or red filters, in attempts to determine the magnocellular contribution to psychophysical tasks. This requires that red light not affect parvocellular neurons, or at least that it is possible to control for the effect on the parvocellular system by using other colors. The present report investigates these assumptions by calculating the effect of red, green, and blue filters on the three cone pigments and on the four parvocellular color-opponent cell mechanisms. It is found that a red filter has a large effect on the long- and middle-wavelength cone pigments and on the red–green color-opponent mechanisms. A green filter, on the other hand, has little effect. A blue filter has a fairly pronounced effect but this effect is distinctly different from that of the red filter. These results indicate that one ought not rely upon red light to isolate magnocellular activity in psychological experiments. The results also indicate that it is difficult to use colors other than red to control for the effect of this color on the parvocellular system.

Crowding effects on word identification in developmental dyslexia

The effect of crowding on the identification of words was examined in normal readers and subjects with developmental dyslexia. In Experiment 1, a matching task was used. Words were presented either alone or embedded in other words. Vocal reaction times (RT) of dyslexics were slower and more sensitive to the presence of the surrounding stimuli than those of control subjects. Similar results were obtained in a control experiment using the same task for strings of symbols (isolated or crowded) instead of words. These data indicate that differences in crowding in control and dyslexic subjects arise at a pre-linguistic level. In Experiment 2, vocal RTs to word reading were measured. Two conditions putatively reducing the effect of crowding were tested: increasing inter-letter spacing and blurring. A moderate increase of inter-letter spacing produced faster vocal RTs in dyslexics, while no effect was present in normal controls. Moderate blurring of stimuli did not change dyslexics' RTs, while normal readers became slower. Group and individual results are discussed to evaluate the extent to which crowding contributes to the genesis of developmental dyslexia.