Effect of pattern complexity on the visual span for Chinese and alphabet characters

Orthographic character complexity modulates dynamic neural activity in skilled handwriting

Handwriting is an outstanding case of a highly complex and efficient fine motor skill. However, little is known about its neural underpinnings during continuous handwriting production. In the present study, we examined the effects of orthographic character complexity (i.e. the stroke number of a Chinese character) on both neural and behavioural activities during an EEG-based naturalistic fluent sentence-handwriting task from 102 adult Chinese native speakers. For each written character, the interval between finishing the preceding character and its onset (inter-character interval) as well as the amplitudes of the onset-synchronized event-related potential (ERP) in pre- and post-onset time windows was defined as dependent variables. The effects of character complexity and other confounding factors were analysed with linear mixed models. Character complexity increased the inter-character interval and significantly affected ERP amplitudes in both pre- and post-onset time windows. The ERP pattern in the pre-event time window exhibited a dipole-like activation in the left motor cortex, and its amplitude increased with character complexity in line with the documented relationship between the lateralized readiness potential and motor complexity. This study demonstrates the feasibility of studying neurocognitive processes in complex naturalistic motor tasks and extends our knowledge about the dynamic pattern of handwriting-related neural activities.

Column setting and text justification influence return-sweep eye movement behavior during Chinese multi-line reading

People regularly read multi-line texts in different formats and publishers, internationally, must decide how to present text to make reading most effective and efficient. Relatively few studies have examined multi-line reading, and fewer still Chinese multi-line reading. Here, we examined whether texts presented in single or double columns, and either left-justified or fully-justified affect Chinese reading. Text format had minimal influence on overall reading time; however, it significantly impacted return-sweeps (large saccades moving the eyes from the end of one line of text to the beginning of the next). Return-sweeps were launched and landed further away from margins and involved more corrective saccades in single- than double-column format. For left- compared to fully-justified format, return-sweeps were launched and landed closer to margins. More corrective saccades also occurred. Our results showed more efficient return-sweep behavior for fully- than left-justified text. Moreover, there were clear trade-off effects such that formats requiring increased numbers of shorter return-sweeps produced more accurate targeting and reduced numbers of corrective fixations, whereas formats requiring reduced numbers of longer return-sweeps caused less accurate targeting and an increased rate of corrective fixations. Overall, our results demonstrate that text formats substantially affect return-sweep eye movement behavior during Chinese reading without affecting efficiency and effectiveness, that is, the overall time it takes to read and understand the text.

Simplification Is Not Dominant in the Evolution of Chinese Characters

Linguistic systems are hypothesised to be shaped by pressures towards communicative efficiency that drive processes of simplification. A longstanding illustration of this idea is the claim that Chinese characters have progressively simplified over time. Here we test this claim by analyzing a dataset with more than half a million images of Chinese characters spanning more than 3,000 years of recorded history. We find no consistent evidence of simplification through time, and contrary to popular belief we find that modern Chinese characters are higher in visual complexity than their earliest known counterparts. One plausible explanation for our findings is that simplicity trades off with distinctiveness, and that characters have become less simple because of pressures towards distinctiveness. Our findings are therefore compatible with functional accounts of language but highlight the diverse and sometimes counterintuitive ways in which linguistic systems are shaped by pressures for communicative efficiency.

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.

Cultural Differences in Face Recognition and Potential Underlying Mechanisms

The ability to recognize a face is crucial for the success of social interactions. Understanding the visual processes underlying this ability has been the focus of a long tradition of research. Recent advances in the field have revealed that individuals having different cultural backgrounds differ in the type of visual information they use for face processing. However, the mechanisms that underpin these differences remain unknown. Here, we revisit recent findings highlighting group differences in face processing. Then, we integrate these results in a model of visual categorization developed in the field of psychophysics: the RAP framework. On the basis of this framework, we discuss potential mechanisms, whether face-specific or not, that may underlie cross-cultural differences in face perception.

Perceptual expertise with Chinese characters predicts Chinese reading performance among Hong Kong Chinese children with developmental dyslexia

This study explores the theoretical proposal that developmental dyslexia involves a failure to develop perceptual expertise with words despite adequate education. Among a group of Hong Kong Chinese children diagnosed with developmental dyslexia, we investigated the relationship between Chinese word reading and perceptual expertise with Chinese characters. In a perceptual fluency task, the time of visual exposure to Chinese characters was manipulated and limited such that the speed of discrimination of a short sequence of Chinese characters at an accuracy level of 80% was estimated. Pair-wise correlations showed that perceptual fluency for characters predicted speeded and non-speeded word reading performance. Exploratory hierarchical regressions showed that perceptual fluency for characters accounted for 5.3% and 9.6% variance in speeded and non-speeded reading respectively, in addition to age, non-verbal IQ, phonological awareness, morphological awareness, rapid automatized naming (RAN) and perceptual fluency for digits. The findings suggest that perceptual expertise with words plays an important role in Chinese reading performance in developmental dyslexia, and that perceptual training is a potential remediation direction.

Number of flankers influences foveal crowding and contour interaction differently

Nearby flanking objects degrade visual resolution. If the flankers are similar to the acuity target, this influence is called crowding (CW), whereas if the flanking stimuli are simple bars then the phenomenon is known as contour interaction (CI). The aim of this study was to compare the influence of the number and position of flankers on foveal CW and CI to investigate possible differences in mechanism of these two effects. Five normal observers viewed single, foveally presented Sloan letters surrounded by 1, 2 or 4 flankers (either a Sloan letter or one-stroke-width bars), presented at several edge-to-edge separations. Single flankers were presented in the right, left, top or bottom position, 2 flankers were placed equally to the right and left or top and bottom of the central target, and 4 flankers were equally spaced in all four directions. Percent correct letter identification was determined for each type, number, position and separation of flankers and confusion matrices were constructed for separations equal to 20% and 100% letter width. Increasing the number of flankers caused an increase in the magnitude of both phenomena. CW showed a greater magnitude than CI for higher numbers of flankers. Analysis of confusion matrices suggests that in addition to the edge-to-edge interaction that appears to mediate CI, letter substitution and feature pooling contribute significantly to CW when higher numbers of flankers are presented. Foveal CW is more strongly influenced by an increase in the number of flankers than CI, which can be explained by the presence of additional interaction effects.

Cognitive Correlates of Reading Fluency in Chinese School-Aged Children

Previous studies have showed that reading fluency is strongly associated with cognitive skills, including rapid automatized naming, phonological awareness, orthographical awareness, and so on. However, these studies are largely based on alphabetic languages, and it remains unclear which cognitive factors contribute to the development of reading fluency in logographic Chinese, a language in which the graphic forms map onto morphemes (meaning) rather than phonemes. In Study 1, we tested 179 Chinese children aged 6 to 9 on a set of cognitive tasks as well as for word reading accuracy and sentence reading fluency. The results showed that rapid naming, writing fluency, and phonological awareness significantly predicted reading fluency in both beginning and intermediate readers. In addition, while the contribution of rapid naming and writing fluency increased with grades, the effect of phonological awareness decreased. In Study 2, we examined the role of visual crowding in reading fluency in a subgroup of 86 children and found that visual crowding accounted for the unique variance of individual differences in reading fluency. The findings reflect both universal and language-specific cognitive correlates of reading fluency and provide important implications for potentially effective treatment for individuals suffering from Chinese reading disabilities, particularly in terms of reading fluency.

Revealing similarities in the perceptual span of young and older Chinese readers

Older readers (aged 65+ years) of both alphabetic languages and character-based languages like Chinese read more slowly than their younger counterparts (aged 18-30 years). A possible explanation for this slowdown is that, due to age-related visual and cognitive declines, older readers have a smaller perceptual span and so acquire less information on each fixational pause. However, although aging effects on the perceptual span have been investigated for alphabetic languages, no such studies have been reported to date for character-based languages like Chinese. Accordingly, we investigated this issue in three experiments that used different gaze-contingent moving window paradigms to assess the perceptual span of young and older Chinese readers. In these experiments, text was shown either entirely as normal or normal only within a narrow region (window) comprising either the fixated word, the fixated word, and one word to its left, or the fixated word and either one or two words to its right. Characters outside these windows were replaced using a pattern mask (Experiment 1) or a visually similar character (Experiment 2), or blurred to render them unidentifiable (Experiment 3). Sentence reading times were overall longer for the older compared with the younger adults and differed systematically across display conditions. Crucially, however, the effects of display condition were essentially the same across the two age groups, indicating that the perceptual span for Chinese does not differ substantially for the older and young adults. We discuss these findings in relation to other evidence suggesting the perceptual span is preserved in older adulthood.

Effects of Normative Aging on Eye Movements during Reading

Substantial progress has been made in understanding the mostly detrimental effects of normative aging on eye movements during reading. This article provides a review of research on aging effects on eye movements during reading for different writing systems (i.e., alphabetic systems like English compared to non-alphabetic systems like Chinese), focused on appraising the importance of visual and cognitive factors, considering key methodological issues, and identifying vital questions that need to be addressed and topics for further investigation.

Visual span and cognitive factors affect Chinese reading speed

Visual span, which is the number of recognizable letters seen without moving the eyes, has been proven to impose a sensory limitation for alphabetic reading speed (Chung, 2011; Chung, Legge, & Cheung, 2004; Lee, Kwon, Legge, & Gefroh, 2010; Legge, Ahn, Klitz, & Luebker, 1997; Legge, Hooven, Klitz, Stephen Mansfield, & Tjan, 2002; D. Yu, Cheung, Legge, & Chung, 2010). However, little is known about the effects of visual span on Chinese reading performance. Of note, Chinese text differs greatly from that of the alphabetic writing system. There are no spaces between words, and readers are forced to utilize their lexical knowledge to segment Chinese characters into meaningful words, thus increasing the relative importance of cognitive/linguistic factors in reading performance. Therefore, the aim of the present study is to explore whether visual span and cognitive/linguistic factors have independent effects on Chinese reading speed. Visual span profiles, cognitive/linguistic factors indicated by word frequency, and Chinese sentence-reading performance were collected from 28 native Chinese-speaking subjects. We found that the visual-span size and cognitive/linguistic factors independently contributed to Chinese sentence-reading speed (all ps < 0.05). We concluded that both the visual-span size and cognitive/linguistic factors represented bottlenecks for Chinese sentence-reading speed.

Establishing a role for the visual complexity of linguistic stimuli in age-related reading difficulty: Evidence from eye movements during Chinese reading

Older adults experience greater difficulty compared to young adults during both alphabetic and nonalphabetic reading. However, while this age-related reading difficulty may be attributable to visual and cognitive declines in older adulthood, the underlying causes remain unclear. With the present research, we focused on effects related to the visual complexity of written language. Chinese is ideally suited to investigating such effects, as characters in this logographic writing system can vary substantially in complexity (in terms of their number of strokes, i.e., lines and dashes) while always occupying the same square area of space, so that this complexity is not confounded with word length. Nonreading studies suggests older adults have greater difficulty than young adults when recognizing characters with high compared to low numbers of strokes. The present research used measures of eye movements to investigate adult age differences in these effects during natural reading. Young adult (18-28 years) and older adult (65+ years) participants read sentences that included one of a pair of two-character target words matched for lexical frequency and contextual predictability, but composed of either high-complexity (>9 strokes) or low-complexity (≤7 strokes) characters. Typical patterns of age-related reading difficulty were observed. However, an effect of visual complexity in reading times for words was greater for the older than for the younger adults, due to the older readers experiencing greater difficulty identifying words containing many rather than few strokes. We interpret these findings in terms of the influence of subtle deficits in visual abilities on reading capabilities in older adulthood.

Aging Effects on the Visual Span for Alphabetic Stimuli

Background: The visual span (i.e., an estimate of the number of letters that can be recognized reliably on a single glance) is widely considered to impose an important sensory limitation on reading speed. With the present research, we investigated adult age differences in the visual span for alphabetic stimuli (i.e., Latin alphabetic letters), as aging effects on span size may make an important contribution to slower reading speeds in older adulthood. Method: A trigram task, in which sets of three letters were displayed randomly at specified locations to the right and left of a central fixation point, was used to estimate the size of the visual span for young (18-30 years) and older (65+years) adults while an eye tracker was used to ensure accurate central fixation during stimulus presentation. Participants also completed tests of visual acuity and visual crowding. Results: There were clear age differences in the size of the visual span. The older adults produced visual spans which were on average 1.2 letters smaller than the spans of young adults. However, both young and older adults produced spans smaller than those previously reported. In addition, span size correlated with measures of both visual acuity and measures of visual crowding. Conclusion: The findings show that the size of the visual span is smaller for older compared to young adults. The age-related reduction in span size is relatively small but may make a significant contribution to reduced parafoveal processing during natural reading so may play a role in the greater difficulty experienced by older adult readers. Moreover, these results highlight the importance of carefully controlling fixation location in visual span experiments.

Adult Age Differences in Eye Movements During Reading: The Evidence From Chinese

Objectives

Substantial evidence indicates that older readers of alphabetic languages (e.g., English and German) compensate for age-related reading difficulty by employing a more risky reading strategy in which words are skipped more frequently. The effects of healthy aging on reading behavior for nonalphabetic languages, like Chinese, are largely unknown, although this would reveal the extent to which age-related changes in reading strategy are universal. Accordingly, the present research used measures of eye movements to investigate adult age differences in Chinese reading.

Method

The eye movements of young (18-30 years) and older (60+ years) Chinese readers were recorded.

Results

The older adults exhibited typical patterns of age-related reading difficulty. But rather than employing a more risky reading strategy compared with the younger readers, the older adults read more carefully by skipping words infrequently, making shorter forward eye movements, and fixating closer to the beginnings of two-character target words in sentences.

Discussion

In contrast with the findings for alphabetic languages, older Chinese readers appear to compensate for age-related reading difficulty by employing a more careful reading strategy. Age-related changes in reading strategy therefore appear to be language specific, rather than universal, and may reflect the specific visual and linguistic requirements of the writing system.

Perceptual Learning of Visual Span Improves Chinese Reading Speed

Purpose

Evidence has indicated that the size of the visual span (the number of identifiable letters without movement of the eyes) and reading speed can be boosted through perceptual learning in alphabetic scripts. In this study, we investigated whether benefits of perceptual learning could be extended to visual-span size and sentence reading (all characters are presented at the same time) for Chinese characters and explored changes in sensory factors contributing to changes in visual-span size following training.

Methods

We randomly assigned 26 normally sighted subjects to either a control group (n = 13) or a training group (n = 13). Pre- and posttests were administered to evaluate visual-span profiles (VSPs) and reading speed. Training consisted of trigram (sequences of three characters) character-recognition trials over 4 consecutive days. VSPs are plots of recognition accuracy as a function of character position. Visual-span size was quantified as the area under VSPs in bits of information transmitted. A decomposition analysis of VSPs was used to quantify the effects of sensory factors (crowding and mislocation). We compared the size and sensory factors of visual span and reading speed following training.

Results

Following training, the visual-span size significantly increased by 11.7 bits, and reading speed increased by 50.8%. The decomposition analysis showed a significant reduction for crowding (-13.1 bits) but a minor increase in the magnitude of mislocation errors (1.46 bits) following training.

Conclusions

These results suggest that perceptual learning expands the visual-span size and further improves Chinese text sentence-reading speed, indicating that visual span may be a common sensory limitation on reading that can be overcome with practice.

Aging and Pattern Complexity Effects on the Visual Span: Evidence from Chinese Character Recognition

Research suggests that pattern complexity (number of strokes) limits the visual span for Chinese characters, and that this may have important consequences for reading. With the present research, we investigated age differences in the visual span for Chinese characters by presenting trigrams of low, medium or high complexity at various locations relative to a central point to young (18–30 years) and older (60+ years) adults. A sentence reading task was used to assess their reading speed. The results showed that span size was smaller for high complexity stimuli compared to low and medium complexity stimuli for both age groups, replicating previous findings with young adult participants. Our results additionally showed that this influence of pattern complexity was greater for the older than younger adults, such that while there was little age difference in span size for low and medium complexity stimuli, span size for high complexity stimuli was almost halved in size for the older compared to the young adults. Finally, our results showed that span size correlated with sentence reading speed, confirming previous findings taken as evidence that the visual span imposes perceptual limits on reading speed. We discuss these findings in relation to age-related difficulty reading Chinese.

Korean reading speed: Effects of print size and retinal eccentricity

Evaluating the effects of print size and retinal eccentricity on reading speed is important for identifying the constraints faced by people with central-field loss. Previous work on English reading showed that 1) reading speed increases with print size until a critical print size (CPS) is reached, and then remains constant at a maximum reading speed (MRS), and 2) as eccentricity increases, MRS decreases and CPS increases. Here we extend this work to Korean, a language with more complex orthography. We recruited 6 Korean native speakers (mean age = 22) and measured their reading speed in central vision (0°) and peripheral vision (10° in the lower field). 900 Korean sentences (average 8.25 words) were created with frequently-occurring beginner-level words, presented using a rapid serial visual presentation (RSVP) paradigm. Data for English reading were obtained from Chung, Mansfield & Legge, Vision Research, 1998, for comparison. MRS was similar for Korean and English at 0° (713 vs. 787 wpm), but decreased faster with eccentricity for Korean. CPS was larger for Korean than for English regardless of eccentricity, but increased with eccentricity similarly for both languages. From 0 to 10°, MRS decreased by a factor of 6.5 for Korean and 2.8 for English, and CPS increased by a factor of 11.7 for Korean and 10.2 for English. Korean reading speed is more affected by retinal eccentricity than English, likely due to additional within-character crowding from more complex orthography. Korean readers with central-field loss may experience more difficulty than English readers.

Fonts Designed for Macular Degeneration: Impact on Reading

Purpose

People with macular degeneration (MD) experience difficulties in reading due to central-field loss. Two new fonts, Eido and Maxular Rx, have been designed specifically for individuals with MD. We have compared reading performance of these new fonts with three mainstream fonts (Times-Roman, Courier, and Helvetica).

Methods

Subjects with MD (n = 19) and normally sighted subjects (n = 40) were tested with digital versions of the MNREAD test using the five fonts. Maximum reading speed (MRS), critical print size (CPS), and reading acuity (RA) were estimated to characterize reading performance. Physical properties of the fonts were quantified by interletter spacing and perimetric complexity.

Results

Reading with MD showed font differences in MRS, CPS, and RA. Compared with Helvetica and Times, Maxular Rx permitted both smaller CPS and RA, and Eido permitted smaller RA. However, the two new fonts presented no advantage over Courier. Spacing, but not Complexity, was a significant predictor of reading performance for subjects with MD.

Conclusions

The two fonts, designed specifically for MD, permit smaller print to be read, but provide no advantage over Courier.

Common constraints limit Korean and English character recognition in peripheral vision

The visual span refers to the number of adjacent characters that can be recognized in a single glance. It is viewed as a sensory bottleneck in reading for both normal and clinical populations. In peripheral vision, the visual span for English characters can be enlarged after training with a letter-recognition task. Here, we examined the transfer of training from Korean to English characters for a group of bilingual Korean native speakers. In the pre- and posttests, we measured visual spans for Korean characters and English letters. Training (1.5 hours × 4 days) consisted of repetitive visual-span measurements for Korean trigrams (strings of three characters). Our training enlarged the visual spans for Korean single characters and trigrams, and the benefit transferred to untrained English symbols. The improvement was largely due to a reduction of within-character and between-character crowding in Korean recognition, as well as between-letter crowding in English recognition. We also found a negative correlation between the size of the visual span and the average pattern complexity of the symbol set. Together, our results showed that the visual span is limited by common sensory (crowding) and physical (pattern complexity) factors regardless of the language script, providing evidence that the visual span reflects a universal bottleneck for text recognition.

Comparing the minimum spatial-frequency content for recognizing Chinese and alphabet characters

Visual blur is a common problem that causes difficulty in pattern recognition for normally sighted people under degraded viewing conditions (e.g., near the acuity limit, when defocused, or in fog) and also for people with impaired vision. For reliable identification, the spatial frequency content of an object needs to extend up to or exceed a minimum value in units of cycles per object, referred to as the critical spatial frequency. In this study, we investigated the critical spatial frequency for alphabet and Chinese characters, and examined the effect of pattern complexity. The stimuli were divided into seven categories based on their perimetric complexity, including the lowercase and uppercase alphabet letters, and five groups of Chinese characters. We found that the critical spatial frequency significantly increased with complexity, from 1.01 cycles per character for the simplest group to 2.00 cycles per character for the most complex group of Chinese characters. A second goal of the study was to test a space-bandwidth invariance hypothesis that would represent a tradeoff between the critical spatial frequency and the number of adjacent patterns that can be recognized at one time. We tested this hypothesis by comparing the critical spatial frequencies in cycles per character from the current study and visual-span sizes in number of characters (measured by Wang, He, & Legge, 2014) for sets of characters with different complexities. For the character size (1.2°) we used in the study, we found an invariant product of approximately 10 cycles, which may represent a capacity limitation on visual pattern recognition.

Age-related changes in crowding and reading speed

Crowding, the inability to recognize objects in clutter, is known to play a role in developmental changes in reading speed. Here, we investigated whether crowding also plays a role in age-related changes in reading speed. We recruited 18 young (mean age: 22.6 ± 3.5; range: 18~31) and 21 older adults (mean age: 58.2 ± 7.0; range: 50~73) with normal vision. Reading speed was measured with short blocks of text. The degree of crowding was determined by measuring crowding zone (the distance between a target and flankers required to yield a criterion recognition accuracy) and the size of the visual span (an uncrowded window in the visual field within which letters can be recognizable reliably). Measurements were made across the central 16-degree visual field using letter-recognition tasks. Our results showed that, compared to young adults, older adults exhibited significantly slower reading speed (a decrease by 30%) and larger crowding: an enlargement of crowding zone (an increase by 31%) and shrinkage of the visual span (a decrease by 6.25 bits). We also observed significant correlations between reading speed and each of the crowding measures. Our results suggest that crowding increases with age. Age-related changes in crowding may in part explain slower reading in older adults.

The effect of letter string length and report condition on letter recognition accuracy

PURPOSE

Letter sequence recognition accuracy has been postulated to be limited primarily by low-level visual factors. The influence of high level factors such as visual memory (load and decay) has been largely overlooked. This study provides insight into the role of these factors by investigating the interaction between letter sequence recognition accuracy, letter string length and report condition.

METHODS

Letter sequence recognition accuracy for trigrams and pentagrams were measured in 10 adult subjects for two report conditions. In the complete report condition subjects reported all 3 or all 5 letters comprising trigrams and pentagrams, respectively. In the partial report condition, subjects reported only a single letter in the trigram or pentagram. Letters were presented for 100ms and rendered in high contrast, using black lowercase Courier font that subtended 0.4° at the fixation distance of 0.57m.

RESULTS

Letter sequence recognition accuracy was consistently higher for trigrams compared to pentagrams especially for letter positions away from fixation. While partial report increased recognition accuracy in both string length conditions, the effect was larger for pentagrams, and most evident for the final letter positions within trigrams and pentagrams. The effect of partial report on recognition accuracy for the final letter positions increased as eccentricity increased away from fixation, and was independent of the inner/outer position of a letter.

CONCLUSIONS

Higher-level visual memory functions (memory load and decay) play a role in letter sequence recognition accuracy. There is also suggestion of additional delays imposed on memory encoding by crowded letter elements.

Learning to recognize letters in the periphery: Effects of repeated exposure, letter frequency, and letter complexity

Patients with central vision loss must rely on their peripheral vision for reading. Unfortunately, limitations of peripheral vision, such as crowding, pose significant challenges to letter recognition. As a result, there is a need for developing effective training methods for improving crowded letter recognition in the periphery. Several studies have shown that extensive practice with letter stimuli is beneficial to peripheral letter recognition. Here, we explore stimulus-related factors that might influence the effectiveness of peripheral letter recognition training. Specifically, we examined letter exposure (number of letter occurrences), frequency of letter use in English print, and letter complexity and evaluated their contributions to the amount of improvement observed in crowded letter recognition following training. We analyzed data collected across a range of training protocols. Using linear regression, we identified the best-fitting model and observed that all three stimulus-related factors contributed to improvement in peripheral letter recognition with letter exposure being the most important factor. As an important explanatory variable, pretest accuracy was included in the model as well to avoid estimate biases and was shown to have influence on the relationship between training improvement and letter exposure. When developing training protocols for peripheral letter recognition, it may be beneficial to not only consider the overall length of training, but also to tailor the number of stimulus occurrences for each letter according to its initial performance level, frequency, and complexity.

A New Font, Specifically Designed for Peripheral Vision, Improves Peripheral Letter and Word Recognition, but Not Eye-Mediated Reading Performance

Reading speed is dramatically reduced when readers cannot use their central vision. This is because low visual acuity and crowding negatively impact letter recognition in the periphery. In this study, we designed a new font (referred to as the Eido font) in order to reduce inter-letter similarity and consequently to increase peripheral letter recognition performance. We tested this font by running five experiments that compared the Eido font with the standard Courier font. Letter spacing and x-height were identical for the two monospaced fonts. Six normally-sighted subjects used exclusively their peripheral vision to run two aloud reading tasks (with eye movements), a letter recognition task (without eye movements), a word recognition task (without eye movements) and a lexical decision task. Results show that reading speed was not significantly different between the Eido and the Courier font when subjects had to read single sentences with a round simulated gaze-contingent central scotoma (10° diameter). In contrast, Eido significantly decreased perceptual errors in peripheral crowded letter recognition (-30% errors on average for letters briefly presented at 6° eccentricity) and in peripheral word recognition (-32% errors on average for words briefly presented at 6° eccentricity).

Effects of word frequency and visual complexity on eye movements of young and older Chinese readers

Research using alphabetic languages shows that, compared to young adults, older adults employ a risky reading strategy in which they are more likely to guess word identities and skip words to compensate for their slower processing of text. However, little is known about how ageing affects reading behaviour for naturally unspaced, logographic languages like Chinese. Accordingly, to assess the generality of age-related changes in reading strategy across different writing systems we undertook an eye movement investigation of adult age differences in Chinese reading. Participants read sentences containing a target word (a single Chinese character) that had a high or low frequency of usage and was constructed from either few or many character strokes, and so either visually simple or complex. Frequency and complexity produced similar patterns of influence for both age groups on skipping rates and fixation times for target words. Both groups therefore demonstrated sensitivity to these manipulations. But compared to the young adults, the older adults made more and longer fixations and more forward and backward eye movements overall. They also fixated the target words for longer, especially when these were visually complex. Crucially, the older adults skipped words less and made shorter progressive saccades. Therefore, in contrast with findings for alphabetic languages, older Chinese readers appear to use a careful reading strategy according to which they move their eyes cautiously along lines of text and skip words infrequently. We propose they use this more careful reading strategy to compensate for increased difficulty processing word boundaries in Chinese.

Comparing the visual spans for faces and letters

The visual span-the number of adjacent text letters that can be reliably recognized on one fixation-has been proposed as a sensory bottleneck that limits reading speed (Legge, Mansfield, & Chung, 2001). Like reading, searching for a face is an important daily task that involves pattern recognition. Is there a similar limitation on the number of faces that can be recognized in a single fixation? Here we report on a study in which we measured and compared the visual-span profiles for letter and face recognition. A serial two-stage model for pattern recognition was developed to interpret the data. The first stage is characterized by factors limiting recognition of isolated letters or faces, and the second stage represents the interfering effect of nearby stimuli on recognition. Our findings show that the visual span for faces is smaller than that for letters. Surprisingly, however, when differences in first-stage processing for letters and faces are accounted for, the two visual spans become nearly identical. These results suggest that the concept of visual span may describe a common sensory bottleneck that underlies different types of pattern recognition.