Linking crowding, visual span, and reading

Abstract

The visual span is hypothesized to be a sensory bottleneck on reading speed with crowding thought to be the major sensory factor limiting the size of the visual span. This proposed linkage between crowding, visual span, and reading speed is challenged by the finding that training to read crowded letters reduced crowding but did not improve reading speed (Chung, 2007). Here, we examined two properties of letter-recognition training that may influence the transfer to improved reading: the spatial arrangement of training stimuli and the presence of flankers. Three groups of nine young adults were trained with different configurations of letter stimuli at 10° in the lower visual field: a flanked-local group (flanked letters localized at one position), a flanked-distributed group (flanked letters distributed across different horizontal locations), and an isolated-distributed group (isolated and distributed letters). We found that distributed training, but not the presence of flankers, appears to be necessary for the training benefit to transfer to increased reading speed. Localized training may have biased attention to one specific, small area in the visual field, thereby failing to improve reading. We conclude that the visual span represents a sensory bottleneck on reading, but there may also be an attentional bottleneck. Reducing the impact of crowding can enlarge the visual span and can potentially facilitate reading, but not when adverse attentional bias is present. Our results clarify the association between crowding, visual span, and reading.

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

“…The first concerns the precise nature of the effects we observed. Other research that has used the trigram task attributes visual span effects primarily to crowding rather than other perceptual factors ([49]; see also [34,64]); and in the study by Liu et al [46], the aging effects they observed seemed principally to be due to increased crowding rather than reduced acuity. The age difference in span size for high complexity characters in the present study may also reflect a larger crowding effect for older adults.…”

“…Another approach which is argued to provide a clearer indication of specifically perceptual limitations on the acquisition of linguistic information has used a non-reading task (the trigram task) to estimate the number of letters that can be recognized reliably on each glance without moving the eyes (the visual span; see [31,34,35,36,37,38,39]). In this, trigrams (that do not form a word) are displayed briefly at either a central point or locations to its left and right on each trial in an experiment.…”

“…A further concern for the present research was to ensure that task performance by the young and older adults was not affected by fixation inaccuracy. The vast majority of research using the trigram task has relied on instructions to emphasize the importance of fixating a central point prior to stimulus presentation, sometimes supplemented by visual inspection (via a camera) to exclude trials in which participants make anticipatory eye movements (e.g., [34,36,46,49]; but see [37], for a study that used an eye-tracker to ensure fixation accuracy). Substantial evidence indicates instructions alone are insufficient to ensure fixation accuracy in experiments, and that fixation inaccuracy can adversely affect performance in studies assessing the recognition of linguistic stimuli presented each side of a designated fixation location ([51,52]; see also [53,54]).…”

Aging Effects on the Visual Span for Alphabetic Stimuli

“…The visual span, which focuses on sensory bottom-up constraints on reading, may provide a clearer indication of specifically perceptual limitations on the acquisition of linguistic information. In this paradigm, a non-reading task (the trigram task) is used to estimate the number of letters that can be recognized reliably on each glance without moving the eyes (see Frey & Bosse, 2018;He & Legge, 2017;Legge et al, 1997;Legge, Cheung, Yu, Chung, Lee, & Owens, 2007;Legge, Mansfield, & Chung, 2001;O'Regan, 1990;.…”

Korean reading speed: Effects of print size and retinal eccentricity

“…Identifying a Korean character involves identifying different crowded symbols with an inter-symbol spacing that is even smaller than the character spacing. Since crowding poses a major sensory limitation on reading (He & Legge, 2017; He, Legge, & Yu, 2013; Pelli et al, 2007), Korean reading, which is limited by both within-and between-character crowding, may exhibit different characteristics compared to English reading, which is limited mainly by between-character crowding. In our study, we compared Korean and English reading performance in central and peripheral vision.…”