Abstract
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.
Highlights
Reading is indispensable to many daily activities, affecting a person’s ability to function at work and at home[1], and is a major component of vision-related quality of life[2]
The crowding effect was quantified as crowding zone[11, 13, 25, 40, 63]
We measured the visual span because it is known to be highly correlated with reading speed[64, 67, 71,72,73] while being largely limited by crowding[21, 66,67,68,69]
Summary
Reading is indispensable to many daily activities, affecting a person’s ability to function at work and at home[1], and is a major component of vision-related quality of life[2]. Among many accounts of crowding[24,25,26,27,28,29,30], a popular explanation is that features of the target and flankers are integrated inappropriately due to a larger integration zone (or perceptive pooling zone)[20, 31,32,33,34,35,36,37,38,39], which results in relevant features being perceptually indistinguishable Consistent with this view, crowding grows with increasing retinal eccentricity as receptive field size increases in the periphery (i.e., scale shift)[11, 40, 41]. The findings of these studies suggested the susceptibility of older adults to crowded visual environments While these findings together hint at a possible role of crowding in age-related decline in reading, this question still remains to be answered. We compared differences in reading speed, crowding zone, and the size of the visual span between the two age groups and examined the relationship between crowding (i.e., crowding zone and the visual span) and reading speed
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