关键词: 空格, 汉语阅读, 老化, 视觉拥挤, 眼动

Abstract: We report an experiment that investigated effects of changes in inter-character spacing on the eye movements of young (18-35 years) and older (65+ years) Chinese readers. Compared to young adults, older adults experience greater reading difficulty due to visual and cognitive declines in older age (Rayner et al., 2006). In particular, older adults appear to suffer more from effects of visual crowding, which is increased difficulty recognizing an object when closely surrounded by visually similar objects (McCarley et al., 2012). Numerous studies suggest increased text spacing can offset visual crowding, and therefore benefit readers who are vulnerable to its effects, such as children with developmental dyslexia (Zorzi et al., 2012). However, research has not investigated if similar benefits are observed for older readers. Accordingly, we investigated this issue. Moreover, we specifically investigated the issue in Chinese as research also suggests that crowding effects vary depending on the visual complexity of Chinese characters (Wang H, et al., 2014). To do so, we conducted an eye movement experiment with skilled young and older adult readers. The design of the experiment was 2(age: older adult , young adult)×3 (character spacing: decreased spacing, normal spacing, increased spacing)mixed, with the between-participants factor age group (young adult, older adult) and within-participants factor character spacing(decreased ,normal ,increased). An EyeLink 2000 eye-tracker recorded each participant’s right-eye gaze location every millisecond during binocular viewing. Stimuli were 48 sentences that all contained three inter-character spacing. Participants read sentences composed mostly of complex (number of strokes > 9) characters, presented either with normal inter-character spacing or increased (3pt) or decreased (3pt) inter-character spacing. Typical patterns of age-related reading difficulty were observed. Compared to young adults, older adults read more slowly, had longer sentences reading times, more and longer fixations, more regressions and shorter forward saccades. Inter-character spacing also had influences, compared to normal spacing, decreased spacing produced longer average fixation durations, less fixation counts and shorter forward saccade length; increased spacing produced shorter average fixation durations, more fixation counts and longer forward saccade length. In addition, significant interactions between age-group and spacing condition were found for average fixation durations, forward saccade length and number of forward saccade fixations which were due to reading processes were disrupted more for the older than younger adults when spacing was decreased than increased. Crucially, however, these effects did not differ across age groups, indicating that older readers did not benefit more from increased letter spacing. We discuss these findings in relation to other findings showing an advantage of increasing text spacing for participant groups who are vulnerable to visual crowding.

Key words: spacing, Chinese reading, Aging, visual crowing, eye movements