Department of Psychology, Neuroscience, and Behavior, McMaster University, Hamilton, Ont., Canada.
J Exp Child Psychol. 2010 Dec;107(4):423-37. doi: 10.1016/j.jecp.2010.05.009. Epub 2010 Jul 14.
Crowding refers to impaired target recognition caused by surrounding contours. We investigated the development of crowding in central vision by comparing single-letter and crowding thresholds in groups of 5-year-olds, 8-year-olds, 11-year-olds, and adults. The task was to discriminate the orientation of a Sloan letter E. Single-letter thresholds, defined as the stroke width forming the smallest discriminable E, were worse than those of adults (0.83 arcmin) at 5 years of age (1.05 arcmin) but not at older ages (8-year-olds: 0.81 arcmin; 11-year-olds: 0.78 arcmin). The maximum distances over which crowding occurred, as measured in multiples of threshold stroke width, were smaller in adults (2.83) than in the three groups of children, who did not differ from each other (5-year-olds: 7.03; 8-year-olds: 7.84; 11-year-olds: 7.13). Thus, even 11-year-olds are more affected than adults by surrounding contours despite having single-letter acuity that has been mature for several years. The stronger influence of crowding in children may be caused by immaturities in the brain areas beyond the primary visual cortex (V1) where early visual inputs are combined and may contribute to their slower reading speed.
拥挤是指由于周围轮廓而导致目标识别受损。我们通过比较 5 岁、8 岁、11 岁和成年组的单个字母和拥挤阈值，研究了中央视觉拥挤的发展。任务是辨别 Sloan 字母 E 的方向。单个字母阈值定义为形成最小可分辨 E 的笔画宽度，在 5 岁时比成年人（0.83 弧分）差（1.05 弧分），但在年龄较大时不差（8 岁：0.81 弧分；11 岁：0.78 弧分）。以阈值笔画宽度的倍数测量的拥挤发生的最大距离，成年人（2.83）比三组儿童小，儿童之间没有差异（5 岁：7.03；8 岁：7.84；11 岁：7.13）。因此，即使是 11 岁的孩子也比成年人更容易受到周围轮廓的影响，尽管他们的单个字母视力已经成熟了好几年。在 V1 之外的大脑区域，拥挤的影响更强，可能是由于这些区域不成熟，而早期视觉输入在这些区域中进行了组合，这可能导致他们的阅读速度较慢。
