Liu L, Arditi A
Arlene R. Gordon Research Institute of Lighthouse International, 111 East 59th Street, New York, NY 10022-1202, USA.
Vision Res. 2000;40(9):1059-67. doi: 10.1016/s0042-6989(99)00247-3.
In our previous studies of the crowding effect, we have observed that human observers tend to underestimate the length of a letter string (the number of letters in the string) when the letters are close to visual acuity, and the interletter spacings are small. In this study, we asked our observers to identify letters in randomly presented four-letter and five-letter strings. We found that, when a priori knowledge of the lengths of letter strings was not available, the probability of underestimating string length increased with decreasing interletter spacing. The causes of underestimation errors appeared to be the omission of an interior letter and the merging of two neighboring letters. Since our experiments were conducted in the foveal region, neither spatial uncertainty nor split attention can explain the underestimation errors. The effect of the point spread function of the eye on closely packed letter strings is discussed.
在我们之前关于拥挤效应的研究中，我们观察到当字母接近视敏度且字母间距较小时，人类观察者往往会低估字母串的长度（字符串中的字母数量）。在本研究中，我们要求观察者识别随机呈现的四个字母和五个字母的字符串中的字母。我们发现，当无法获得字母串长度的先验知识时，低估字符串长度的概率会随着字母间距的减小而增加。低估误差的原因似乎是遗漏了一个内部字母以及两个相邻字母的合并。由于我们的实验是在中央凹区域进行的，空间不确定性和注意力分散都无法解释这些低估误差。本文讨论了眼睛的点扩散函数对紧密排列字母串的影响。
