Abstract :

Past studies in English and German texts have shown that a vertical striped word (one which consists of repetitive vertical stripe components) requires a longer time to read and a longer binocular fixation time were found in the study using German texts. A biologically inspired reason related to binocular fixation has been proposed, which predicts that the prolonged reading time is caused by the additional effort from the binocular vision system to align an image with a high occurrence of vertical stripes projected on the left and right retinas. Experiments have been conducted to verify such claim. Common Chinese characters (taken from a Hong Kong Baptist University Language Center report) were analyzed into three groups: (i) character with more repetitive vertical stripes; (ii) character with less repetitive vertical stripes; and (iii) neutral, using horizontal autocorrelation as an objective measurement. The results from experiment 1 and experiment 2 have shown that a character with more repetitive vertical stripes exhibits a significantly longer recognition time than a character with less repetitive vertical stripes. In experiment 3, a character with more repetitive vertical stripes does correlates significantly to a longer binocular fixation duration. With the results from these experiments, we know that the effect of vertical stripes prolonged recognition time and binocular fixation duration of Chinese character. If the proposed reason is correct, in a monocular viewing condition the recognition time and fixation duration shall not be affected by the presence of vertical stripes, as the need of aligning images in two retinas is no longer required. To put the proposed theory under the test, experiment 4 tested the effect of character types in binocular and monocular viewing condition. As predicted by the theory, recognition time and fixation duration for character with more repetitive vertical stripes is significantly longer in binocular viewing conditions but not monocular viewing condition. The results showed that the increased in fixation duration is due to binocular vision of human and more specifically due to the vergence movement needed for the two eyes to correct the binocular disparity. With that, a fifth experiment is conducted to place a biologically inspired binocular vergence model under a series of simulation to examine how the proposed theory. The two types of Chinese characters were shown to the vergence model in a simulation, and the results indicated that the model does reached a smaller binocular disparity viewing a character with more repetitive vertical stripes. These series of experiments showed that the effect of vertical stripes is most likely related to fundamental biology of human binocular vision.