Abstract: Perceptual span refers to the area of effective vision from which useful information can be obtained during a fixation in reading (McConkie and Rayner, 1975; Rayner and Pollatsek, 1989;D. Shen et al.,2008). Research has demonstrated that skilled adult readers of Chinese obtain useful information from an asymmetric region extending roughly 1 character spaces to the left of fixation to about 2~3 character spaces to the right of fixation. To determine the size of the perceptual span, the classic gaze-contingent moving-window technique was developed (McConkie and Rayner, 1975 ). In this technique, the text outside a pre-defined window around the point of fixation is masked by Xs or scrambled letters. Thus, wherever the reader looks, the text is visible within the window, but outside the window the text is disrupted in some way. By varying the masking material, the researcher have found the perceptual span is different in English and other alphabetic writing systems. In the present study gaze-contingent moving-window technique was used to explore the development of perceptual span in Chinese reading. 24 third graders, 24 fifth graders and 24 college students participated in the experiment. Their eye movements were recorded with a SR Research EyeLink 2K eye tracker. 120 sentences were presented in six viewing conditions (R0, L1R1,L2R2, L3R3, L4R4 and whole line) to examine the perceptual span of participants in different conditions. The results showed: (1)Ages, material difficulties and reading skill affected perceptual span independently. (2) The third graders could obtain useful information from a region about 1~2 character spaces to the right of fixation, and the perceptual span of the fifth graders and adults was about 2~3 character spaces to the right of fixation. (3) Compared with easy materials, the reading efficiency of reading difficult materials was lower, average fixation time was longer, perceptual span and forward saccade amplitude was smaller. (4)perceptual span of higher readers was larger than that of slower readers, especially in reading easy materials.In summary, the perceptual span is affected by age, difficulty of materials and reading ability. The perceptual span of reading is larger with the development of age and reading ability, and the readers can get larger perceptual span of easy material than difficult ones.

Key words: Chinese reading, perceptual span, gaze-contingent moving-window technique, eye movement