Perceptual span asymmetry reconsidered: The case of Japanese.

The Japanese writing system combines visually intricate logographic kanji with simpler phonographic kana. Moreover, Japanese is a subject-object-verb (SOV), head-final language with flexible word order, which often increases structural complexity and imposes additional cognitive demands during sentence processing. Despite these unique features, the spatial limit of visual processing in Japanese has not been thoroughly investigated. To identify the perceptual span, the present study employed a gaze-contingent moving window paradigm to measure the amount of information acquired per fixation in two experiments. The results showed that reading speed and fixation duration resembled those in the control condition, with no viewing constraint applied, when the window revealed five characters to the left and six to the right of fixation. The perceptual span in Japanese falls between those of English and Chinese, supporting the notion that the visual density of a writing system affects perceptual span. Notably, the perceptual span in Japanese appears more symmetrical than in other writing systems. These findings offer insights into visual processing mechanisms during reading.