Reading direction and the central perceptual span: evidence from Arabic and English.

In English and other alphabetic languages read from left to right, useful information acquired during each fixational pause is generally reported to extend much further to the right of each fixation than to the left. However, the asymmetry of the perceptual span for alphabetic languages read in the opposite direction (i.e., from right to left) has received very little attention in empirical research. Accordingly, we investigated the perceptual span for Arabic, which is one of the world's most widely read languages and is read from right to left, using a gaze-contingent window paradigm in which a region of text was displayed normally around each point of fixation, while text outside this region was obscured. Skilled Arabic readers who were bilingual in Arabic and English read Arabic and English sentences while a window of normal text extended symmetrically 0.5(o) to the left and right of fixation or asymmetrically, by increasing this window to 1.5(o) or 2.5(o) to either the left or the right. When English was read, performance across window conditions was superior when windows extended rightward. However, when Arabic was read, performance was superior when windows extended leftward and was essentially the reverse of that observed for English. These findings show for the first time that a leftward asymmetry in the central perceptual span occurs when Arabic is read and, for the first time in over 30 years, provide a new indication that the perceptual span for alphabetic languages is modified by the overall direction of reading.