Evaluating hemispheric divisions in processing fixated words: the evidence from Arabic

Abstract

Some studies have claimed that, when fixating a word, a precise split in foveal processing produces substantial effects on word recognition because all letters to the left and right of fixation project to different, contralateral hemispheres. Recently in this Journal, Jordan, Paterson, Kurtev, and Xu (2010, Cortex, 46, 298-309) evaluated this claim using precisely-controlled procedures of fixation and stimulus presentation and found no evidence of split-foveal processing. However, in line with other research in this area, these findings were obtained using a Latinate alphabetic language (in this case English) which may induce specific effects on performance. Consequently, here we report a further study which used stimuli from a fundamentally different, non-Latinate alphabetic language (Arabic) with characteristics better suited to revealing effects of split-foveal processing, if they exist. Participants made lexical decisions to five-letter Arabic words (and nonwords) when fixations were made immediately to the right (location 1) or left (location 6) of each stimulus, or at one of the four possible inter-letter locations (locations 2-5). Fixation location was carefully controlled using an eye-tracker linked to a fixation-contingent display and all stimuli were presented within foveal vision to avoid confounding influences of extrafoveal projections. Performance was equally poorest when fixating locations 1 and 6 (i.e., when words were shown entirely to either the left or right of fixation), equally intermediate for locations 2 and 5, and equally superior for locations 3 and 4 (i.e., the centre of words). Moreover, additional, word-specific analyses showed no evidence of the effects of fixation location on individual word recognition also predicted by split-foveal processing. These findings from a non-Latinate language complement those reported previously for English to provide further evidence that while fixation location influences word recognition, these influences occur with no functional division in hemispheric processing at the point of fixation.