Assessing effects of fixation demands on perception of lateralized words: A visual window technique for studying hemispheric asymmetry.

A major concern when using lateralized words to study hemispheric asymmetry is that the retinal eccentricity of targets is matched across visual hemifields. The standard technique is to fixate a point fixed at the centre of the visual field. However, the demands of this fixation task are substantial and so may confound performance with lateralized targets. To investigate this possibility, words were presented unilaterally in each visual hemifield and retinal eccentricity was controlled using (a) a fixed central point or (b) a window technique that permitted small shifts in fixation while maintaining accurate retinal eccentricity by using automatic adjustments to target location. Fixation errors and time to fixate indicated that the demands of the standard technique were considerable and far greater than those of the window technique. Nevertheless, both techniques produced the same pattern of visual field effects, indicating that the demands of fixating a fixed central point do not confound performance with lateralized words. However, the window technique was more efficient and easier for participants to use and so offers a new improved methodology for studying hemispheric asymmetry.