Tracking the Effects of Eccentricity on the Integration of Orthographic Information From Multiple Words

In adult readers, the perceptual span is approximately 14-15 characters to the right of the fixated word, corresponding to approximately 5° of visual angle. However, the extent of information processing within this area remains unclear. In the present study, we address this question using a novel adaptation of the flankers task in which the eccentricity of the flankers with respect to the central target word is increased. Fifty-four participants performed a lexical decision task on a central four-letter word flanked by two words of equal length. The flankers were either orthographically related (rock - rock) or unrelated (path - rock) to the target, and their eccentricity varied from 1.65° to 4.29° (center-to-center) in 0.33° steps. Participants' fixation was controlled by an eye-tracker using the fixation point as a trigger, and stimuli were displayed for 170 ms to avoid any eye movement. Results showed that the effect of unrelated flankers decreased with increasing eccentricity, while there was no effect of eccentricity of related flankers. In particular, the unrelated flankers affected central word processing up to the end of the parafovea. This observation provides evidence that the outer limits of the parafovea are engaged beyond prelexical processing. Lexical frequency influenced the magnitude of both reaction times (RTs) and accuracy rates, but did not interact with any variables. This novel adaptation of the flankers task has potential advantages for investigating the spatial integration of orthographic information across the perceptual span.