Reading saccades that occur within a single line of text are guided by the size of letters.However, readers occasionally need to make longer saccades (known as return-sweeps) that take their eyes from the end of one line of text to the beginning of the next. In this study, we tested whether return-sweep saccades are also guided by font size information and whether this guidance depends on visual acuity constraints. To do this, we manipulated the font size of letters (0.29 vs 0.39º per character) and the length of the first line of text (16 vs 26º). The larger font resulted in return-sweeps that landed further to the right of the line start and in a reduction of corrective saccades compared to the smaller font. This suggests that font size information is used when programming return-sweeps and corrective saccades. Returnsweeps in the longer line condition landed further to the right of the line start and the proportion of corrective saccades increased compared to the short line condition. This likely reflects an increase in saccadic range error with the increase in saccade size. Critically, however, there was no interaction between font size and line length. This suggests that when programming return-sweeps, the use of font size information does not depend on visual acuity at the saccade target. Instead, it appears that readers rely on global typographic properties of the text in order to maintain an optimal number of characters to the left of their first fixation on a new line.

Recent research on return-sweep saccades has improved our understanding of eye movements when reading paragraphs. However, these saccades, which take our gaze from the end of one line to the start of the next line, have been studied only within the context of silent reading. Articulatory demands and the coordination of the eye–voice span (EVS) at line boundaries suggest that the execution of this saccade may be different in oral reading. We compared launch and landing positions of return-sweeps, corrective saccade probability and fixations adjacent to return-sweeps in skilled adult readers while reading paragraphs aloud and silently. Compared to silent reading, return-sweeps were launched from closer to the end of the line and landed closer to the start of the next line when reading aloud. The probability of making a corrective saccade was higher for oral reading than silent reading. These indicate that oral reading may compel readers to rely more on foveal processing at the expense of parafoveal processing. We found an interaction between reading modality and fixation type on fixation durations. The reading modality effect (i.e., increased fixation durations in oral compared to silent reading) was greater for accurate line-initial fixations and marginally greater for line-final fixations compared to intra-line fixations. This suggests that readers may use the fixations adjacent to return-sweeps as natural pause locations to modulate the EVS.

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