Font size modulates saccade-target selection in Chinese reading

In alphabetic writing systems, saccade amplitude (a close correlate of reading speed) is independent of font size, presumably because an increase in the angular size of letters is compensated for by a decrease of visual acuity with eccentricity. We propose that this invariance may (also) be due to the presence of spaces between words, guiding the eyes across a large range of font sizes. Here, we test whether saccade amplitude is also invariant against manipulations of font size during reading Chinese, a character-based writing system without spaces as explicit word boundaries for saccade-target selection. In contrast to word-spaced alphabetic writing systems, saccade amplitude decreased significantly with increased font size, leading to an increase in the number of fixations at the beginning of words and in the number of refixations. These results are consistent with a model which assumes that word beginning (rather than word center) is the default saccade target if the length of the parafoveal word is not available.