Abstract
Reading is a demanding task, and while many studies have investigated the visual factors associated with reading, the recent development of variable fonts opens new avenues for this research. Variable fonts can be customized along a set of continuous parametric axes within a single font file (e.g., thin stroke, slant, etc.), lending themselves readily to psychophysical techniques. To understand how these settings can influence individual reading performance and which settings may improve reading efficiency, we recorded participants’ eye movements as they read short passages. For this study, we varied five font parameters within Roboto Flex: thick stroke, thin stroke, slant, weight, and width at five levels each. Participants read one passage per setting, displayed across four screens, and we measured saccade amplitude normalized to letter width as well as the number and duration of fixations. Our results demonstrate that increasing width and weight decrease reading efficiency since saccade amplitude decreased as letters became wider and visually heavier. Increasing thick stroke had the largest effect on reading efficiency, while thin stroke and slant had the smallest. We also found considerable individual variability in the degree to which these axes impacted individuals’ reading efficiency and the number of fixations they made. Our results suggest that the customizability of variable fonts and the sensitivity of our gaze measures may make it possible to quickly find the settings that are best for each reader and enable a new range of psychophysical investigations of the impact of font on reading.