The effect of serifs and stroke contrast on low vision reading.

PURPOSE: Patients with low vision are generally recommended to use the same fonts as individuals with normal vision. However, we are yet to fully understand whether stroke width and serifs (small ornamentations at stroke endings) can increase readability. This study's purpose was to characterize the interaction between two factors (end-of-stroke and stroke width) in a well-defined and homogenous group of patients with low vision. METHODS: Font legibility was assessed by measuring word identification performance of 19 patients with low vision (autosomal dominant optic atrophy [ADOA] with a best-corrected average visual acuity 20/110) and a two-interval, forced-choice task was implemented. Word stimuli were presented with four different fonts designed to isolate the stylistic features of serif and stroke width. RESULTS: Font-size threshold and sensitivity data revealed that using a single measure (i.e., font-size threshold) is insufficient for detecting significant effects but triangulation is possible when combined with signal detection theory. Specifically, low stroke contrast (smaller variation in stroke width) yielded significantly lower thresholds and higher sensitivity when a font contained serifs (331 points; d' = 1.47) relative to no serifs (345 points; d' = 1.15), E(µsans, low - µserif, low) = -14 points, 95 % Cr. I. = [-24, -5], P(δ > 0) = 0.99 and E(µserif, low - µsans, low) = 0.32, 95 % Cr. I. = [0.16, 0.49], P(δ > 0) = 0.99. CONCLUSION: In people with low visual acuity caused by ADOA, the combination of serifs and a uniform stroke width resulted in better text legibility than other combinations of uniform/variable stroke widths and presence/absence of serifs.

The dispute about sans serif versus serif fonts: An interaction between the variables of serif and stroke contrast.

AIM: It is a long-lasting dispute whether serif or sans serif fonts are more legible. However, different fonts vary on numerous visual parameters, not just serifs. We investigated whether a difference in word identification can be attributed to the presence or absence of serifs or to the contrast of the letter stroke. METHOD: Participants performed a word-recognition two-interval, forced-choice task (Exp. 1) and a classic lexical decision task (Exp. 2). In both experiments the word stimuli were set with four new fonts, which were developed to isolate the stylistic features of serif and letter-stroke contrast. Two measures (i.e., font-size threshold & sensitivity) were analysed. RESULTS: The threshold measure of both experiments yielded a single significant main effect of stroke contrast such that low stroke contrast elicited lower than high stroke contrast. The sensitivity measure of Experiment 1 yielded a single significant effect of the interaction between serifs and stroke contrast. Specifically, at the sans-serif level, low stroke contrast revealed better sensitivity, relative to high stroke contrast. At the serif level, the opposite stroke contrast pattern was observed. CONCLUSION: Sans serif fonts with low stroke contrast yield better performance and if a serif font is used, high stroke contrast yields better performance than low stroke contrast. Limitations and future directions are discussed.

Closed letter counters impair recognition.

An often-repeated piece of advice when choosing fonts for great legibility is to use fonts with large counters and apertures. To identify effects of open and closed apertures on the letters 'a', 'c', 'e', 'r', 's', 't' and 'f', we ran an experiment using the serif font Pyke as stimulus. The letters in focus were designed for this experiment with three variations of open apertures (Open, Medium and Closed). The experimental paradigm was to present a letter either with or without flankers in the parafovea at 2° eccentricity. The findings showed that participants had more trouble identifying the letter if it was set in a font variation with closed apertures.

Fonts of wider letter shapes improve letter recognition in parafovea and periphery.

Most text on modern electronic displays is set in fonts of regular letter width. Little is known about whether this is the optimal font width for letter recognition. We tested three variants of the font family Helvetica Neue (Condensed, Standard, and Extended). We ran two separate experiments at different distances and different retinal locations. In Experiment 1, the stimuli were presented in the parafovea at 2° eccentricity; in Experiment 2, the stimuli were presented in the periphery at 9° eccentricity. In both experiments, we employed a short-exposure single-report trigram paradigm in which a string of three letters was presented left or right off-centre. Participants were instructed to report the middle letter while maintaining fixation on the fixation cross. Wider fonts resulted in better recognition and fewer misreadings for neighbouring letters than narrower fonts, which demonstrated that wider letter shapes improve recognition at glance reading in the peripheral visual view. Practitioner summary: Most of the text is set in fonts of regular letter width. In two single-target trigram letter recognition experiments, we showed that wider letter shapes facilitate better recognition than narrower letter shapes. This indicates that when letter identification is a priority, it is beneficial to choose fonts of wider letter shapes.

The effect of font width on eye movements during reading.

Certain font features (e.g., letter width) can change the amount of space occupied by text in published works. Font styles/features are also known to affect reading eye movements (EM); however, few studies have examined these effects - and none used high-resolution displays. We examined the effects of font width on EMs by utilizing four fonts, from the Univers family, which varied in letter-width magnitude. Participants' (n = 25) reading speed, saccade velocity, and the duration/number of fixations and saccades were recorded. The Ultra Condensed font significantly influenced readability and yielded: fewer fixations and saccades; longer fixation durations than the Roman and Extended fonts; and shorter saccade durations, relative to the other fonts. Readers efficiently adjusted their EMs such that no reading-speed differences were observed. The eye-tracking metrics revealed two trade-off effects: (1) fewer and shorter EMs and (2) more and longer EMs, which were revealed by the font-width manipulation.

High letter stroke contrast impairs letter recognition of bold fonts.

To make graphical user interfaces look more fashionable, designers often make use of high-stroke-contrast fonts. We are yet to understand how these fonts affect reading. We examined the effect of letter-stroke contrast on three bold fonts, one with extreme contrast between thick and thin strokes, one with no contrast, and one in between. The fonts were designed for this experiment to enable control of font variables. Participants identified the middle letter in a lowercase letter trigram in each trial, briefly presented in the parafovea (at 2° left and right of fixation) and at the foveal fixation point. There was evidence for letter recognition impairment for the font with high stroke contrast compared to the fonts with low and medium stroke contrast, while there was no significant difference in performance between the medium- and low-stroke-contrast fonts. The results suggest that bold fonts with high stroke contrast should not be considered for designs where letter recognition is a priority.

Smaller visual angles show greater benefit of letter boldness than larger visual angles.

Research has shown that fonts viewed at a smaller visual angle benefit from greater letter boldness. Since small and large visual angles operate on different spatial frequencies, we examined whether the effect was dependent on font size. By applying a paradigm of single-letter exposure across two experiments, we showed that fonts of thinner letter strokes and of extreme boldness decreased recognition for all tested font sizes, and that there was a positive effect of boldness at small visual angles which did not occur at large visual angles. The paper provides evidence that bolder fonts are less effective at improving recognition at larger visual angles, and that over a scale of font weights there is a drop-off at the lightest and the heaviest extremes at all tested font sizes.