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.

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.

Differential coactivation in a redundant signals task with weak and strong go/no-go stimuli.

When participants respond to stimuli of two sources, response times (RTs) are often faster when both stimuli are presented together relative to the RTs obtained when presented separately (redundant signals effect [RSE]). Race models and coactivation models can explain the RSE. In race models, separate channels process the two stimulus components, and the faster processing time determines the overall RT. In audiovisual experiments, the RSE is often higher than predicted by race models, and coactivation models have been proposed that assume integrated processing of the two stimuli. Where does coactivation occur? We implemented a go/no-go task with randomly intermixed weak and strong auditory, visual, and audiovisual stimuli. In one experimental session, participants had to respond to strong stimuli and withhold their response to weak stimuli. In the other session, these roles were reversed. Interestingly, coactivation was only observed in the experimental session in which participants had to respond to strong stimuli. If weak stimuli served as targets, results were widely consistent with the race model prediction. The pattern of results contradicts the inverse effectiveness law. We present two models that explain the result in terms of absolute and relative thresholds.

A tutorial on testing the race model inequality.

When participants respond in the same way to stimuli of two categories, responses are often observed to be faster when both stimuli are presented together (redundant signals) relative to the response time obtained when they are presented separately. This effect is known as the redundant signals effect. Several models have been proposed to explain this effect, including race models and coactivation models of information processing. In race models, the two stimulus components are processed in separate channels, and the faster channel determines the processing time. This mechanism leads, on average, to faster responses to redundant signals. In contrast, coactivation models assume integrated processing of the combined stimuli. To distinguish between these two accounts, Miller (Cognitive Psychology, 14, 247-279, 1982) derived the well-known race model inequality, which has become a routine test for behavioral data in experiments with redundant signals. In this tutorial, we review the basic properties of redundant signals experiments and current statistical procedures used to test the race model inequality during the period between 2011 and 2014. We highlight and discuss several issues concerning study design and the test of the race model inequality, such as inappropriate control of Type I error, insufficient statistical power, wrong treatment of omitted responses or anticipations, and the interpretation of violations of the race model inequality. We make detailed recommendations on the design of redundant signals experiments and on the statistical analysis of redundancy gains. We describe a number of coactivation models that may be considered when the race model has been shown to fail.

Influence of auditory and audiovisual stimuli on the right-left prevalence effect.

When auditory stimuli are used in two-dimensional spatial compatibility tasks, where the stimulus and response configurations vary along the horizontal and vertical dimensions simultaneously, a right-left prevalence effect occurs in which horizontal compatibility dominates over vertical compatibility. The right-left prevalence effects obtained with auditory stimuli are typically larger than that obtained with visual stimuli even though less attention should be demanded from the horizontal dimension in auditory processing. In the present study, we examined whether auditory or visual dominance occurs when the two-dimensional stimuli are audiovisual, as well as whether there will be cross-modal facilitation of response selection for the horizontal and vertical dimensions. We also examined whether there is an additional benefit of adding a pitch dimension to the auditory stimulus to facilitate vertical coding through use of the spatial-musical association of response codes (SMARC) effect, where pitch is coded in terms of height in space. In Experiment 1, we found a larger right-left prevalence effect for unimodal auditory than visual stimuli. Neutral, non-pitch coded, audiovisual stimuli did not result in cross-modal facilitation, but did show evidence of visual dominance. The right-left prevalence effect was eliminated in the presence of SMARC audiovisual stimuli, but the effect influenced horizontal rather than vertical coding. Experiment 2 showed that the influence of the pitch dimension was not in terms of influencing response selection on a trial-to-trial basis, but in terms of altering the salience of the task environment. Taken together, these findings indicate that in the absence of salient vertical cues, auditory and audiovisual stimuli tend to be coded along the horizontal dimension and vision tends to dominate audition in this two-dimensional spatial stimulus-response task.

Shared spatial representations for physical locations and location words in bilinguals' primary language.

For monolinguals, the Simon effect is eliminated when Simon task trials are intermixed with ones in which participants respond to the words left and right with incompatibly mapped keypresses. For bilingual Dutch/French speakers, this result has been shown to occur when the words are in Dutch (their first and primary language), but not when they are in French. To dissociate the influence of order in which the languages were learned from whether the language was the primary one currently being used, we tested bilinguals who learned Spanish or Vietnamese as their first language but for whom English became their primary language. For both groups, the incompatible location-word mapping influenced performance of the Simon task when the words were in English but not when they were in the first language. These findings indicate that the strength of language, not order of acquisition, is the critical factor.