Positive display polarity is advantageous for both younger and older adults

Comparison of two pupillometric measures as indicators of cognitive strain and under the influence of screen luminance

The pupil diameter has been shown to provide insight to a person's experienced cognitive strain. Pupillary light responses, however, make this measure unreliable in uncontrolled settings. Two derived indicators-Index of Cognitive Activity (ICA) and Index of Pupillary Activity (IPA)-aim to 'eliminate' lighting influences, changing based only on the perceived cognitive strain. The IPA potentially offers a valuable alternative to the ICA through its fully transparent calculation, which lifts the restrictions to proprietary software and supported eye trackers. The measures are examined and compared based on two experimental studies; (i) as indicators of cognitive strain during mental arithmetic tasks and (ii) under different conditions of computer screen luminance. Results indicate that neither indicator differentiates between the increasing levels of cognitive strain. Differences in screen luminance are reflected in both indicators, although differently between the conditions. Both results contradict the claims of the indicators and further investigations are thus required.

Effects of background colour, polarity, and saturation on digital icon status recognition and visual search performance

Visual design form is an important factor affecting users' cognition of icons, which plays an important role in visual search and the perception of the status shown by icons. In the graphical user interface, the icon colour is regularly used to indicate the running state of a function. The aim of this study was to investigate the effects of icon colour features on user perception and visual search performance under different background colours. There were three independent variables in the study, including background colour (white and black), icon polarity (positive and negative), and icon saturation (60, 80, and 100%). Thirty-one participants were recruited for the experiment. Task performance and eye movement results indicated that white background as well as positive polarity and 80% saturation icons brought the best performances. The findings of this study provide useful guidelines for designing more efficient and user-friendly icons and interfaces in the future.Practitioner summary: This study was to investigate the effects of icon colour features (polarity and saturation) on user perception and visual search performance under different colour backgrounds. Task performance and eye movement results indicated that white background as well as positive polarity and 80% saturation icons brought the best performances.

Dark mode vogue: Do light-on-dark displays have measurable benefits to users?

This work investigates the effect of display polarity on cognitive load, using eye-tracking and subjective measures, and emotional reactions to assess whether the popularity of negative polarity displays is related to affective qualities or true physiological benefits. Younger and older adults tested positive and negative polarities under bright and dim environments for writing and search tasks. Eye-tracking results showed higher cognitive load using negative polarity, reflected in increased search time and pupil diameter for older adults in a bright environment and younger adults in a dim environment. For older adults, mental effort scores were higher using negative polarity for the search task in a bright environment. This group reported more positive emotions using positive polarity, while younger adults expressed more interest in negative polarity. These results suggest that older adults use positive polarity to avoid mental fatigue, while younger adults use negative polarity in a dim environment for aesthetic reasons. Practitioner summary: The effects of negative polarity on cognitive load and users' preferences are often unclear. Eye-tracking and subjective data reveals that negative polarity displays elicit higher cognitive load for older adults in a bright environment and younger adults in a dim environment, suggesting older adults prioritise reduced fatigue while younger adults prioritise the feel of the interface.

Effect of Contrast Polarity Towards Eye Fixation Rates When Reading On Smartphone

This study is conducted to investigate the effect of contrast polarity towards eye fixation patterns when reading text on a smartphone in bright and dark conditions involving the effects when reading on a smartphone such as in real-life situations. The number of fixations and duration of fixation showed no statistically significant difference (p=0.160 and 0.099 respectively). However, emmetropic subjects showed a higher result in bright conditions compared to myopic subjects (p=0.046). This concludes that emmetropic eye movement efficiency seems superior, possibly due to lower spherical order aberration as pupil size decreases in bright illumination.

Age-related normal limits for spatial vision

PURPOSE

To establish age-related, normal limits of monocular and binocular spatial vision under photopic and mesopic conditions.

METHODS

Photopic and mesopic visual acuity (VA) and contrast thresholds (CTs) were measured with both positive and negative contrast optotypes under binocular and monocular viewing conditions using the Acuity-Plus (AP) test. The experiments were carried out on participants (age range from 10 to 86 years), who met pre-established, normal sight criteria. Mean and ± 2.5σ limits were calculated within each 5-year subgroup. A biologically meaningful model was then fitted to predict mean values and upper and lower threshold limits for VA and CT as a function of age. The best-fit model parameters describe normal aging of spatial vision for each of the 16 experimental conditions investigated.

RESULTS

Out of the 382 participants recruited for this study, 285 participants passed the selection criteria for normal aging. Log transforms were applied to ensure approximate normal distributions. Outliers were also removed for each of the 16 stimulus conditions investigated based on the ±2.5σ limit criterion. VA, CTs and the overall variability were found to be age-invariant up to ~50 years in the photopic condition. A lower, age-invariant limit of ~30 years was more appropriate for the mesopic range with a gradual, but accelerating increase in both mean thresholds and intersubject variability above this age. Binocular thresholds were smaller and much less variable when compared to the thresholds measured in either eye. Results with negative contrast optotypes were significantly better than the corresponding results measured with positive contrast (p < 0.004).

CONCLUSIONS

This project has established the expected age limits of spatial vision for monocular and binocular viewing under photopic and high mesopic lighting with both positive and negative contrast optotypes using a single test, which can be implemented either in the clinic or in an occupational setting.

The influence of brightness combinations and background colour on legibility and subjective preference under negative polarity

This study explores the influence of colour combinations on legibility and aesthetic feelings for the currently popular negative polarity interface design. Legibility was measured in two different ways in two tasks: time threshold (Task I) and a 9-point subjective rating (Task II). In Task I, we combined an adaptive program to measure 37 participants' recognition thresholds and online pseudo-word recognition tasks; in Task II, 44 participants' subjective preferences were measured using a scale. We found that higher brightness contrasts led to better legibility; different background colours with identical brightness and saturation did not cause significant differences; brighter texts produced better subjective preference for aesthetic appearance, legibility, and visual comfort; and different background colours had no significant effect on subjective preference. These findings have implications for digital interface design. Practitioner summary: In display design under negative polarity, experimental results show that higher brightness contrast leads to higher legibility, while background colour has no such significant effect; background brightness and hue have no significant effect on subjective preference, but text brightness and background colour have significant interaction effect on subjective preference. Abbreviations: OLED: organic light-emitting diode; LCD: liquid crystal display; ANOVA: analysis of variance; VDT: visual displsy terminal; CET-4: college english test band 4; ISO: International Organization for Standardization; HSB: hues saturation brightness.

Curved Versus Flat Monitors: Interactive Effects of Display Curvature Radius and Display Size on Visual Search Performance and Visual Fatigue

OBJECTIVE

The aim of this study is to examine the interactive effects of display curvature radius and display size on visual search accuracy, visual search speed, and visual fatigue.

BACKGROUND

Although the advantages of curved displays have been reported, little is known about the interactive effects of display curvature radius and size.

METHOD

Twenty-seven individuals performed visual search tasks at a viewing distance of 50 cm using eight configurations involving four display curvature radii (400R, 600R, 1200R, and flat) and two display sizes (33″ and 50″). To simulate curved screens, five flat display panels were horizontally arranged with their centers concentrically repositioned following each display curvature radius.

RESULTS

For accuracy, speed, and fatigue, 33″-600R and 50″-600R provided the best or comparable-to-best results, whereas 50″-flat provided the worst results. For accuracy and fatigue, 33″-flat was the second worst. The changes in the horizontal field of view and viewing angle due to display curvature as well as the association between effective display curvature radii and empirical horopter (loci of perceived equidistance) can explain these results.

CONCLUSION

The interactive effects of display curvature radius and size were evident for visual search performance and fatigue. Beneficial effects of curved displays were maintained across 33″ and 50″, whereas increasing flat display size from 33″ to 50″ was detrimental.

APPLICATION

For visual search tasks at a viewing distance of 50 cm, 33″-600R and 50″ 600R displays are recommended, as opposed to 33″ and 50″ flat displays. Wide flat displays must be carefully considered for visual display terminal tasks.

Learning Experience Design in Health Professions Education: A Conceptual Review of Evidence for Educators

OBJECTIVES

The increasing use of online resources in emergency medicine (EM) education has driven demand for higher quality resources. Learning experience design (LED) is the study of how electronic user interfaces impact learner outcomes. We sought to summarize the evidence for LED principles to inform creation of EM educational resources.

METHODS

We performed scripted searches of MeSH terms, PubMed keywords, and hand tracings. Inclusion criteria were controlled studies using light-emitting diode or liquid crystal display monitors with Latin-based languages. Cathode ray tube (CRT) monitors were excluded because of the user experience confounders.

RESULTS

Thirty-two articles met inclusion criteria. Overall, 14-point size significantly improved legibility compared to smaller font sizes. Similarly, Verdana and Arial typefaces significantly improved legibility compared to Times New Roman typeface. Verdana also significantly decreased subjective mental workload and visibility difficulty ratings and required the least eye movement of any typefaces tested. Positive polarity (dark text on light background) significantly improved reading outcomes across many measurements over negative polarity. There was higher character identification accuracy with higher luminance. Text effects (e.g., italics), interword and interletter spacing, and page presentation are among variables with mixed or minimal evidence.

CONCLUSION

Learning experience design principles significantly impacted reading and learning outcomes in laboratory settings. No studies evaluated classroom outcomes. Recommendations for electronic learning environments are 14-point font with Verdana or Arial typeface with positive polarity (dark letters on light background). We recommend increasing screen brightness slightly. EM educators may significantly improve the speed and accuracy of learning written material by espousing evidence-based LED principles.

The Effects of Ambient Illumination, Color Combination, Sign Height, and Observation Angle on the Legibility of Wayfinding Signs in Metro Stations

Well-designed wayfinding signs play an important role in improving the service level of metro stations, ensuring the safety of passengers in evacuation, and promoting the sustainable development of public transport. This study explored the effects of ambient illumination, color combination, sign height, and observation angle on wayfinding signs’ legibility in metro stations. In the experiment, simulated metro-wayfinding signs were made to test legibility. As designed, the legibility was measured based on the following independent variables: two levels of ambient illumination (70 lux and 273 lux), two target/background color combinations (achromatic-white target on black background, chromatic-yellow target on black background), two sign heights (1.5 m and 2 m), and three observation angles (0°, 45°, 70°). The results showed that brighter ambient illumination provided passengers with higher legibility. Achromatic color combination was more legible than chromatic color combination, but not significantly. Different types of signs, set at different height, did not directly affect legibility. Observation angle had significant effects on legibility. Visibility catchment area of wayfinding signs was like an ellipse, with its short axis nearly equal to the legibility distance of the sign at 0 degrees. The findings will facilitate the layout and setting location of wayfinding signs in metro stations and improve the level of wayfinding service.

Detection of emergent large vessel occlusion stroke with CT angiography is high across all levels of radiology training and grayscale viewing methods

OBJECTIVES

CT angiography (CTA) is essential in acute stroke to detect emergent large vessel occlusions (ELVO) and must be interpreted by radiologists with and without subspecialized training. Additionally, grayscale inversion has been suggested to improve diagnostic accuracy in other radiology applications. This study examines diagnostic performance in ELVO detection between neuroradiologists, non-neuroradiologists, and radiology residents using standard and grayscale inversion viewing methods.

METHODS

A random, counterbalanced experimental design was used, where 18 radiologists with varying experiences interpreted the same patient images with and without grayscale inversion. Confirmed positive and negative ELVO cases were randomly ordered using a balanced design. Sensitivity, specificity, positive and negative predictive values as well as confidence, subjective assessment of image quality, time to ELVO detection, and overall interpretation time were examined between grayscale inversion (on/off) by experience level using generalized mixed modeling assuming a binary, negative binomial, and binomial distributions, respectively.

RESULTS

All groups of radiologists had high sensitivity and specificity for ELVO detection (all > .94). Neuroradiologists were faster than non-neuroradiologists and residents in interpretation time, with a mean of 47 s to detect ELVO, as compared with 59 and 74 s, respectively. Residents were subjectively less confident than attending physicians. With respect to grayscale inversion, no differences were observed between groups with grayscale inversion vs. standard viewing for diagnostic performance (p = 0.30), detection time (p = .45), overall interpretation time (p = .97), and confidence (p = .20).

CONCLUSIONS

Diagnostic performance in ELVO detection with CTA was high across all levels of radiologist training level. Grayscale inversion offered no significant detection advantage.

KEY POINTS

• Stroke is an acute vascular syndrome that requires acute vascular imaging. • Proximal large vessel occlusions can be identified quickly and accurately by radiologists across all training levels. • Grayscale inversion demonstrated minimal detectable benefit in the detection of proximal large vessel occlusions.

Effects of display curvature and task duration on proofreading performance, visual discomfort, visual fatigue, mental workload, and user satisfaction

This study examined the effects of display curvature and task duration on proofreading performance, visual discomfort, visual fatigue, mental workload, and user satisfaction. Five 27″ rear-screen mock-ups with distinct curvature radii (600R, 1140R, 2000R, 4000R, and flat) were used. Ten individuals per display curvature completed a series of four 15 min comparison-proofreading trials at a 600 mm viewing distance. Only proofreading speed benefited from display curvature, with 600R providing the highest mean proofreading speed. Proofreading speed increased and accuracy decreased for all display curvatures over the 1 h proofreading period. Visual discomfort, visual fatigue, and mental workload increased during the first 15 min of proofreading. A decrease in critical fusion frequency during that period indicated increases in visual fatigue and mental workload. A short break between 15 min proofreading tasks could be considered to prevent further degradation of task performance and ocular health.

Influence of contrast polarity on the accommodative response

PURPOSE

To assess the changes in the accommodative response of the eye while reading a text under different contrast polarity conditions: black letters on white background (BoW condition) and white letters on black background (WoB condition).

METHODS

Eighteen subjects with ages ranging from 21 to 41 years participated in this experimental study. The accommodative response (AR) of the eye while reading a text with BoW or WoB contrast polarity was obtained objectively with an adaptive optics system that corrected all aberrations but subject's own. Two different letter sizes (visual acuity conditions), shown on a microdisplay, were tested. The AR of each eye was measured with its natural pupil diameter at 0-3D of accommodative demand from the far point of the eye, with a step of 0.5D. The slope of the stimulus-response curve was calculated for each subject and condition.

RESULTS

The averaged maximum pupil size was bigger for reverse (WoB) than for normal (BoW) contrast with statistical significance. The slopes for the ARs of the four conditions were not significantly different from each other.

CONCLUSIONS

Contrast polarity does not seem to influence the accommodative response when reading text from an electronic microdisplay.

Mobile App Delivery of the EORTC QLQ-C30 Questionnaire to Assess Health-Related Quality of Life in Oncological Patients: Usability Study

Background

Mobile apps are evolving in the medical field. However, ongoing discussions have questioned whether such apps are really valuable and whether patients will accept their use in day-to-day clinical life. Therefore, we initiated a usability study in our department.

Objective

We present our results of the first app prototype and patient testing of health-related quality of life (HRQoL) assessment in oncological patients.

Methods

We developed an app prototype for the iOS operating system within eight months in three phases: conception, initial development, and pilot testing. For the HRQoL assessment, we chose to implement only the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30; German version 3). Usability testing was conducted for three months. Participation was voluntary and pseudonymized. After completion of the QLQ-C30 questionnaire using iPads provided by our department, we performed a short survey with 10 questions. This survey inquired about patients’ opinions regarding general aspects, including technical advances in medicine, mobile and app assistance during cancer treatment, and the app-specific functions (eg, interface and navigation).

Results

After logging into the app, the user can choose between starting a questionnaire, reviewing answers (administrators only), and logging out. The questionnaire is displayed with the same information, questions, and answers as on the original QLQ-C30 sheet. No alterations in wording were made. Usability was tested with 81 patients; median age was 55 years. The median time for completing the HRQoL questionnaire on the iPad was 4.0 minutes. Of all participants, 84% (68/81) owned a mobile device. Similarly, 84% (68/81) of participants would prefer a mobile version of the HRQoL questionnaire instead of a paper-based version. Using the app in daily life during and after cancer treatment would be supported by 83% (67/81) of participants. In the prototype version of the app, data were stored on the device; in the future, 79% (64/81) of the patients would agree to transfer data via the Internet.

Conclusions

Our usability test showed good results regarding attractiveness, operability, and understandability. Moreover, our results demonstrate a high overall acceptance of mobile apps and telemedicine in oncology. The HRQoL assessment via the app was accepted thoroughly by patients, and individuals are keen to use it in clinical routines, while data privacy and security must be ensured.

Effects of display curvature, display zone, and task duration on legibility and visual fatigue during visual search task

This study examined the effects of display curvature (400, 600, 1200 mm, and flat), display zone (5 zones), and task duration (15 and 30 min) on legibility and visual fatigue. Each participant completed two 15-min visual search task sets at each curvature setting. The 600-mm and 1200-mm settings yielded better results than the flat setting in terms of legibility and perceived visual fatigue. Relative to the corresponding centre zone, the outermost zones of the 1200-mm and flat settings showed a decrease of 8%-37% in legibility, whereas those of the flat setting showed an increase of 26%-45% in perceived visual fatigue. Across curvatures, legibility decreased by 2%-8%, whereas perceived visual fatigue increased by 22% during the second task set. The two task sets induced an increase of 102% in the eye complaint score and a decrease of 0.3 Hz in the critical fusion frequency, both of which indicated an increase in visual fatigue. In summary, a curvature of around 600 mm, central display zones, and frequent breaks are recommended to improve legibility and reduce visual fatigue.

Effects of ambient illumination, contrast polarity, and letter size on text legibility under glance-like reading

Recent research on the legibility of digital displays has demonstrated a "positive polarity advantage", in which black-on-white text configurations are more legible than their negative polarity, white-on-black counterparts. Existing research in this area suggests that the positive polarity advantage stems from the brighter illumination emitted by positive polarity displays, as opposed to the darker backgrounds of negative polarity displays. In the present study, legibility thresholds were measured under glance-like reading conditions using a lexical decision paradigm, testing two type sizes, display polarities, and ambient illuminations (near-dark and daylight-like). Results indicate that legibility thresholds, quantified as the amount of time needed to read a word accurately, were highest for the negative polarity configurations under dark ambient illumination, indicated worse performance. Conversely, the positive polarity conditions under dark ambient illumination and all conditions under bright illumination demonstrated significantly reduced thresholds, indicating greater legibility. These results are consistent with the hypothesis that the "positive polarity advantage" arises because brighter illumination produces pupillary contraction that reduces optical aberrations as light enters the eye. These results have implications for the design of automotive interfaces and other scenarios in which an interface must be optimized for glance-like reading under variations in ambient lighting conditions.

Age-related differences in the legibility of degraded text

Aging-related changes in the visual system diminish the capacity to perceive the world with the ease and fidelity younger adults are accustomed to. Among many consequences of this, older adults find that text that they could once read easily proves difficult to read, even with sufficient acuity correction. Building on previous work examining visual factors in legibility, we examine potential causes for these age-related effects in the absence of other ocular pathology. We asked participants to discriminate words from non-words in a lexical decision task. The stimuli participants viewed were either blurred or presented in a noise field to simulate, respectively, decreased sensitivity to fine detail (loss of acuity) and detuning of visually selective neurons. We then use the differences in performance between older and younger participants to suggest how older participants’ performance could be approximated to facilitate maximally usable designs.

Reading from computer screen versus reading from paper: does it still make a difference?

Four experiments were conducted to test whether recent developments in display technology would suffice to eliminate the well-known disadvantages in reading from screen as compared with paper. Proofreading speed and performance were equal for a TFT-LCD and a paper display, but there were more symptoms of eyestrain in the screen condition accompanied by a strong preference for paper (Experiment 1). These results were replicated using a longer reading duration (Experiment 2). Additional experiments were conducted to test hypotheses about the reasons for the higher amount of eyestrain associated with reading from screen. Reduced screen luminance did not change the pattern of results (Experiment 3), but positioning both displays in equal inclination angles eliminated the differences in eyestrain symptoms and increased proofreading speed in the screen condition (Experiment 4). A paper-like positioning of TFT-LCDs seems to enable unimpaired reading without evidence of increased physical strain. Practitioner Summary: Given the developments in screen technology, a re-assessment of the differences in proofreading speed and performance, well-being, and preference between computer screen and paper was conducted. State-of-the-art TFT-LCDs enable unimpaired reading, but a book-like positioning of screens seems necessary to minimise eyestrain symptoms.

Smaller pupil size and better proofreading performance with positive than with negative polarity displays

The 'positive polarity advantage' describes the fact that reading performance is better for dark text on light background (positive polarity) than for light text on dark background (negative polarity). We investigated the underlying mechanism by assessing pupil size and proofreading performance when reading positive and negative polarity texts. In particular, we tested the display luminance hypothesis which postulates that the typically greater brightness of positive compared to negative polarity displays leads to smaller pupil sizes and, hence, a sharper retinal image and better perception of detail. Indeed, pupil sizes were smaller and proofreading performance was better with positive than with negative polarity displays. The results are compatible with the hypothesis that the positive polarity advantage is an effect of display luminance. Limitations of the study are being discussed.

Positive display polarity is particularly advantageous for small character sizes: implications for display design

OBJECTIVE

To test the display luminance hypothesis of the positive polarity advantage and gain insights for display design, the joint effects of display polarity and character size were assessed with a proofreading task

BACKGROUND

Studies have shown that dark characters on light background (positive polarity) lead to better legibility than do light characters on dark background (negative polarity), presumably due to the typically higher display luminance of positive polarity presentations.

METHOD

Participants performed a proofreading task with black text on white background or white text on black background. Texts were presented in four character sizes (8, 10, 12, and 14 pt; corresponding to 0.22 degrees, 0.25 degrees, 0.31 degrees, and 0.34 degrees of vertical visual angle).

RESULTS

A positive polarity advantage was observed in proofreading performance. Importantly, the positive polarity advantage linearly increased with decreasing character size.

CONCLUSION

The findings are in line with the assumption that the typically higher luminance of positive polarity displays leads to an improved perception of detail. Application: The implications seem important for the design of text on such displays as those of computers, automotive control and entertainment systems, and smartphones that are increasingly used for the consumption of text-based media and communication. The sizes of these displays are limited, and it is tempting to use small font sizes to convey as much information as possible. Especially with small font sizes, negative polarity displays should be avoided.

Age-related changes in visual lobe shape characteristics and their relationship to visual search performance

Visual lobe shape plays an important role in visual search performance, but little is known about the age-related changes in visual lobe shape. The age-related changes in visual lobe shape characteristics and their relationships to visual search performance were investigated in this study. A total of 96 participants aged 15-64 years participated in this study. Their visual lobes were mapped on a uniform 2-D test field composed of 24 regularly spaced meridians passing through the centre of the visual field, and their search performances were also measured. The results showed that in general, age significantly affected visual lobe size, visual lobe shape and search time. As age increased, the visual lobe size decreased; in addition, the roundness, boundary smoothness, symmetry and regularity of the visual lobe deteriorated, and the search time increased. Moreover, significant correlations between visual lobe shape, search time and age were found. Regression analyses indicated that age was important in determining visual lobe shape and search time, suggesting that age differences should be considered when predicting search time and when designing tasks and products that involve visual search in our daily lives and work.

PRACTITIONER SUMMARY

Age-related changes in visual lobe shape characteristics and their relationships to visual search performance were investigated in this study. The results help to explain how tasks and products involving visual search in our daily lives and work should be designed for target audiences of different ages.