Effects of speed,motion type,and stimulus size on dynamic visual search: A study of radar human–machine interface

Human visual perception behavior in dynamic environments could be affected by the motion properties of stimuli. The purpose of this study was to investigate the effects of motion type, size, and speed of stimulus on visual search performance and visual comfort in both single- and double-target tasks. Twenty participants attended an experiment in which they finished two tasks at three speeds (low, medium, and high), in two motion types (flicker, uniform), with varied levels of stimulus size (small, medium, and large) on a display. The search time, accuracy, critical flicker frequency, visual comfort, and cognitive load were recorded to provide a comprehensive understanding of participants' visual preferences during the experiment.The results indicated the increasing speed would weaken participants performance on visual search tasks; Medium-sized stimuli were recommended considering search efficiency and cost-effectiveness; More importantly, the present study also found that flicker motion led to better task performance in the low-speed task, due to increased alertness and lead physiological arousal effects, which may imply the past studies have overstated the negative effects of flickering in dynamic environments.     

An empirical evaluation of multi-media based learning of a procedural task

The present study investigated the effects of multi-media modules and their combinations on the learning of procedural tasks. In the experiment, 72 participants were classified as having either low- or high spatial ability based on their spatial ability test. They were randomly assigned to one of the six experimental conditions in a 2 × 3 factorial design with verbal modality (on-screen text procedure vs. auditory procedure) and the format of visual representation (static visual representation vs. static visual representation with motion cues vs. animated visual representation). After they completed their learning session, the ability to perform the procedural task was directly measured in a realistic setting. The results revealed that: (1) in the condition of static visual representation, the high spatial ability group outperformed the low spatial ability group, (2) for the low spatial ability participants, the animated visual representation group outperformed the static visual representation group, however, the static visual representation with motion cues group did not outperform the static visual representation group, (3) the use of animated visual representation helped participants with low spatial ability more than those with high spatial ability, and (4) a modality effect was found for the measure of satisfaction when viewing the animated visual representation. Since the participants with low spatial ability benefited from the use of animation, the results might support an idea that people are better able to retrieve the procedural information by viewing animated representation. The findings also might reflect a preference for the auditory mode of presentation with greater familiarity with the type of visual representation.     

3D visual comfort assessment by measuring the vertical disparity tolerance

Misalignment in stereo images leads to 3D discomfort, but the visual tolerance for disparities varies with viewing environment and stimulus. The aim of the study was twofold: first, to assess if vertical disparity tolerance (VDT) could be a reliable indicator of 3D visual comfort under certain restrained condition when vertical disparity is induced; second, to be able to predict how viewing conditions can affect visual comfort using an analytical model. Two viewing condition parameters were considered: luminance and stimulus angular size. The study was carried out in two experiments involving 17 subjects. In Experiment 1, visual comfort and vertical disparity tolerance were measured by a series of psychophysical tests for different stimulus angular sizes and luminance. Based on a regression analysis of this data, a model was proposed to estimate VDT as a function of luminance and stimulus angular size. In Experiment 2, a validation test was carried out to assess the quality of the model. Results confirm that for given viewing conditions (luminance, angular size, induced vertical disparity), the visual comfort measured is in agreement with the one predicted (ρ = 1.0008, p = 0.0026). VDT is a recognized reliable indicator of visual comfort due to vertical disparity and the model can be used to predict visual comfort for given viewing conditions.     

Display Movement Velocity and Dynamic Visual Search Performance

In practice, many visual search tasks are performed under dynamic conditions. An experiment was conducted here to test visual search strategy adopted by a person in a dynamic visual search and to investigate the effects of display movement velocity on search time and detection accuracy in it. Thirty‐five participants were randomly tested with all 10 angular velocities of 0, 2, 4, 6, 8, 10, 12, 14, 16, and 32 deg/s. The data obtained fitted the random search model well. The results revealed that observers utilized a random search strategy during the dynamic visual search process and that display movement velocity influenced search performance. In comparison with static visual search, an angular velocity faster than 4 deg/s resulted in a significant decrement in search performance. The variations of duration of individual fixations, the probability of target detection in a single fixation and visual lobe area were discussed. The obtained relationships between display movement velocity, search time and detection accuracy can serve as a useful guide for designing a dynamic search task, thus helping to maximize the cost‐effectiveness of dynamic search tasks while minimizing errors and misses during the search process.     

Relationships between maximum holding time and ratings of pain and exertion differ for static and dynamic tasks

Ratings of perceived discomfort (0 to 10 scale) have been used to estimate relative maximum holding times (%MHT), particularly for static tasks. A linear 1:10% ratio has been described, where a rating of 5 corresponds to 50%MHT. It is unknown whether this linear ratio is valid for dynamic tasks. Additionally, whether pain or exertion are the primary predictors of discomfort is not clear. Thus, the goal of this study was to investigate both pain and exertion ratings during static (50% maximum; N = 42) and dynamic (75% maximum; N = 34) elbow flexion tasks until failure. Gender, self-reported physical activity, and peak torque were also assessed. Pain and exertion ratings reasonably matched the 1:10% ratio during the static task but not during the dynamic task. Exertion related more strongly to MHT than pain in both tasks. Neither gender nor activity level appeared to influence perceptual ratings, but peak torque explained approximately 20% of the variance in MHT.     

A Computational Model of “Active Vision” for Visual Search in Human–Computer Interaction

Human visual search plays an important role in many human–computer interaction (HCI) tasks. Better models of visual search are needed not just to predict overall performance outcomes, such as whether people will be able to find the information needed to complete an HCI task, but to understand the many human processes that interact in visual search, which will in turn inform the detailed design of better user interfaces. This article describes a detailed instantiation, in the form of a computational cognitive model, of a comprehensive theory of human visual processing known as “active vision” (Findlay & Gilchrist, 2003). The computational model is built using the Executive Process-Interactive Control cognitive architecture. Eye-tracking data from three experiments inform the development and validation of the model. The modeling asks—and at least partially answers—the four questions of active vision: (a) What can be perceived in a fixation? (b) When do the eyes move? (c) Where do the eyes move? (d) What information is integrated between eye movements? Answers include: (a) Items nearer the point of gaze are more likely to be perceived, and the visual features of objects are sometimes misidentified. (b) The eyes move after the fixated visual stimulus has been processed (i.e., has entered working memory). (c) The eyes tend to go to nearby objects. (d) Only the coarse spatial information of what has been fixated is likely maintained between fixations. The model developed to answer these questions has both scientific and practical value in that the model gives HCI researchers and practitioners a better understanding of how people visually interact with computers, and provides a theoretical foundation for predictive analysis tools that can predict aspects of that interaction.     

GPU-based parallel vertex substitution algorithm for the p-median problem

We introduce a GPU-based parallel vertex substitution (pVS) algorithm for the p-median problem using the CUDA architecture by NVIDIA. pVS is developed based on the best profit search algorithm, an implementation of vertex substitution (VS), that is shown to produce reliable solutions for p-median problems. In our approach, each candidate solution in the entire search space is allocated to a separate thread, rather than dividing the search space into parallel subsets. This strategy maximizes the usage of GPU parallel architecture and results in a significant speedup and robust solution quality. Computationally, pVS reduces the worst case complexity from sequential VS’s O(p · n²) to O(p · (n ? p)) on each thread by parallelizing computational tasks on GPU implementation. We tested the performance of pVS on two sets of numerous test cases (including 40 network instances from OR-lib) and compared the results against a CPU-based sequential VS implementation. Our results show that pVS achieved a speed gain ranging from 10 to 57 times over the traditional VS in all test network instances.     

Effects of curved computer displays on visual performance,visual fatigue,and emotional image quality

This study investigated the effects of the curvature of curved computer displays on the visual performance, fatigue, and emotional image quality experienced by users during the performance of visual tasks. The characteristics of curved displays were compared and analyzed for different curvatures to investigate whether the curved displays showed improvements in terms of convenience of use when compared with flat displays. The visual performance results for the evaluated displays can be classified into three groups according to their response times, as (2000R = 2500R) > (3000R) > (3800R = 4500R = Flat). The visual fatigue results for average pupil size during a search task was 3.468 mm for flat and 3.355 mm for 2000R. This means that a 2000R curved display was found to be easier to use and thus generated less visual fatigue than a flat display when performing the same visual search task. Further, the results indicated that visual performance improved and visual fatigue decreased significantly as curvature increased. In this study, a curvature limit of 1700R was derived, when considering the image distortion of a 34‐in 21:9 curved display, and there was found to be no difference in the emotional image quality at curvatures greater than 2000R.     

On the correlation between children's performances on electronic board tasks and nonverbal intelligence test measures

In this study it was investigated whether a tangible electronic console (TagTiles) can be used in principle to address a range of cognitive skills by examining the underlying basic psychometric properties of TagTiles tasks. This is a precursor to an intervention study on the impact of TagTiles on cognitive development or an instrument development study. The tasks implemented on the console consisted of abstract visual patterns, which were intended to target perception, spatial knowledge representation, eye-hand coordination, reasoning and problem solving. The results of a pilot study (N = 10, children aged 8–10) and an experiment (N = 32, children aged 8–10) are presented. Correlations between scores on TagTiles tasks on the one hand and a selection of WISC-III^NL performance subtests, Raven's progressive matrices and RAKIT's Memory Span on the other hand, were calculated. The results indicate that the TagTiles tasks cover similar skills as the applied WISC-III^NL subtests, demonstrated by the moderate to large correlations between performance scores on sets of TagTiles tasks and sets of WISC-III^NL tasks. The combined TagTiles task scores were also significantly correlated with the aggregated WISC-III^NL subtest scores. Significant correlations were found between the TagTiles tasks and the Raven test scores, though for the RAKIT Memory Span no significant correlation with TagTiles tasks was found. After further refinement and validation, in particular with a larger sample size, the tasks can be applied to provide an indication of children's skill levels, offering the benefits of a self motivating testing method to children, and avoiding inconsistencies in administration. As such, the tasks may become an effective tool for the training and assessment of nonverbal skills for children.     

A 10-year assessment of information and communication technology tasks required in undergraduate agriculture courses

This study sought to assess required information and communication technology (ICT) tasks in selected undergraduate agriculture courses in a land-grant university during a 10-year period. Selected agriculture faculty members in the fall 1999 (n = 63), 2004 (n = 55), and 2009 (n = 64) semesters were surveyed to determine the ICT tasks they required of students. There were significant (p < .05) increases in the number of required Internet and electronic mail tasks between 1999 and 2009; but no significant changes in the number of word processing, computer graphics, spreadsheet, database, or miscellaneous ICT tasks required over the period. In 1999, three specific tasks (receive electronic mail, search the Internet, and type a lab or project report) were required in more than 50% of courses; in 2009, these three tasks plus three additional tasks (send electronic mail, submit assignments as attached electronic mail files, and use Blackboard^© to acquire course information) were required in a majority of courses. Faculty with higher levels of self-perceived ICT skills and those teaching higher-level courses tended to require larger and more diverse sets of ICT tasks than other faculty. Course level explained the largest proportion of unique variance in the number of required spreadsheet, word processing, computer graphics, and miscellaneous ICT tasks. Self-perceived ICT skills and course level explained approximately equal amounts of the unique variance in total ICT tasks required. Both the quantity and complexity of ICT in undergraduate agriculture courses should be increased.     

Biomechanical analysis of upper trapezius,erector spinae and brachioradialis fatigue in repetitive manual packaging tasks: Evidence from Chinese express industry workers

This study aims to assess the effects of repetitive motion-induced fatigue during manual packaging on kinematics and muscle activity of the arm, back and shoulder. Eighteen participants performed a 60-min manual packaging task. Electromyography median frequency of RUT, RES, LES and RB decreased by 13.2% (p < 0.05), 12.8% (p < 0.05), 11.3% (p < 0.05) and 21% (p < 0.001), respectively over time. The head flexion and the right upper arm flexion angles significantly (p < 0.001) differed among different packaging sizes, and similar results were observed for left upper arm flexion and rotation. The trunk and pelvis angles significantly (p < 0.05) differed over time under three kinds of packaging. The results showed there was an increase in the rating of perceived exertion from 8.56 to 16.94 (p<0.01) during the task. The outcomes of this study indicate repetitive movements in the manual packaging task resulted in elevated prevalence of muscle discomfort in packaging workers, especially the right brachioradialis. Interventions such as specific work: rest ratios, workplace redesign should be explored to relieve muscle fatigue and discomfort.Relevance to industryFor workers performing repetitive manual packaging tasks, biomechanical analysis of different muscles groups can help in developing appropriate ergonomic interventions.     

Development of a tablet test for the precision assembly efficiency assessment

This study explored if an individual's aiming ability can be used to predict his or her overall performance in a precision assembly task. A tablet aiming test was developed. Ten participants in the Pilot group was asked to do both the tablet aiming test and the simulated assembly task to determine the number of trials that were required for participants to get familiar with each operation. Thirty participants in the Test group performed the both tasks at certain times based on the number of trials determined in the pilot test. Pearson correlation analysis shows that, among the seven performance measures extracted from the tablet aiming test, the Number of Miss (r = 0.39, p = 0.03), the Hit Rate (r = −0.38, p = 0.04), and the Miss Rate (r = 0.39, p = 0.03) each had a significant correlation with the time required to complete the simulated assembly task (p < 0.05). The findings provide insights into the potential development for predicting the efficiency of a precision assembly task.     

Effects of alcohol and caffeine on maritime navigational skills

Twelve experienced navigators participated in an experiment to determine the effects of alcohol, caffeine, and an alcohol + caffeine mixture on performance during the following tasks: visual search, the search and location of items on a navigational chart (chartsearch) and the solving of maritime navigational problems. Alcohol (75 ml) produced impairment in performance on visual search (p&lt; 0.05) and navigational problem-solving (p< 0.01). Caffeine was found to enhance performance on visual search (p< 0.05) but not on the chartsearch, although a significant correlation was found between performance on the two tests (p< 0.05). Caffeine was not found to improve the accuracy of navigational problem-solving (p> 0.05). Neither alcohol nor caffeine had any significant effect on the speed of problem-solving (p> 0.05).     

Manual card sorting compared to automatic card presentation for assessing visual lobe size

Abstract

Using a sample of 54 Hong Kong Chinese subjects a highly significant correlation was found between lobe area and search performance on a task where the stimulus presentation was controlled with a semi-automatic electro-mechanical ‘card changer’. By using the same stimulus material for determination of lobe size and search performance and by reducing the possibility of subjects using extreme search strategies, a 90s manual card sorting test was found to correlate significantly with the ‘card changer’ results and with lobe area. The good correlation with lobe area was obtained for a homogeneous group of subjects with respect to age and near acuity using a rapid and simple method of lobe area measurement. The visual lobe is a function of considerable importance for visual search and has been shown to be related to search performance in a variety of practical situations. It is suggested here that a card sorting task may be used to assess the relative extent of a person's visual lobe size for screening individuals involved in search tasks, or to assess the effects of training.     

The influence of the availability of visual cues on the accurate perception of spatial dimensions in architectural virtual environments

Several authors have observed that spatial dimensions tend to be underestimated in virtual environments. In this study, we hypothesize that the availability of visual cues in virtual environments has an influence on the accuracy of perception. An experiment was conducted to compare spatial perception in real and virtual environments that were modeled differently and visualized using a head-mounted display. Results suggest that the greater the availability of visual cues, the greater the level of accuracy in the estimates, especially for egocentric dimensions (p < 0.001). In the end, this study contributes to a better understanding of how architectural virtual environments should be modeled for use in professional or commercial applications where accurate and reliable simulations are required.     

Neck and shoulder muscle activity during standardized work-related postural tasks

The aim of the present study was to assess the activity levels of the sternocleidomastoid muscle and upper trapezius muscle during static postures under controlled and standardized conditions, and to determine whether the muscle activity differed between sexes. Electromyographic (EMG) activity was recorded unilaterally from the sternocleidomastoid and upper trapezius muscle in 17 participants whilst they were performing various postural tasks. EMG amplitude was measured by the root mean square values of the raw signals and normalized to peak maximum contractile values for each muscle (%MVC). The intensity of muscle activity was ranked as light (<3%MVC), moderate (3%MVC ≤ EMG ≤ 8%MVC), and substantial (>8%MVC). During most tasks the two muscles contracted light to moderately. Head leaning and shoulder shrugging postures yielded substantial muscle activity in both muscles. Muscle activity did not differ significantly between male and female participants (F = 3.1; p = 0.078). Our findings provided normative values, which will enhance future studies of muscle activity during work in a natural, unrestrained environment.     

Differences in computer exposure between university administrators and CAD draftsmen

This study utilized an external logger system for onsite measurements of computer activities of two professional groups—twelve university administrators and twelve computer-aided design (CAD) draftsmen. Computer use of each participant was recorded for 10 consecutive days—an average of 7.9 ± 1.8 workdays and 7.8 ± 1.5 workdays for administrators and draftsmen, respectively. Quantitative parameters computed using recorded data were daily dynamic duration (DD) and static duration, daily keystrokes, mouse clicks, wheel scrolling counts, mouse movement and dragged distance, average typing and clicking rates, and average time holding down keys and mouse buttons. Significant group differences existed in the number of daily keystrokes (p < 0.0005) and mouse clicks (p < 0.0005), mouse distance moved (p < 0.0005), typing rate (p < 0.0001), daily mouse DD (p < 0.0001), and keyboard DD (p < 0.005). Both groups had significantly longer mouse DD than keyboard DD (p < 0.0001). Statistical analysis indicates that the duration of computer use for different computer tasks cannot be represented by a single formula with same set of quantitative parameters as those associated with mouse and keyboard activities. Results of this study demonstrate that computer exposure during different tasks cannot be estimated solely by computer use duration. Quantification of onsite computer activities is necessary when determining computer-associated risk of musculoskeletal disorders. Other significant findings are discussed.     

Visually deficient working conditions and reduced work performance in office workers: Is it mediated by visual discomfort?

IntroductionThe main purpose of this cross-sectional study was to investigate whether visual discomfort acts as a mediating factor between perceived visual ergonomic working conditions and self-rated visual performance among office workers who carry out administrative tasks and computer-based work at the Swedish Tax Agency.MethodsA questionnaire was sent to 94 office workers addressing: 1) perceived visual quality of the visual display units; 2) prevalence of eye symptoms; and 3) self-rated visual performance. Eighty-six persons (54 women (63%), 31 men (36%), and 1 of unspecified sex) answered the questionnaire. Multiple regression analysis investigated the association between visual ergonomic working conditions and visual performance, both with and without visual discomfort as a mediator.ResultsThe group mean of the Indexed survey questions indicated a reasonably good quality of visual ergonomic working conditions, a relative absence of eye symptoms, and acceptable self-rated visual performance. Results from multiple regression analysis showed a significant association between perceived visual ergonomic working conditions and self-rated visual performance (r² = 0.30, β = 0.327, p < 0.01). When visual discomfort was used as a mediator, the association between perceived visual ergonomic working conditions and self-rated visual performance remained the same (r² = 0.32, β = 0.315, p < 0.01).DiscussionIt was remarkable to discover that self-rated visual performance was independent of visual discomfort. Possible explanations include exposure factors not included in the current study, such as dry air and sensory irritation in the eyes, psychosocial stress, time spent performing near work activities, or time exposed to visually deficient working conditions.Relevance to industryThe strong connection between satisfaction with visual ergonomic working conditions and productivity in this study has implications for workplace profitability and staff satisfaction. If productivity is enhanced by better visual ergonomic working conditions, then managers of workplaces may be able to improve work outcomes by optimizing the physical work environment.     

Visual performance on synchronous and asynchronous peripheral target detection tasks

Horizontal visual lobe boundaries were measured for a peripheral target detection task using synchronous and asynchronous target presentation. The peripheral target was presented either at the beginning or end of stimulus presentation at one of three different target exposure durations for asynchronous presentation. Correct responses for the synchronous presentation were found to be much lower than that for the asynchronous one. With asynchronous presentation, exposure duration was important but not directly related to detection performance. Instead, timing of onset or offset of the target during presentation was found to affect detection performance. The results show that it is not appropriate to generalize the results of visual lobe tests obtained at static condition for visual search tasks containing dynamic content. © 1997 John Wiley & Sons, Inc.     

The effects of presentation method and information density on visual search ability and working memory load

This study investigates the effects of successive and simultaneous information presentation methods on learner’s visual search ability and working memory load for different information densities. Since the processing of information in the brain depends on the capacity of visual short-term memory (VSTM), the limited information processing capacity of learners may affect the visual search ability and working memory load differently for successive and simultaneous presentations. A change-detection experiment was conducted in this research to analyze visual search ability and working memory load. Two 4 × 4 dot arrays with three information densities were designed for the two presentation methods to test twenty-two participants. The results of the study indicated significant differences between the visual search abilities and the working memory loads for the two types of presentations at higher levels of information densities. Furthermore, significant differences were identified between visual search abilities for different information densities, due to the limited capacity of VSTM. The correlations of visual search ability and working memory load showed that the attention of the learners with higher visual search ability and lower working memory loads would perform better than the learners with lower visual search ability and higher working memory load.