The effects of target location and target distinction on visual search in a depth display

Research of human-centered computing systems in industry should not avoid advances in visual display technology for safety, warning, and interaction. Novel 3D displays that present information in real depth offer potential benefits. Previous research has studied depth in visual search but depth was mostly not realized by real physical separation. Many areas of Human Factors could be augmented with the study and evaluation for operation of novel 3D displays. Such a study was presented to better understand the effects of real physical depth in association with depth redundantly coded with another feature (an additional mark on a target) distinguishing it from distracters and target location on visual search in a depth display. Target location was studied as the row or column in the visual field of view the target was positioned and also in terms of eccentricity outwardly from the center of the display. In general, depth was found to be of benefit when redundantly coded with another attribute for guiding attention. Targets were not found as fast when the target’s location was further from the center fixation point, and interactions between target distinction (depth, mark, or depth+mark) and target location provide implications for designers.     

The degree of human visual attention in the visual search

Human beings can obtain visual information in parallel through the retina, but they cannot pay attention to all the information at the same time. In psychological studies, the human characteristics of visual attention have often been investigated by analyzing the characteristics of the visual search task. Previous studies suggested that the information features of the visual search task are processed in parallel at early stages of processing. However, the authors consider that these features are not processed completely in parallel, and have a reciprocal action to each other. In order to clarify the reciprocal action of the features in a visual search and the continuity of visual attention, the characteristics of reaction times were measured with changing forms of visual stimuli. The experimental results suggested that the reaction time changed when the features of the visual stimuli in the visual search task changed. This means that the features are affected by each other. Furthermore, continuity of reciprocal action is also suggested, and the degree of visual attention is decided by this continuity. The results provided significant basic data to support our proposed mathematical model of visual attention. This work was presented, in part, at the Fourth International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–22, 1999     

The effects of link format and screen location on visual search of web pages

Navigation of web pages is of critical importance to the usability of web-based systems such as the World Wide Web and intranets. The primary means of navigation is through the use of hyperlinks. However, few studies have examined the impact of the presentation format of these links on visual search. The present study used a two-factor mixed measures design to investigate whether there was an effect of link format (plain text, underlined, bold, or bold and underlined) upon speed and accuracy of visual search and subjective measures in both the navigation and content areas of web pages. An effect of link format on speed of visual search for both hits and correct rejections was found. This effect was observed in the navigation and the content areas. Link format did not influence accuracy in either screen location. Participants showed highest preference for links that were in bold and underlined, regardless of screen area. These results are discussed in the context of visual search processes and design recommendations are given.     

基于增量记忆视觉注意模型的复杂目标识别研究

针对复杂背景下的目标识别问题,提出一种新的基于增量记忆的视觉注意模型。首先根据目标的颜色形状,以及自底向上的原始视觉特征颜色、强度、方向、对称性对目标进行粗定位。在此基础上,利用粗选目标的颜色、形状生成一组自顶向下的偏差信号,对初选目标进行及时指导修正。为了提高识别的准确率,算法设计了一种增量学习记忆的机制来指导偏差信号,所提出的增量注意机制不仅可以不断学习和记忆各类目标的颜色和形状特征,而且利用这种机制可生成一个自顶向下的偏差信号,对关注的候选区域的目标进行精确定位。此外,训练后的增量记忆的颜色、形状特征有助于推断新的未知目标。最后的仿真实验中,与五种典型算法对比,无论是主观还是客观实验,都获得了较优结果。因此,所提算法是一种高效的、切实可行的算法。     

Regional bit allocation with visual attention and distortion sensitivity

This paper proposes a regional rate allocation method for enhancing the perceived quality in image compression. Bit allocation to image regions should be performed by considering the viewer’s attention and distortion sensitivity maps in order to address subjective quality concerns. The paper first proposes an exponential model for the relation between the viewer’s fixation duration and perceived information. The human visual system is more sensitive to the distortion around edges than the distortion in complex textured regions. Therefore, a novel distortion sensitivity method is also proposed that distinguishes true edges from complex textures without using edge detectors or gradient magnitude thresholds. The estimates for the visual attention level and the distortion sensitivity level are jointly used to modify the distortion contribution of each codeblock for determining its quantization parameter. The experiments validate the improved perceptual quality of decoded images due to the integrated use of the visual distortion sensitivity and the visual attention level in bit allocation. Moreover, the proposed bit allocation method is experimentally shown to yield a substantially higher subjective evaluation score than the other well-known bit allocation methods based on post-compression rate-distortion optimization, saliency maps, foveation of fixations and foveated just-noticeable-difference maps.

     

Vigilance, visual search and attention in an agricultural task

In a fragile agricultural environment, such as Western Australia (WA), introduced exotic plant species present a serious environmental and economic threat. Skeleton weed, centaurea juncea, a Mediterranean daisy, was accidentally introduced into WA in 1963. It competes with cash crops such as wheat. When observed in the fields, farms are quarantined and mechanised teams search for the infestations in order to destroy them. Since the search process requires attention, visual search and vigilance, the present investigators conducted a number of controlled field trials to identify the importance of these factors in detection of the weed. The paper describes the basic hit rate, vigilance decrement, effect of search party size, effect of target size, and some data on the effect of solar illumination of the target. Several recommendations have been made and incorporated in the search programme and some laboratory studies undertaken to answer questions arising.     

Superimposition, symbology, visual attention, and the head-up display

In two experiments we examined a number of related factors postulated to influence head-up display (HUD) performance. We addressed the benefit of reduced scanning and the cost of increasing the number of elements in the visual field by comparing a superimposed HUD with an identical display in a head-down position in varying visibility conditions. We explored the extent to which the characteristics of HUD symbology support a division of attention by contrasting conformal symbology (which links elements of the display image to elements of the far domain) with traditional instrument landing system (ILS) symbology. Together the two experiments provide strong evidence that minimizing scanning between flight instruments and the far domain contributes substantially to the observed HUD performance advantage. Experiment 1 provides little evidence for a performance cost attributable to visual clutter. In Experiment 2 the pattern of differences in lateral tracking error between conformal and traditional ILS symbology supports the hypothesis that, to the extent that the symbology forms an object with the far domain, attention may be divided between the superimposed image and its counterpart in the far domain.     

Human performance in a multiple-task environment: Effects of automation reliability on visual attention allocation

Diagnostic automation has been posited to alleviate the high demands of multiple-task environments; however, mixed effects have been found pertaining to performance aid success. To better understand these effects, attention allocation must be studied directly. We developed a multiple-task environment to study the effects of automation on visual attention. Participants interacted with a system providing varying levels of automation and automation reliability and then were transferred to a system with no support. Attention allocation was measured by tracking the number of times each task was viewed. We found that participants receiving automation allocated their time according to the task frequency and that tasks that benefited most from automation were most harmed when it was removed. The results suggest that the degree to which automation affects multiple-task performance is dependent on the relative attributes of the tasks involved. Moreover, there is an inverse relationship between support and cost when automation fails.     

Adaptive particle allocation for multifocal visual attention based on particle filtering

When confronting floods of visual inputs, it is usually impossible for computers to examine all possible interpretations based on given visual data. Despite these computational difficulties, humans robustly perform accurate visual processing. One of the most important keys in human visual processing is attention control. In this article, we first suggest that the particle filter (PF) is a major candidate for a model of multifocal visual attention. PF is a method which approximates intractable integrations in incremental Bayesian computation by means of stochastic sampling. One of the major drawbacks of PFs is a trade-off between computational costs and tracking performance; a large number of particles are required for accurate and robust estimations of state variables, which is time-consuming. This study proposes a computational model for multifocal visual attention which deals with the cost-performance trade-off with a restricted computing resource (the number of particles). Simulation experiments of tracking two targets with only tens of particles demonstrate the feasibility of the model. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Visual attention in driving: the effects of cognitive load and visual disruption

OBJECTIVE: This study investigates the effect of cognitive load on guidance of visual attention. BACKGROUND: Previous studies have shown that cognitive load can undermine driving performance, particularly drivers' ability to detect safety-critical events. Cognitive load combined with the loss of exogenous cues, which can occur when the driver briefly glances away from the roadway, may be particularly detrimental. METHOD: In each of two experiments, twelve participants engaged in an auditory task while performing a change detection task. A change blindness paradigm was implemented to mask exogenous cues by periodically blanking the screen in a driving simulator while a change occurred. Performance measures included participants' sensitivity to vehicle changes and confidence in detecting them. RESULTS: Cognitive load uniformly diminished participants' sensitivity and confidence, independent of safety relevance or lack of exogenous cues. Periodic blanking, which simulated glances away from the road-way, undermined change detection to a greater degree than did cognitive load; however, drivers' confidence in their ability to detect changes was diminished more by cognitive load than by periodic blanking. CONCLUSION: Cognitive load and short glances away from the road are additive in their tendency to increase the likelihood of drivers missing safety-critical events. APPLICATION: This study demonstrates the need to consider the combined consequence of cognitive load and brief glances away from the road in the design of emerging in-vehicle devices and the need to provide drivers with better feedback regarding these consequences.     

Target acquisition with UAVs: vigilance displays and advanced cuing interfaces

Vigilance and threat detection are critical human factors considerations in the control of unmanned aerial vehicles (UAVs). Utilizing a vigilance task in which threat detections (critical signals) led observers to perform a subsequent manual target acquisition task, this study provides information that might have important implications for both of these considerations in the design of future UAV systems. A sensory display format resulted in more threat detections, fewer false alarms, and faster target acquisition times and imposed a lighter workload than did a cognitive display format. Additionally, advanced visual, spatial-audio, and haptic cuing interfaces enhanced acquisition performance over no cuing in the target acquisition phase of the task, and they did so to a similar degree. Thus, in terms of potential applications, this research suggests that a sensory format may be the best display format for threat detection by future UAV operators, that advanced cuing interfaces may prove useful in future UAV systems, and that these interfaces are functionally interchangeable.     

Visual search tasks: measurement of dynamic visual lobe and relationship with display movement velocity

Visual lobe is a useful tool for predicting visual search performance. Up till now, no study has focused on dynamic visual lobe. This study developed a dynamic visual lobe measurement system (DVLMS) that could effectively map dynamic visual lobe and calculate visual lobe shape indices. The effects of display movement velocity on lobe shape indices were examined under four velocity conditions: 0, 4, 8 and 16 deg/s. In general, with the increase of display movement velocity, visual lobe area and perimeter became smaller, whereas lobe shape roundness, boundary smoothness, symmetry and regularity deteriorated. The elongation index was not affected by velocity. Regression analyses indicated that display movement velocity was important in determining dynamic visual lobe shape indices. Dynamic visual lobe provides another option for better understanding dynamic vision, in addition to dynamic visual acuity. Findings of this study can provide guidelines for analysing and designing dynamic visual tasks.

Practitioner Summary: Dynamic visual lobe is important in reflecting the visual ability of searching for a moving target. We developed a dynamic visual lobe measurement system (DVLMS) and examined display movement velocity’s effects on lobe shape. Findings revealed that velocity was a key factor affecting dynamic visual lobe shape indices.     

An integrated measure of display clutter based on feature content,user knowledge and attention allocation factors

Existing measures of display clutter in the literature generally exhibit weak correlations with task performance, which limits their utility in safety-critical domains. A literature review led to formulation of an integrated display data- and user knowledge-driven measure of display clutter. A driving simulation experiment was conducted in which participants were asked to search ‘high’ and ‘low’ clutter displays for navigation information. Data-driven measures and subjective perceptions of clutter were collected along with patterns of visual attention allocation and driving performance responses during time periods in which participants searched the navigation display for information. The new integrated measure was more strongly correlated with driving performance than other, previously developed measures of clutter, particularly in the case of low-clutter displays. Integrating display data and user knowledge factors with patterns of visual attention allocation shows promise for measuring display clutter and correlation with task performance, particularly for low-clutter displays.

Practitioner Summary: A novel measure of display clutter was formulated, accounting for display data content, user knowledge states and patterns of visual attention allocation. The measure was evaluated in terms of correlations with driver performance in a safety-critical driving simulation study. The measure exhibited stronger correlations with task performance than previously defined measures.     

Peripheral visual feedback: a powerful means of supporting effective attention allocation in event-driven, data-rich environments

Breakdowns in human-automation coordination in data-rich, event-driven domains such as aviation can be explained in part by a mismatch between the high degree of autonomy yet low observability of modern technology. To some extent, the latter is the result of an increasing reliance in feedback design on foveal vision--an approach that fails to support pilots in tracking system-induced changes and events in parallel with performing concurrent flight-related tasks. One possible solution to the problem is the distribution of tasks and information across sensory modalities and processing channels. A simulator study is presented that compared the effectiveness of current foveal feedback and two implementations of peripheral visual feedback for keeping pilots informed about uncommanded changes in the status of an automated cockpit system. Both peripheral visual displays resulted in higher detection rates and faster response times, without interfering with the performance of concurrent visual tasks any more than does currently available automation feedback. Potential applications include improved display designs that support effective attention allocation in a variety of complex dynamic environments, such as aviation, process control, and medicine.     

Exploring the crossing behaviours and visual attention allocation of children in primary school in an outdoor road environment

Cognition, Technology & Work - Primary school children are likely to participate in traffic as pedestrian road users. Due to their immature levels of physical and cognitive development, it is...     

Relationships among display features, eye movement characteristics, and reaction time in visual search

The relative contribution of number of fixations and fixation duration to reaction time in visual search was investigated. Ten participants (age 20-24 years) took part in each of two experiments. In Experiment 1, the experimental factors were display type (icon and file name), organization (arrangements with and without grouping), and number of stimuli presented (4, 8, and 16). In Experiment 2, a search task for a target stimulus (three prespecified random letters) was conducted, and the experimental factor was the display's layout complexity. Multiple regression analysis was used to examine whether reaction time was explained by a mediational model in which reaction time is mediated by eye movements and display features are not directly related to reaction time. The mediational model was not supported, and the effects of display features on reaction time were not attributable solely to eye movements. The interaction between number of fixations and fixation duration was also explored as a function of display features. As the display feature changed and the task became more difficult, the contribution of the number of fixations to explain the variation in reaction time became dominant for both experiments. Potential applications include measurements of cognitive ability, eye muscle balance disorders, and binocular fusion ability.     

Display signaling in augmented reality: effects of cue reliability and image realism on attention allocation and trust calibration

This experiment seeks to examine the relationships among three advanced technology features (presentation of target cuing, reliability of target cuing, and level of image reality and the attention and trust given to that information). The participants were 16 military personnel who piloted an unmanned air vehicle and searched for targets camouflaged in terrain, which was presented at two levels of image realism. Cuing was available for some targets, and the reliability of this information was manipulated at two levels (100% and 75%). The results showed that the presence of cuing aided target detection for expected targets but drew attention away from the presence of unexpected targets. Cuing benefits and attentional tunneling were both reduced when cuing became less reliable. Increasing image realism was compelling but increased reliance on the cuing information when those data were reliable. Potential applications include a cost-benefit analysis of how trust modulates attention in the use of automated target recognition systems and the extent to which increased realism may influence this trust.     

Automation-induced monitoring inefficiency: role of display location

Operators can be poor monitors of automation if they are engaged concurrently in other tasks. However, in previous studies of this phenomenon the automated task was always presented in the periphery, away from the primary manual tasks that were centrally displayed. In this study we examined whether centrally locating an automated task would boost monitoring performance during a flight-simulation task consisting of system monitoring, tracking and fuel resource management sub-tasks. Twelve nonpilot subjects were required to perform the tracking and fuel management tasks manually while watching the automated system monitoring task for occasional failures. The automation reliability was constant at 87.5% for six subjects and variable (alternating between 87.5% and 56.25%) for the other six subjects. Each subject completed four 30 min sessions over a period of 2 days. In each automation reliability condition the automation routine was disabled for the last 20 min of the fourth session in order to simulate catastrophic automation failure (0 % reliability). Monitoring for automation failure was inefficient when automation reliability was constant but not when it varied over time, replicating previous results. Furthermore, there was no evidence of resource or speed accuracy trade-off between tasks. Thus, automation-induced failures of monitoring cannot be prevented by centrally locating the automated task.     

Limits of visual perception in the technology of visual display terminals

. The limits of visual perception in present VDT technology for man-machine communication are considered. Essentially, these limits concern the reading of the displayed information and follow from the prevailing display conditions as to (i) luminous contrast, (ii) character shape, (iii) text layout and (iv) text colour. The effect of these conditions on legibility is quantitatively described from research results, and practical suggestions are given for improving display legibility, through changes in contrast polarity, character shape, layout and the way colour is used. Finally, a plea is made for including experts in visual ergonomics in the teams developing new display devices in the future.     

Eyestrain and visual display units: a review

A review is presented of current knowledge about the nature, incidence and causes of eyestrain or visual fatigue among VDU operators. It is suggested that fatigue and discomfort may result from visual, postural, environmental, work design and personal factors. However, it is concluded that all these problems can be overcome by sufficient attention to ergonomics in the design, implementation and use of VDUs.