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This session looks to serve the purpose of recalling and recounting the life and contributions of Professor John Senders. The contributors to this session include his direct colleagues, his students, his co-authors, those whom he inspired, and even members of his family. These designations are not exclusive! Senders made so many contributions across virtually a century of his lifetime that we are constrained to provide only selective highlights in this memorial session, such as John being named the winner of an “Ig-Nobel” Award. We shall each survey particular works which influenced us, but interweave those observations with personal experiences that can serve to reveal John the character, who was so much more than the simple written record that he has left behind.

Objective The present study tests the hypothesis that humans are capable of predicting the state of a system during visual occlusion, an assumption often made in models of sampling behaviour, but seldom tested. Background In 1967, John Senders introduced the visual occlusion paradigm to evaluate attentional demand of tasks such as automobile driving. Despite multiple studies employing this paradigm, the concept of operators actually being able to resolve uncertainty during occlusion by predicting system output has remained unvalidated. Method A self-paced visual occlusion monitoring task was contrived, involving a randomly rotating basin with a ball at the bottom. Participants were required to detect critical events (ball falling off the edge) while looking only as often as subjectively deemed necessary. Assuming the need to resolve uncertainty imposed by the random rotations, we examined relations between occlusion durations and system states preceding occlusion, for different glance durations, to infer whether predicting may have taken place. Results Results suggested that glance requests were consistent with the use of simple first order predictions. This pertained not only for longer (300 and 500 ms) glances, but even for 100 ms glances whenever critical events were imminent. Conclusion The presumption that human operators are capable, under certain circumstances, of predicting system state in the absence of visual information appears feasible; however, glance duration plays an important role. Applications By providing support for some of its basic premises, the use of Senders’ visual occlusion paradigm as a potential tool for evaluating human monitoring performance has been strengthened.

This article addresses some of the challenges involved with creating a stereoscopic video augmented reality “X-ray vision” display for near-field applications, which enables presentation of computer-generated objects as if they lie behind a real object surface, while maintaining the ability to effectively perceive information that might be present on that surface. To achieve this, we propose a method in which patterns consisting of randomly distributed dots are overlaid onto the real surface prior to the rendering of a virtual object behind the real surface using stereoscopic disparity. It was hypothesized that, even though the virtual object is occluding the real object’s surface, the addition of the random dot patterns should increase the strength of the binocular disparity cue, resulting in improved performance in localizing the virtual object behind the surface. In Phase I of the experiment reported here, the feasibility of the display principle was confirmed, and concurrently the effects of relative dot size and dot density on the presence and sensitivity of any perceptual bias in localizing the virtual object within the vicinity of a flat, real surface with a periodic texture were assessed. In Phase II, the effect of relative dot size and dot density on perceiving the impression of transparency of the same real surface while preserving detection of surface information was investigated. Results revealed an advantage of the proposed method in comparison with the “No Pattern” condition for the transparency ratings. Surface information preservation was also shown to decrease with increasing dot density and relative dot size.

BackgroundMany interventions have been implemented to improve hand hygiene compliance, each with varying effects and monetary costs. Although some previous studies have addressed the issue of conspicuousness, we found only 1 study that considered improving hand hygiene by using flashing lights.MethodOur attention theory–based hypothesis tested whether a simple red light flashing at 2-3 Hz affixed to the alcohol gel dispensers, within the main hospital entrance, would increase hand hygiene compliance over the baseline rate. Baseline and intervention observations were completed over five 60-minute periods (Monday-Friday) from 7:30 to 8:30 AM using a covert observation method.ResultsBaseline hand hygiene compliance was 12.4%. Our intervention increased compliance to 23.5% during cold weather and 27.1% during warm weather. Overall, our pooled compliance rate increased to 25.3% (P < .0001).ConclusionsA simple, inexpensive flashing red light affixed to alcohol gel dispensers was sufficiently salient to approximately double overall hand hygiene compliance within the main hospital entrance. We hypothesize that our intervention drew attention to the dispensers, which then reminded employees and visitors alike to wash their hands. Compliance was worse during cold days, presumably related to more individuals wearing gloves.

A two phase project is described for redesigning and evaluating paramedic response bags, one of the key pieces of equipment used by emergency medical services. Adopting a user-centred approach, Phase I involved first educating active service paramedics about ergonomic principles, and then collaborating with them to conceptualise a new type of response bag, based on separate colour coded kits, each containing related equipment items. Phase II describes a formal evaluation study, involving simulated procedures with a patient mannequin and active service paramedics in a real ambulance. Results indicated subjective preferences for the new bags, where 62% of the paramedics believed it was easier to find equipment in the new bag and 65% preferred the new bags overall. No detrimental effects were attributed to the transition to the new bag. Also discussed are the advantages of the participatory design approach, as well as design guidelines and implications for paramedic operations.

Objective: This study examined the concept of dynamic viewpoint tethering for enhancing performance in 3-D avatar control tasks. Background: Dynamic viewpoint tethering refers to a viewpoint animation technique that couples a display viewpoint to a controlled avatar through a virtual tether. A dynamic tether, modeled as a mass spring damper system, can potentially generate desirable viewpoint behavior because of its ability to produce frequency-separated viewpoint responses. This study investigated the impact of a tether’s rigidity and damping properties on users’ navigational performance. Methods: Twelve participants took part in a simulated 3-D aerial navigational task. Performance was evaluated with respect to local guidance and global awareness. Results: Root mean square error scores revealed a decrease in local guidance performance when (a) the tether was either severely underdamped or overdamped and (b) the tether’s rigidity approached either zero or infinity. In addition, (c) global performance was better for higher-frequency forcing functions. Conclusion: Critical damping and medium rigidity can be optimized during design for enhancing users’ navigational efficiency. Application: Guidelines generated from this study support future viewpoint design in interactive virtual reality applications.

The concept of dynamically manipulating the optical looming cues of a lead vehicle's brake lights is investigated as a means of potentially reducing the frequency of rear-end collisions in automobile driving. In a low-fidelity driving simulator, 40 participants were instructed to follow a leading vehicle (LV) and appropriately respond to braking of the LV, under three visibility conditions: day, night-time with following vehicle (FV) headlights, and night-time without FV headlights. During some LV braking events, separation and size of the brake lights of the LV were expanded or contracted, by a nominally imperceptible amount, to simulate an effective virtual time shift in the headway of the LV. Results show that this manipulation was most effective for very poor visibility conditions: at night with no headlights, for which LV brake lights were most salient. When confronting a LV with expanding or contracting brake lights, subjects generally braked sooner or later respectively, in comparison with the no manipulation case. The concept shows some promise for causing drivers to brake sooner in emergencies.

Accurate measurement of growth in infants and children is important, as it reflects a child's nutritional status and overall health. Conventional methods of measuring length and height are challeng...

Field studies have frequently been advocated as a means for understanding cognitive activities in naturalistic settings. However, there are several fundamental obstacles that one has to overcome to conduct a field study. This paper discusses two of these obstacles in the context of studying problem solving in complex environments: defining goals of a field study and justifying methods used in data analysis. Based on our experience from a recently finished field study, we outline a framework for understanding the nature of field studies and suggest a specific approach to data analysis. We argue that the goal of field studies should not be limited to hypothesis testing, and that the process of data analysis in field studies can be viewed as an inductive abstraction process. Our field study is used to illustrate the abstraction approach to data analysis and how the obstacles in field studies were dealt with. Through these discussions, we encourage researchers to engage in more field studies.

Modern medical environments have seen an increase in technological complexity and pressures of handling more patients with fewer resources, resulting in higher demands on medical practitioners. Medical informatics designers will have to focus on the problem of organizing medical information more effectively to enable practitioners to cope with these challenges. This article addresses this research problem for the particular area of medical problem solving in patient care. First, we describe a traditional modeling approach for medical reasoning used as a basis for developing some decision support systems. We argue these models may be faithful to what is known about biomedical knowledge, but they have limitations for human problem solving, especially in unanticipated situations. Second, we present an ontological framework, known as the abstraction hierarchy (Rasmussen, IEEE Trans. Man. Cybernetics 15 (1985) 234-243), for integrating patient representations that are faithful to existing biomedical knowledge and that are consistent with what is known about human problem solving. Through an example of a critical event in the operating room, we reveal how this framework can support medical problem solving in unanticipated situations. Third, we show how to use these representations as a frame of reference for mapping medical roles, responsibilities, sensors, and controls in an operating room context. Finally, we provide some insight for medical informatics designers in using this framework to design novel training programs and human-computer displays.

Misalignments between display and control reference frames complicate execution of many remote control tasks by loading the operator's attentional resources with mental transformations. It is thus important to maintain alignment between an operator's controls and her view of the controlled object or task space. Maximising the operator's situational awareness within this task space by providing an optimal frame of reference also simplifies task execution. Traditional rigid tethering integrates desirable egocentric and exocentric aspects of a display by connecting an exocentric view of the task space to the system being controlled. This paper introduces the concept of dynamic tethering (a superset of rigid tethering) which also preserves the principle of the moving part while maintaining control-display motion compatibility. Two experiments are presented, which show that compliance with these principles decreases the frequency of control reversals, improves reaction times, and decreases the RMS error associated with tracking performance.

The primary objective of this simulator study was to examine how attentional demand during automobile driving changes as a function of vehicle speed, road curvature and lane width. Attentional demand was estimated quantitatively using self-paced visual occlusion during driving and was calculated as the percent of the time that the visual occlusion spectacles were open. The results revealed that, in accordance with earlier related studies in the literature, attentional demand increases as speed increases and as lane width decreases, and is also greater for curved as compared to straight road segments. Implications of the findings both for further research and practical road design are discussed.

Motivated by the need for human performance evaluations of advanced interface technologies, this paper presents an empirical evaluation of a 3D interface, from the point of view of both display and control, in a pursuit tracking experiment. The paper derives methods for decomposing tracking performance into six dimensions (three in translation and three in rotation). This dimensional decomposition approach has the advantage of revealing overall performance levels in the depth dimension relative to performance in the horizontal and vertical dimensions. With interposition, linear perspective, stereoscopic disparity and partial occlusion cues incorporated into a single 3D display system, subjects' tracking errors in the depth dimension were about 35% (with no practice) to 35% (with practice) larger than those in the horizontal and vertical dimensions. It was also found that subjects initially had larger tracking errors along the vertical axis than along the horizontal axis, likely due to their attention allocation strategy. Analysis of rotation errors generated a similar anisotropic pattern.

This paper reports on a field study of the behavior of anesthesiologists as expert practitioners in managing a class of complex systems: patients under general anesthesia and surgery. The anesthesiologists studied were found to make extensive use of preparatory strategies, which provided them with many types of resources, including potential problems to be dealt with, materials needed, contingency response plans, desired goals, and the errors that are likely to be committed, The process of preparing these resources usually started with the compilation and review of a set of points for consideration (PFCs). A conceptual model of human planning is proposed which challenges traditional views on problem solving and planning, The model accounts for not only the specific results obtained in this field study, but also for the functional role of planning behavior during interactions with dynamic and complex systems in general, an important aspect of problem solving which has direct implications for the design of human-machine interfaces and cognitive support systems.

A quantitative description of the human information processor is required for predicting operator workload and performance from the simulated task time line data generated by task network models and related methods. Although many models of workload exist, few appear to be well founded in theory or to provide a satisfactory basis for a quantitative representation of operator load. Adherents of both time-and intensity-based models of operator load individually claim success for their methods. which might suggest that both factors are operating in determining operator workload and performance. This paper describes a study that explicitly investigates the relationship between a time-based factor and an intensity-based factor (amount of information to be processed) within a simulated air traffic control environment. A model is developed that posits that the load on the human information-processing system results directly from the ratio of the time necessary to process the required information to the time allowable for making a decision. This ratio, which can be identified with time pressure, determines subjective estimates of workload as well as operator performance. The model is tested against the data from the air traffic control simulation.

A series of three experiments investigated the effectiveness of stereoscopic and rotational display techniques for the purpose of establishing human factors guidelines for the design of three-dimensional (3D) displays. In the described experiments, depth perception was evaluated by examining accuracy in a 3D path-tracing task, with stimulus displays resembling the structure of cerebral angiograms. The first experiment allowed subjects to control rotation in dynamic displays. The results indicated that performance improved using either technique relative to viewing two-dimensional (2D) displays. However, rotational displays were superior to stereoscopic displays, and performance was best when both techniques were combined. The second experiment compared subject-controlled rotation with observation of continuously rotating displays at different rates of rotation. Performance declined at faster rotation rates; however, there were no advantages of subject-controlled rotation. In the third experiment, performance in rotational displays was no better than that in stereoscopic displays enhanced with multiple static viewing angles. However, performance was always best when both 3D techniques were jointly implemented. The results are discussed in terms of the visual information available using either 3D display technique and are related to the weighted additive model of depth perception.

A mathematical multipath model of the flow of information within the afferent limb of the myotatic stretch reflex is reviewed and evaluated, with emphasis being placed on its multi-channel structure. The system is simulated, and the resultant output (alpha motoneuron transmembrane potential) is analyzed spectrally, with one single-tone input (muscle stretch) and a set of variations of different system parameters: (i) When all the channels are identical, the characteristics of the input signal are unrecognizable at the output, and can only be extracted by an ``unphysiological'' motoneuron. (ii) When the afferent conduction delays are distributed among the channels, the output is similarly distorted, and can only be improved by assuming an atypically long conduction path. (iii) When the muscle spindle firing thresholds are either varied among the channels or vary temporally within each channel, the distortion is dramatically reduced and the input signal is easily recoverable.

Field-sequential stereoscopy, an increasingly accepted means of displaying three-dimensional visual images, is reviewed. The conventional electrooptic shutter devices used for viewing such displays employ either twisted nematic liquid crystals or PLZT ceramics. Both of these methods suffer the drawback of severe reduction in the brightness of the display image being observed. To overcome this problem, a field-sequential stereoscopic viewing apparatus employing light-scattering cholesteric liquid crystals is proposed. Advantages of this device include minimal reduction in image brightness, full colour and reduced visual fatigue.

A spectacle-mounted shuttering device, the Portable Liquid-crystal Apparatus for Tachistoscopy via visual Occlusion, based on light-scattering cholesteric liquid crystals, is introduced. Operating characteristics of the device are discussed with respect to the design objectives of comfort, switching speed, light transmission, light extinction, safety, and reliability. A number of practical research, clinical, and industrial applications of the spectacles as tachistoscope, stroboscope, and stereoscopic viewing apparatus are summarized.

A preview prediction model is used to describe the potential role of a fixed control strategy in automobile driving. On the basis of this model the time-to-line-crossing (TLC) concept was developed, representing the time necessary for the vehicle to reach either edge of the driving lane. An experiment on straight road driving was conducted to analyze whether TLC would be helpful to understand a driver's strategy in an occlusion task. The results indicate a close correspondence between TLC and driver's self-chosen occlusion times. In addition to conventional measures such as lateral position data, TLC seems a valuable description of driving performance.

An algorithm is presented for estimating the time course of intracellular generator potentials on the basis of the times of occurrence of evoked neural impulses, under conditions of external sinusoidal stimulation, and assuming SS-IPFM encoding. Recorded neural pulses are applied to the output of a theoretical SS-IPFM encoder (``in reverse'') and a least-squares criterion is adopted for estimating the input sinusoid and its harmonics which would have given rise to the same train of pulses. Illustrative simulation examples of the algorithm are given, and its practical applications are discussed.