Showing papers in "Human Factors in 1995"

Toward a Theory of Situation Awareness in Dynamic Systems

Abstract: This paper presents a theoretical model of situation awareness based on its role in dynamic human decision making in a variety of domains. Situation awareness is presented as a predominant concern in system operation, based on a descriptive view of decision making. The relationship between situation awareness and numerous individual and environmental factors is explored. Among these factors, attention and working memory are presented as critical factors limiting operators from acquiring and interpreting information from the environment to form situation awareness, and mental models and goal-directed behavior are hypothesized as important mechanisms for overcoming these limits. The impact of design features, workload, stress, system complexity, and automation on operator situation awareness is addressed, and a taxonomy of errors in situation awareness is introduced, based on the model presented. The model is used to generate design implications for enhancing operator situation awareness and future directio...

Measurement of Situation Awareness in Dynamic Systems

Abstract: Methodologies for the empirical measurement of situation awareness are reviewed, including a discussion of the advantages and disadvantages of each method and the potential limitations of the measures from a theoretical and practical viewpoint. Two studies are presented that investigate questions of validity and intrusiveness regarding a query-based technique. This technique requires that a simulation of the operational tasks be momentarily interrupted in order to query operators on their situation awareness. The results of the two studies indicate that the query technique is not intrusive on normal subject behavior during the trial and does not suffer from limitations of human memory, which provides an indication of empirical validity. The results of other validity studies regarding the technique are discussed along with recommendations for its use in measuring situation awareness in varied settings.

The Out-of-the-Loop Performance Problem and Level of Control in Automation:

Abstract: The out-of-the-loop performance problem, a major potential consequence of automation, leaves operators of automated systems handicapped in their ability to take over manual operations in the event of automation failure. This is attributed to a possible loss of skills and of situation awareness (SA) arising from vigilance and complacency problems, a shift from active to passive information processing, and change in feedback provided to the operator. We studied the automation of a navigation task using an expert system and demonstrated that low SA corresponded with out-of-the-loop performance decrements in decision time following a failure of the expert system. Level of operator control in interacting with automation is a major factor in moderating this loss of SA. Results indicated that the shift from active to passive processing was most likely responsible for decreased SA under automated conditions.

How in the world did we ever get into that mode? Mode error and awareness in supervisory control

Abstract: New technology is flexible in the sense that it provides practitioners with a large number of functions and options for carrying out a given task under different circumstances. However, this flexib...

The Proximity Compatibility Principle: Its Psychological Foundation and Relevance to Display Design

Abstract: In this report we describe the concept of the proximity compatibility principle (PCP) and demonstrate its relevance to display design: Displays relevant to a common task or mental operation (close task or mental proximity) should be rendered close together in perceptual space (close display proximity). Different forms of task proximity are discussed, as are the different information-processing mechanisms that underlie the effects of the several different design manipulations of display proximity. Experimental data that support this process-based elaboration of PCP are then reviewed in design contexts relating to aviation, graphs, display layout, and decision aiding.

Situation Awareness in Team Performance: Implications for Measurement and Training:

Abstract: Situation awareness has long been recognized as an important variable in aviation performance. Research to date has focused on identifying characteristics of situation awareness for individuals, not on the behaviors and processes associated with team situation awareness. The purpose of this review is to delineate and identify characteristics of team situation awareness. In addition, implications are discussed and research questions are outlined that target the measurement and training of situation awareness in teams.

Situation Awareness Is Adaptive, Externally Directed Consciousness:

Abstract: Situation awareness (SA) is defined as adaptive, externally directed consciousness. This definition dispels the artificial and contentious division evident in the literature, according to which SA is either exclusively knowledge or exclusively process. This misdirected rivalry has more to do with general perspectives on the study of human behavior than with SA itself. Through defining SA as an aspect of consciousness, researchers clarify two key issues. First, the source of goals with respect to SA is a normative arbiter in the task environment; that is, the behavior that SA generates must be directed at an external goal. Second, SA is the invariant at the core of the agent's perception-action cycle that supports skilled performance; that is, relationships among factors or dimensions in the environment determine what the agent must know and do to achieve the goals specified by the external arbiter. Investigators introduce a construct called the risk space to represent the invariant relations in the environment that enable the agent to adapt to novel situations and to attain prespecified goals. Researchers articulate this concept of a risk space through use of a specific example in commercial aircraft operations. The risk space structures information about the physical airspace in a manner that captures the momentary knowledge that drives action and that satisfies the goals and performance criteria for safe and efficient flight. The authors note that the risk space may be generalized to many different means of navigation.

Situation Awareness and the Cognitive Management of Complex Systems

Abstract: The issue of how to support situation awareness among operators of complex systems or vehicles is a growing concern in a number of industries, especially when automation takes the operators partly ...

Situation Awareness in Anesthesiology

Abstract: Situation awareness has primarily been confined to the aviation field. We believe that situation awareness is an equally important characteristic in the complex, dynamic, and risky field of anesthesiology. We describe three aspects of situations of which the decision maker must remain aware: subtle cues, evolving situations, and special knowledge elements. We provide examples of real or simulated anesthesia situations in which situation awareness is clearly involved in the provision of optimal patient care, and we map the elements of situation awareness onto a cognitive process model of the anesthesiologist. Finally, we consider how situation awareness can be further investigated and taught in this medical domain using anesthesia simulators and analyses of real cases. The study of situation awareness in anesthesiology may provide a good example of the wider application of the concept of situation awareness to nonaerospace environments.

Situation awareness: proceed with caution

Abstract: Situation awareness (SA) is a relatively new concept that has captured the imagination of the human factors community. This new concept is considered in the light of Benton J. Underwood's discussio...

The measurement of team process.

Abstract: The construct validity of measures of team process was evaluated using predictive, known groups and multitrait-multimethod (MTMM) validation strategies. Military air crews (N = 51) flew two simulated missions. Independent judges provided evaluations of the same six team process variables in both scenarios. An MTMM analysis of judges' ratings treating judges as a method variable showed good convergent and discriminant validity. Judges' mean ratings of the six process variables were correlated with mission effectiveness. Some process measures discriminated between student and instructor teams, thus showing discrimination between known groups. Conversely, an MTMM analysis of ratings treating scenarios as a method showed poor convergent validity. We concluded that important team process behaviors have been identified and can be rated validly but that multiple observations are necessary to assess characteristics of individual teams with any accuracy. The discussion includes implications for practice and future research.

Social and Cognitive Processes in Interpersonal Communication: Implications for Advanced Telecommunications Technologies

Abstract: Interactive multimedia conferencing systems, in which two or more remotely located people can work on cooperative tasks through shared audio, video, and data, appear to be the wave of the future. However, because of great advances in the underlying technology of multimedia conferencing systems, many design decisions have been driven by what is technically feasible as opposed to what will best suit the needs of the users. In this paper we provide a framework for the design and evaluation of features in advanced telecommunications products and services which is derived from empirical research on interpersonal communication. We also discuss implications of this research for the development and use of advanced telecommunications technologies.

Measuring Knowledge Organization as a Method for Assessing Learning during Training

Abstract: This paper applies the conceptual work of K. Kraiger, J. K. Ford, and E. Salas (1993) to the evaluation of two training programs. A method known as structural assessment (SA) was described and adapted for use in the evaluation of a training program for computer programming and a PC-based simulation of a naval decision-making task. SA represents and evaluates pairwise judgments of relatedness of concepts drawn from the training content domain. In the first study, SA scores of students (determined by similarity to an expert solution) were significantly higher after training than before but did not predict performance on a take-home exam 12 weeks later. In the second study, we manipulated training content by providing half the students with the goals and objectives of the transfer task (an advance organizer) before training and providing the other half with the same information after training. As hypothesized, SA scores were higher for those receiving the organizers before training; SA scores were also more ...

Level of operator control and changes in heart rate variability during simulated flight maintenance

Abstract: The demands of dynamic monitoring and fault diagnosis for flight engineer trainees were examined in relation to changes in heart rate (HR) and two spectral analysis measures (midfrequency: 0.07-0.14 Hz; high frequency: 0.15-0.40 Hz) of heart rate variability (HRV). Eleven trainee flight engineers were studied, as part of their training and assessment, over three 3-h sessions in a cockpit simulator. During each session, faults and incidents programmed into the system had to be detected, diagnosed, and corrected. Electrocardiograms were taken, and each session was recorded on videotape. Work phases were classified from video analysis of flight maintenance activities, using Rasmussen's cognitive control taxonomy, into monitoring, routine (rule-based), and problem-solving (knowledge-based) phases. HR and HRV were found to be sensitive to different phases of the work environment. HRV was suppressed during the mentally demanding problem-solving mode of the level flight phase, but only for the midfrequency component. Elevated heart rate, in contrast, was associated with the more generally stressful takeoff and landing phases. The findings support both the use of HRV as a physiological index of mental effort and its value in operational contexts, and the value of ecologically derived methods of evaluating differences in work demands in complex systems.

Relative effects of age and compromised vision on driving performance

Abstract: The aim of this study was to determine the relative effects of age and compromised vision on driving-related skills and on-road accidents. A total of 107 subjects were tested. They represented four groups that varied in age and visual status, as follows: (1) a younger, normally sighted group; (2) an older, normally sighted group; (3) a younger, visually compromised group; and (4) an older, visually compromised group. Driving performance was assessed by self-reported and state-recorded accident frequency and by an evaluation of performance on an interactive driving simulator. The older groups had poorer driving-related skills, as measured with our interactive driving simulator, than had the younger groups, but they did not have significantly higher on-road accident rates than the younger groups. The older subjects and those with compromised vision had reduced risk-taking scores, as measured with a self-report questionnaire. In addition, all older drivers had increased eye movements and had slower simulator driving speeds, which suggests that behavioral compensation is made for visuocognitive/motor deficits. Regression analyses showed that compromised vision and visual field loss predicted real-world accidents in our study population.

Effects of instruction type and boredom proneness in vigilance: implications for boredom and workload.

Abstract: The present study examined the effects of instruction type and boredom proneness (BP) on vigilance performance, workload, and boredom. Subjects completed the Boredom Proneness Scale and were assign...

Telepresence in Videocommunications: A Study on Stereoscopy and Individual Eye Contact:

Abstract: We conducted two experiments to investigate how stereoscopy and technologies that allow individual eye contact affect the impression of telepresence in videoconferencing. Telepresence is defined as the degree to which participants of a telemeeting get the impression of sharing space with the remote site. Results revealed, among other things, that stereoscopy increases telepresence and makes videoconferencing more attractive. In addition, we found that reduced eye contact angles enhance the recognizability of individually addressed nonverbal signals. However, a setup that eliminates horizontal and vertical eye contact angles seems to be advantageous only in conferences with more than two persons per site.

Self-Selected Manual Lifting Technique - Functional Consequences of the Interjoint Coordination

Abstract: The pattern of movement self-selected by 39 subjects to lift light loads from 9 cm above the ground is described in kinematic and electromyographic terms. Hamstring length changes were estimated from hip and knee angular kinematics. Subjects adopted a posture at the start of the lift intermediate between stoop and full-squat postures. A consistent coordination between knee, hip, and lumbar vertebral joints during lifting was described through calculation of the relative phase between adjacent joints and found to be exaggerated with increases in load mass. During the early phase of lifting, knee extension leads hip extension, which in turn leads extension of the lumbar vertebral joints. Early in the lifting movement, when load acceleration is greatest, the erectores spinae are thus relatively long and shortening slowly. Both of these factors produce greater back extensor strength. Rapid hamstring shortening is also delayed, which enhances their strength, and coactivation of the monoarticular knee extensors and biarticular hamstrings observed early in the lifting movement suggested that the knee extensors contribute to hip extension through a tendinous action of the hamstrings.

Dual-task performance in space: results from a single-case study during a short-term space mission

Abstract: During spaceflights, astronauts are exposed to many stressors (e.g., microgravity, confinement) that may impair human information-processing capabilities. In order to analyze the possible effects of the space environment on human time-sharing efficiency, a single-case experiment was conducted in which the time course of dual-task performance (unstable tracking with concurrent memory search) of one space crew member was monitored repeatedly (13 times) throughout an 8-day space mission. Tasks were taken from the Advisory Group for Aerospace Research and Development battery of Standardized Tests for Research with Environmental Stressors. Comparisons of in-flight, preflight, and postflight performance revealed no decrements in single-task memory search performance but did reveal clear impairments in single-task tracking and dual-task performance. From these results we conclude that psychomotor processes and higher attentional functions are particularly prone to disturbance effects in space.

Symmetric and Asymmetric Two-Handed Pull-Push Strength of Young Adults

Abstract: Forty normal young adults volunteered for an experiment in which they were required to perform two-handed maximal pull-push in isometric and isokinetic modes (50 cm/s linear velocity of the handle) at 50-, 100-, and 150-cm heights of handle in sagittal, 30-deg lateral, and 60-deg lateral planes. Subjects were stabilized on a circular platform that rotated on its axis and allowed fixation in any position to achieve asymmetric settings. The pull-push strengths were applied to a 53-cm wide handle and were measured through the load cell assembly of the Static Dynamic Strength Tester. The peak and average strengths were compared statistically, and an ANOVA and multiple regression were performed. The main effects of gender, activity (pull or push), mode (isometric or isokinetic), plane (sagittal, 30 deg lateral, or 60 deg lateral), and height (low, medium, or high) of activity for both peak and average strengths were highly significant (p < 0.01). All subjects were strongest in pulling activity in the isometric mode in the sagittal plane at medium height. Males were significantly stronger than females for most activities. However, with increased postural asymmetry, the difference between genders declined.

Musical versus Visual Graphs: Cross-Modal Equivalence in Perception of Time Series Data

Abstract: By applying multidimensional scaling procedures and other quantitative analyses to perceptual dissimilarity judgments, we compared the perceptual structure of visual line graphs depicting simulated time series data with that of auditory displays (musical graphs) presenting the same data. Highly similar and meaningful perceptual structures were demonstrated for both auditory and visual modalities, showing that important data characteristics (function slope, shape, and level) were perceptually salient in either presentation mode. Auditory graphics may be a highly useful alternative to traditional visual graphics for a variety of data presentation applications.

Estimates of Driver Mental Workload: A Long-Term Field Trial of Two Subsidiary Tasks

Abstract: Two auditory subsidiary task measures of driver mental workload--delayed digit recall and random digit generation--were evaluated in a 4-year field trial. Van pool members performed the tasks for 2-minute periods while driving a mix of rural secondary roads, limited access expressways, high-density, limited-access urban drives, and downtown city streets on a daily commute from upstate New York to New York City. Data collected included the roadway being traveled, time of day, traffic conditions, vehicle density, speed, weather, brake applications, and driver's subjective difficulty rating. Subsidiary task degradation was a function of traffic density, average speed, and uncertainty. Weather conditions moderated these variables. Unpredictability of traffic appeared to be the major determinant of perceived difficulty. The digit recall task correlated with driver ratings of task difficulty and with a calculated driver workload index based on brake actuations per minute plus the log of vehicle speed. Although subjective difficulty ratings correlated with subsidiary task performance and with objective criteria of traffic density and speed, some dissociation was noted. Indications of workload homeostasis were evident, as drivers appeared to modify their performance to keep workload within a comfortable range.

Predictors of hearing protection use among workers: implications for training programs.

Abstract: In this study, we used the conceptual Health Promotion Model to identify predictors of hearing protection use among blue-collar workers (N = 504). The strongest predictors were self-efficacy, benefits, value, and barriers. Items in the barriers scale were most strongly correlated with use and had the greatest potential for change. Therefore, items from this scale are being used as the primary basis for development of a training intervention program.

Expert and Novice Recognition of Similar Situations

Abstract: Situation assessment is crucial for making schema-driven decisions in naturalistic settings. Recognizing that some situations are similar to a specific category of scenarios underscores the classification aspect. To test hypotheses regarding expert and novice differences in recognizing similar scenarios, 28 senior naval officers and 52 junior naval officers classified tactical situations, each of which appeared on a note card, labeled every created cluster to convey a category description, and signified their criteria for sorting scenarios. Principal-components and discriminant analyses, and associated statistics, established that when categorizing situations, experts and novices used surface features and deep structures as criteria for recognizing similarity; experts are significantly more context-dependent than are novices; experts and novices do not differ significantly in the number of schemata and scenarios per schema formed or in the access avenues ascribed for these schemata; experts do not process...

Special Issue Preface

Abstract: Although situation awareness (SA) has only recently become a subject of intense research, it was first recognized as early as World War I by Oswald Boelke (Press, 1986, as cited in Garland, Phillips, Tilden, and Wise, 1991).Boelke realized "the importance of gaining an awareness of the enemy before the enemy gained a similar awareness, and devised methods for accomplishing this" (Endsley, 1988, p. 97). Examples can be found in stories of the celebrated Red Baron, who reportedly could give accurate re-creations and critiques of his fellow pilots even though he was engaged in a dogfight hundreds of meters away. Today the conceptual basis of SA is cloudy. The increased research attention being paid to the construct has met with a fair amount of criticism. Much of the skepticism is founded in a number of epistemological and experimental arguments, which generally center on the assumption that it is too subjective a phenomenon to be measured objectively. Additionally, as pointed out in the antinomy contributed to this issue by John Flach, the causal inferences attributed to SA can be called into question on the grounds of circulari ty . However, as the following pages illustrate, others find SA a useful concept, something that has considerable significance for operational settings and thus constitutes a worthy research topic. Also, most agree that SA can be inferred from actions (e.g., those obtained in designed simulations) and that such inferences will eventually yield strong underpinnings for a theoretical account of the phenomenon. Aviation is a fitting context for the study of SA and constitutes a common theme throughout this special issue. Events happen fast in flight and require a rapid analysis of complex, dynamic scenarios; poor performance often extracts a high cost. The importance of understanding SA should become even greater as automation replaces manual control in more and more systems contexts. The sudden onset of alarms will demand that operators attain high levels of SA rapidly. The danger attendant upon an operator, acting as a supervisor, who loses awareness of a critical automated system model and fails to see why it has faltered is well recognized but still largely unresolved. SA was described in the U.S. Air Force's lntraflight Command. Control, and Communication Symposium Final Report (1986) as the single most important factor in improving mission effectiveness. To this end the U.S. Air Force has taken the lead in studying the measurement and trainability of SA (see Carretta, Perry, and Ree, 1994). In light of these considerations, the objective of this special issue is to examine the current status of SA both in theory and in application through a sampling of the many ongoing activities that have been prompted by the concept. The selected articles achieve this goal. In addition, they identify gaps in knowledge and needs for future work. SA clearly suffers from a lack of empirical data. I hope that these pages will stimulate more research aimed at clarifying the theoretical picture and that they will provide recommendations for transfer to current and future applications. The articles address domain exemplars, theory, measurement, individual training, team awareness, and challenges. The first two papers, by Nadine B. Sarter and David D. Woods and by David M. Gaba, Steven K. Howard, and Stephen D. Small, together serve to introduce the problems of and opportunities for SA and suggest its diverse applications with emerging systems. Domains as disparate as the flight deck and the operating room illustrate quite well that SA is not domain specific. The next three papers, two by Mica R. Endsley and the other by Marilyn Jager Adams, Yvette J. Tenney, and Richard W. Pew, give the current status of theory and measurement-key concerns for SA. Although Endsley proposes "stop

Judgments of Azimuth and Elevation as a Function of Monoscopic and Binocular Depth Cues Using a Perspective Display

Abstract: The purpose of this study was to investigate the use of three-dimensional display formats for judgments of spatial information using an exocentric frame of reference. Eight subjects judged the azimuth and elevation that separated two computer-generated objects using either a perspective or stereoscopic display. Errors, which consisted of the difference in absolute value between the estimated and actual azimuth or elevation, were analyzed as the response variable. The data indicated that the stereoscopic display resulted in more accurate estimates of elevation, especially for images aligned approximately orthogonally to the viewing vector. However, estimates of relative azimuth direction were not improved by use of the stereoscopic display. Furthermore, it was shown that the effect of compression resulting from a 45-deg computer graphics eye point elevation produced a response bias that was symmetrical around the horizontal plane of the reference cube, and that the depth cue of binocular disparity provided by the stereoscopic display reduced the magnitude of the compression errors. Implications of the results for the design of spatial displays are discussed.

Vigilance Latencies to Aircraft Detection among NORAD Surveillance Operators

Abstract: A function of North American Aerospace Defence (NORAD) in North Bay, Ontario, is to identify all aircraft entering Canadian airspace. The first step in performing this task is to detect visually the presence of aircraft from either radar or transponder information presented on display consoles. This challenging, real-world vigilance task was used to investigate factors affecting detection latencies. The experiment revealed that performance varied as a function of geographic area of coverage, the midnight shift was particularly sensitive to vigilance decrements, and a vigilance decrement effect can occur in a real-world task, but this effect is not as strong as those reported in laboratory studies.

Taxonomy of scheduling systems as a basis for the study of strategic behavior

Abstract: Strategic behavior is frequently characterized by the need to decide among several courses of action, each of which may lead to a desired goal, subject to time constraints. Often strategic behavior can be regarded as a series of answers to the question, "In what sequence should I perform the set of actions required, and when should I start and stop each of them?" Scheduling theory, which is usually used to determine the sequencing of operations in such settings as transportation and manufacturing, provides normative answers to such a question. The authors introduce the concepts and terminology of scheduling theory and show how these can be identified with aspects of human operator behavior. Scheduling theory can provide a systematic conceptual framework for planning research on behavior in complex human-machine settings, both in and beyond laboratory contexts. It can be used to discover optimal or satisficing strategies and to provide norms against which to measure the quality of strategic decision making and performance in complex systems. The use of scheduling theory is one example of the many well-developed quantitative models available in operations research that are applicable to the analysis of behavior, well beyond the discrete trials paradigm that often characterizes human factors laboratory research.

Influence of flooring on standing fatigue

Abstract: This study investigated effects of flooring on perceived tiredness, fatigue, and discomfort for workers required to stand while performing their jobs. Eight flooring conditions of varying thickness and stiffness (including one shoe insert) were evaluated by workers who answered a questionnaire. Questions were asked regarding whole-body tiredness. leg fatigue. and discomfort. Flooring had a significant effect on workers' perception. In general softer materials caused less perceived tiredness; however, one extremely soft floor resulted in higher ratings of tiredness. Similar results were found for material thickness. The shoe insert condition showed low tiredness ratings as compared with most floors, including one made of the same material. The discomfort ratings indicated that harder flooring materials caused greater discomfort. Discomfort of the lower extremities tended to decrease as distance from the floor increased. Low back discomfort was found for hard flooring surfaces.

Increasing the usability of interactive voice response systems: research and guidelines for phone-based interfaces

Abstract: Thousands of applications-from airline reservations to zoo schedules-use phonebased interfaces to provide information to callers and to request input. The dramatic increase in the number of these applications has led to wide variability in the quality of the interface design. Most users have no choice but to grudgingly accept these systems; experience with poorly designed phone-based interfaces has led to widespread dissatisfaction. We believe that the lack of published guidelines for interface design for these systems contributes to the variability in quality and thus to user antipathy. In this paper we propose guidelines for construction of phone-based interfaces to interactive voice response systems. These guidelines are a compilation of information from the best of current practices, empirical research where available, and the wisdom of the industry. We see this collection as a starting point for further discussion and standardization that will ultimately lead to optimally usable interactive voice res...