bluuebunny/crossref_metadata_2025 huggingface dataset:
A Closed-Loop Causal Model of Workload Based on a Comparison of Fuzzy and Crisp Mesaurement Techniques
Authors: Moray Neville , King Barbara , Turksen Burhan , Waterton Keith
Published: July 2017

Fuzzy and crisp measurements of workload are compared for a tracking task that varied in bandwidth and order of control. Fuzzy measures are as powerful as crisp measures, and can under certain conditions give extra insights into workload causality. Both methods suggest that workload arises in a system in which effort, performance, difficulty, and task variables are linked in a closed loop. Marked individual differences were found. Future work on the fuzzy measurement of workload is justified.
Methodological Considerations for the Assessment of Traffic Safety Trends and Interventions
Authors: Stanislaw Harold
Published: July 2017

Long-term trends in traffic safety are usually modeled by regressing the fatal accident rate on time. Safety interventions can then be assessed by evaluating their impact relative to these baseline trends. However, this approach confounds the accident rate with the fatality rate and introduces a number of statistical problems. Methods for avoiding these problems are illustrated by modeling California traffic safety data for the years 1939 to 1973. These models reveal a substantial reduction in the proportion of accidents involving fatalities. No such reduction is evident in accident frequency, after changes in vehicle mix and the driver age distribution are taken into account.
Perspective Traffic Display Format and Airline Pilot Traffic Avoidance
Authors: Ellis Stephen R. , Mcgreevy Michael W. , Hitchcock Robert J.
Published: July 2017

Part-task experiments have examined perspective projections of cockpit displays of traffic information as a means of presenting aircraft separation information to airline pilots. Ten airline pilots served as subjects in an experiment comparing the perspective projection with plan-view projections of the same air traffic situations. The pilots' task was to monitor the traffic display in order to decide if an avoidance maneuver was needed. Pilots took more time to select avoidance maneuvers with a conventional plan-view display than with an experimental perspective display. In contrast to previous results, if the pilots selected a maneuver with the perspective display, they were more likely to choose one with a vertical component. Tabulation of the outcomes of their initial avoidance decisions with both perspective and plan-view displays showed that they were more likely to achieve required separation with maneuvers chosen with the aid of perspective displays.
Automatic and Control Processing Approach to Interpreting Vigilance Performance: A Review and Reevaluation
Authors: Fisk Arthur D. , Scerbo Mark W.
Published: July 2017

The present paper discusses vigilance phenomena in terms of the automatic/control processing theory (Schneider and Shiffrin, 1977) of attention and human information processing. Fisk and Schneider (1981) interpreted vigilance decrements within the automatic/control process framework and discussed system design implications as well as training methods for vigilance environments. Recent results concerning the effects of various stressors on automatic and control processes are presented. Taken as a whole, these results from vigilance, alcohol intoxication, heat stress, and mental workload experiments highlight why, when addressing sustained attention issues, it is critical to understand the mode of information processing (i.e., automatic/control) available to perform the task.
Diurnal Variation, Task Characteristics, and Vigilance Performance
Authors: Craig A. , Davies D. R. , Matthews G.
Published: July 2017

Three experiments consider the effects of several task features along with the time of day when vigilance was tested. The first experiment found that detections on the Bakan task depended on event rate and signal frequency and that the adverse effects of lowering signal frequency were more marked in the afternoon than in the morning. The second experiment found that the typical sensitivity decrement on a brief, rapidly paced successive discrimination task occurred earlier when the stimuli were degraded—especially in the early evening as compared with the morning—and that a riskier criterion placement was adopted in the evening. The third experiment used an unpaced simultaneous discrimination task with equiprobable stimulus events. Efficiency was not stable but declined as time passed, while speed increased. These changes tended to be more apparent in the afternoon, and perceptual efficiency seemed genuinely lower than in the morning. The implications for interpretations of vigilance and time-or-day effects are discussed.
Human-Computer Monitoring
Authors: Parasuraman Raja
Published: July 2017

Attentional factors can influence user interaction with automated and semiautomated monitoring systems. Three aspects of human-computer monitoring are considered in this paper: (1) vigilance effects in complex monitoring tasks, (2) factors influencing optimal combination of human and computer monitors, and (3) effects of increased automation on the relationship between mental workload and vigilance. Results of laboratory and simulation studies suggest that vigilance effects can limit performance in complex monitoring tasks. Performance deficits may occur because of either vigilance decrement over time or sustained low levels of vigilance. However, the specific factors that influence sustained performance with complex displays have not been identified precisely. Computer assistance to enhance performance is feasible but may not be effective in all cases. Performance gain is dependent on several factors, including the decision rule for combining human and computer decisions and the level of mental workload imposed on the human monitor. Finally, in assessing the impact of increased automation the beneficial effects on mental workload have to be traded off against possible adverse effects on vigilance. The implications of these factors for the design of automated monitoring systems are discussed.
Factors Affecting the Readability of Moving Text on a Computer Display
Authors: Chen Hsuan-Chih , Tsoi Kam-Cheong
Published: July 2017

In two experiments text was horizontally advanced in discrete jumps of one or several characters at a time along a single line on a computer-controlled screen (i.e., the leading text display format). Experiment 1 showed that when the display rate was relatively fast or when the window size was relatively small, jump lengths of five character spaces resulted in higher comprehension than did one- or nine-character jump conditions. In Experiment 2 the text display rate was under either experimenter or subject control; results showed that permitting the subject to control the rate of text presentation did not improve reading comprehension. However, when the rate of text presentation was under the control of the subject, reading efficiency (Rate x Comprehension) improved with practice.
Hand Steadiness: Effects of Sex, Menstrual Phase, Oral Contraceptives, Practice, and Handgun Weight
Authors: Hudgens Gerald A. , Fatkin Linda T. , Billingsley Patricia A. , Mazurczak Joseph
Published: July 2017

Two experiments were conducted in which men, normally cycling women, and women on menstrual cycles generated by the regular ingestion of oral contraceptives were compared for hand steadiness. In Experiment 1 subjects were tested on a standard laboratory hand-steadiness task. In Experiment 2 subjects were similarly tested while holding handguns of varying weights. In both experiments normally cycling women were steadiest, women on oral contraceptives were least steady, and men were intermediate. The relative differences lasted at least eight sessions. In addition, normally cycling women were found to experience a large decrement in performance during the premenstrual phase of their cycles. It was concluded that the men and women differ in hand steadiness and that the difference is repeatable, persistent, and at least somewhat generalizable. Oral contraceptive use and menstrual events must be taken into account in considering steadiness in women and should be considered more generally in performance assessment by psychological and human factors researchers.
Postural Adaptations to a Sloping Chair and Work Surface
Authors: Bridger Robert S.
Published: July 2017

Sitting postures were observed in four different work spaces that were designed using combinations of a conventional chair, a forward-sloping chair, and a horizontal or sloping work surface. Subjects sat at each of the work spaces while a lateral view of posture was recorded using a video camera. The slumped posture typically reported in the literature was observed when the conventional work space was used. When the sloping chair was used, postures exhibited less trunk flexion. When the sloping work surface was used, less neck flexion and a more upright trunk were observed. Although the differences between the work spaces were small, the sloping furniture was perceived to be more comfortable than the conventional furniture.
An Experimental Study of Chinese Information Displays on VDTs
Authors: Hwang Sheue-Ling , Wang Min-Yang , Her Chih-Chin
Published: July 2017

An experiment was designed with four independent variables for Chinese information displays on video display terminals (VDTs): (1) character spacing, (2) display control (scrolling or paging), (3) scrolling speed, and (4) display format (horizontal or vertical). The dependent variables were visual fatigue and performance measures including fault detection, reading speed, and comprehension level. Sixty university students participated in the experiment and read an BOOO-word article on the VDT. The results revealed that some interaction and main effects were significant, and recommendations were made for the design of Chinese information displays that could be applied to office automation systems.
Multiple Resources for Processing and Storage in Short-Term Working Memory
Authors: Klapp Stuart T. , Netick Allan
Published: July 2017

A frequent assumption in cognitive psychology is that performance in decision making and planning is severely restricted by the limited capacity of short-term working memory. Many predictions of this theory have not been supported, possibly because working memory may be composed of multiple resources rather than a single resource. The present experiments study two tasks, both involving memory for digits. Although these tasks can employ the same modality for input and for responding, they appear to differ in their demands for working memory resources. Specifically, the tasks appear to differ in resources required for processing at input, and they also differ in resources in the sense of storage capacity. The results support a version of multiple-resource theory applied to working memory in which resource composition depends on internal mediators even when stimulus and response modality are held constant.
Comprehension Aids for On-Line Reading of Expository Text
Authors: Lachman Roy
Published: July 2017

A chapter of expository text was presented on a CRT with optional “windowing” of definitions of selected words varying in relevance to each screen's main ideas. A test treatment was interposed to influence reading strategies. Dependent variables included text reading time, frequency of definition “calls,” definition reading rates, and scores on a final comprehension test. Results indicate that a technical chapter can be read from a CRT with appreciable content retention. Subjects accessed 80% of available definitions, but those able to “call” content-relevant definitions increased their frequency of definition “calls.” Definition reading rate diminished; comprehension and processing time increased only for subjects accessing the theoretically relevant definitions. The results suggest how the use of definitions enhances the comprehension of on-line training manuals, texts, and help screens. “Callable” definitions need not include all low-frequency technical concepts but only those relevant to reductive main ideas.
Modeling the Cognitive Content of Displays
Authors: Chechile Richard A. , Eggleston Robert G. , Fleischman Rebecca N. , Sasseville Ann Marie
Published: July 2017

An approach for measuring the cognitive complexity of visual displays is discussed and applied to a dynamic display of avionic information. A semantic network formalism is used to model two interrelated knowledge systems, world knowledge and display knowledge. The information the operator receives during training about the general display format characteristics and the task requirements, along with other previously stored information, constitutes world knowledge. The semantic content of a particular configuration of information encountered during task performance constitutes display knowledge. Four orthogonal predictor measures of cognitive complexity were derived from the networks. In an experiment three of the orthogonal predictors were significantly correlated with task performance. After averaging across operators, the three significant predictors accounted for 99% of the variation of display effectiveness. Results indicate that a model of cognitive complexity based on a semantic network formalism may provide a useful technique for quantitatively evaluating the quality of competing display format concepts.
Narcosis Has Additive Rather Than Interactive Effects on Discrimination Reaction Time
Authors: Fowler Barry , Mitchell Ian , Bhatia Mini , Porlier Gerald
Published: July 2017

A central feature of the impairment in performance produced by inert gas narcosis, which poses a threat to divers breathing compressed air, is a slowing of reaction time (RT). To investigate the locus of this slowing, the effects of 35% nitrous oxide on Crossman's confusion function were determined using line-length and weight discrimination tasks, with accuracy held constant. For both tasks narcosis slowed RT by increasing the intercept rather than the slope of Crossman's function. These results are interpreted in terms of additive factors method logic as being consistent with the predictions of the slowed processing model that has been proposed to account for the effects of narcosis on human performance.
Prediction of Head Movement Time Using Fitts’ Law
Authors: Andres Robert O. , Hartung Kenny J.
Published: July 2017

Fitts’ movement time prediction equation has been applied and manipulated in analyzing movements of the upper and lower extremities in healthy populations. One common job modification for physically challenged workers is the use of a head or chin stick to depress keys on a keyboard, making use of head movements when movements of the extremities are problematic. The purpose of this research was to assess the applicability of Fitts’ law for the prediction of head movement time. Movement was restricted in healthy subjects by limiting body movement below the neck. Subjects were asked to reciprocally move a chin stylus between targets of various widths and separations. The present study found that Fitts’ law was a robust predictor of head movement time in healthy, college-age males using a chin stylus. Although small within-subjects trends were noted, there were no significant learning effects from Session 1 to Session 2. The mean information-processing rate for the experimental head movement was 7 bits/s, much less than that reported for extremities. These results can provide rehabilitation and industrial engineers valuable insight into the added demands of jobs designed to use repetitive head movements.
The Effects of a Simulated Head-Up Display Speedometer on Perceptual Task Performance
Authors: Sojourner Russell J. , Antin Jonathan F.
Published: July 2017

This study compared the effects of simulated head-up display (HUD) and dashboard-mounted digital speedometers on key perceptual driving tasks in a simulated driving environment. Subjects were 20 male and female volunteers ranging in age from 19 to 51 years. A videotape, taken from the driver's perspective, of a car traveling along a memorized route served as the test scene. While viewing the test scene subjects performed tasks related to navigation, speed monitoring, and salient cue detection. The simulated HUD speedometer produced generally superior performance on the experimental tasks; most important, it enabled subjects to respond significantly more quickly to the salient cues. Implications for the effects of HUDs on automobile safety are discussed.
Physiological Capacities of Individuals with Cerebral Palsy
Authors: Fernandez Jeffrey E. , Pitetti Kenneth H. , Betzen Maria T.
Published: July 2017

The physical work capacity (PWC) and the physiological response to simulated tasks of nine ambulatory individuals with cerebral palsy (CP) were studied. Energy demand for each work task was determined by percentage of PWC (%PWC). Results demonstrated significant differences in energy demand attributed to frequency and mode of lift regardless of gender. No significant difference for energy demand, however, was seen for load lifted. The %PWC for several tasks was near or above the accepted limit for an eight-hour workday, suggesting that the subjects were performing close to their physical limits or higher and would possibly experience fatigue before the eight-hour workday ended. The results also indicated that the PWC of subjects in this study was inferior to that of their nondisabled peers.
Sensory Alternation and Vigilance Performance: The Role of Pathway Inhibition
Authors: Galinsky Traci L. , Warm Joel S. , Dember William N. , Weiler Ernest M. , Scerbo Mark W.
Published: July 2017

Posner's theory of pathway inhibition leads to the expectation that stimulus heterogeneity should attenuate the event rate effect and the decrement function in sustained attention. These predictions were tested through a sensory alternation procedure in which stimulation was shuttled between the auditory and visual modalities. Subjects detected slight reductions in the duration of recurrent flashes of light or bursts of white noise at two event rates (5 and 40 events/min) during a 50-min vigil. Consistent with the model, sensory alternation eliminated the event rate effect. It did not, however, moderate the decrement function. Although pathway inhibition can account for the effects of event rate, other factors are probably responsible for the vigilance decrement.
A Three-Dimensional Motion Model of Loads on the Lumbar Spine: I. Model Structure
Authors: Marras William S. , Sommerich Carolyn M.
Published: July 2017

Traditionally most biomechanical models that are used to estimate the loading experienced by the spine during work focus on static, two-dimensional representations of the work. However, most work tasks impose loads on the lumbar spine under dynamic, three-dimensional conditions. The objective of this study was to describe the structure and logic of a model that is capable of producing estimates of spine loading under three-dimensional motion conditions. This model is intended for use primarily under laboratory conditions. The model was designed initially for workplace simulation in which the trunk is moving under symmetric and asymmetric constant velocity lifting conditions. Future embellishments may enable the model to be used under free dynamic conditions. The model predicts lumbar spine compression, shear, and torsional forces as well as trunk torque production continuously throughout the exertion. This information may be compared with spine tolerance limits so that the risk of causing a vertebral end-plate microfracture by workplace requirements could be determined.
A Methodology for Quantifying Expert System Usability
Authors: Mitta Deborah A.
Published: July 2017

A methodology for quantifying expert system usability is presented. Usability is considered from a designer's perspective: the designer must ultimately address any design Issues that may affect usability. A linear multivariate function for measuring usability is described. The function's independent variables represent user perceptions and performance. In an example a function of this form is developed and used to assign a usability score to a given expert system. The usefulness of the usability function as a design tool is also investigated.
Recombination of Automatic Processing components: The Effects of Transfer, Reversal, and Conflict Situations
Authors: Fisk Arthur D. , Lee Mark D. , Rogers Wendy A.
Published: July 2017

This research was conducted to evaluate the effects of compatible and incompatible automatic processes on performance. Subjects were trained for 8400 trials of consistent mapping practice in a semantic category visual search task and then transferred for 2352 trials to conditions that utilized the trained component processes in various ways. Results indicate that if the components were reused in a compatible fashion (target and distractor transfer), there was positive transfer. Target and distractor reversal resulted in equivalent and severe performance disruption that persisted for the entire retraining period. Target conflict produced disruption equivalent to the reversal conditions. Distractor conflict resulted in less initial disruption, which dissipated before the end of the retraining period. The results are discussed in terms of agreement with strength-theoretic views of visual search and in terms of practical training and retraining issues.
The Older Driver
Authors: Waller Patricia F.
Published: July 2017

Older drivers constitute the most rapidly growing segment of the driving population in number of drivers licensed, miles driven, and proportion of the driving population. Yet the highway transportation system has not been designed for these drivers. This lack of fit is reflected in the accelerating rate of crashes per mile driven experienced by older drivers beginning around age 55. Furthermore, older persons are more vulnerable to injury once a crash occurs and as a group experience a higher fatality rate. The increasing proportion of our population consisting of older persons, in conjunction with a relative decrease in the young adult population, underscores the need for research to develop a greater understanding of the needs and capabilities of this age group and to develop system improvements that will enable as many older persons as possible to continue to meet their own transportation needs safely.
Visual Requirements for Safety and Mobility of Older Drivers
Authors: Shinar David , Schieber Frank
Published: July 2017

Efforts to assess visual deterioration with increasing age, coupled with new mechanisms proposed to limit the exposure of visually impaired drivers to driving risks, have emerged in response to the increase in older drivers. Visual functions discussed in this context include static acuity (photopic, mesopic, and in the presence of glare), dynamic visual acuity, visual field, contrast sensitivity, and motion perception. Exposure control mechanisms discussed include alternative periodic vision testing strategies, visual training, and environmental and vehicular modifications to accommodate the older driver. Finally, relevant research needs are addressed.
Consistency of Human-Computer Interface Design: Quantification and Validation
Authors: Tanaka Toshiaki , Eberts Ray E. , Salvendy Gavriel
Published: July 2017

Consistency in human-computer interaction tasks is usually considered in a transfer paradigm in which the higher the similarity between two tasks, the higher the transfer and consistency. In a different paradigm, when tasks are performed in alternating sequences, similarity of tasks means that the mapping of interface methods or rules to overall task goals will be varied. A neural network simulation demonstrated that the same two tasks could be considered consistent in a transfer paradigm but have low consistency when they are alternated. A model called text-editing method (TEM) was developed to quantify consistency between two tasks based upon replacement, insertion, or deletion of methods. Two experiments tested the predictions of the quantitative analyses of consistency for alternating tasks. The results confirmed that similarities of two tasks and, thus, variability in the mapping of methods to overall task goals could have a detrimental effect on performance when the two tasks were performed in an alternating sequence.
Using the Subjective Workload Dominance (SWORD) Technique for Projective Workload Assessment
Authors: Vidullch Michael A. , Ward G. Frederic , Schueren James
Published: July 2017

The present study examined the utility of the Subjective Workload Dominance (SWORD) technique as a projective workload tool. Two groups predicted the workload associated with using six possible head-up display (HUD) formats. One group contained college students inexperienced with HUDs, and the second group contained operational F-16 pilots who commonly used HUD displays but were familiar with only one format. The projective ratings from these groups were correlated with retrospective ratings from a group of operational F-16 pilots that had experienced all six formats in a simulator study. The correlation between the projective and retrospective groups of pilots was highly positive, and both groups′ ratings correlated positively with the simulator study performance. In contrast, the student ratings were not significantly correlated with the ratings from either of the other groups, nor was performance. The results support the utility of the SWORD technique as a projective tool, provided a group of subject matter experts is available to make the required judgments.
A Controlled Investigation of In-Field Attenuation Performance of Selected Insert, Earmuff, and Canal Cap Hearing Protectors
Authors: Park Min-Yong , Casali John G.
Published: July 2017

A field study assessed the actual spectral noise attenuation achieved by 40 industrial workers wearing four different hearing protection devices (HPDs) while on the job. The effect of two different HPD fitting procedures (subject fit vs. trained fit) on attenuation performance over two three-week periods of protector use was determined. Subjects were retrieved from their workplaces without prior knowledge of when they were to be tested and were not permitted to readjust the fit of their HPDs. Attenuation data were then collected using psychophysical procedures testing real ear attenuation at threshold. Statistical analyses indicated that the earplugs′ attenuation significantly improved when training for proper fitting was used, whereas the earmuff and the ear canal cap were relatively insensitive to the training effect. The training was most effective for a slow-recovery foam plug over the three-week period. Results confirmed that laboratory protocols designed to simulate workplace influences on attenuation may not be relied on to yield reasonable estimates of field protection performance of HPDs, particularly for earplugs; however, the laboratory results were much better predictors of field protection for the earmuff. This study also demonstrated that the labeled manufacturers′ noise reduction ratings (NRRs) substantially overestimated the actual field attenuation performance.
Brake Reaction Time to Center High-Mounted Stop Lamps on Vans and Trucks
Authors: McKnight A. James , Shinar David
Published: July 2017

Center high-mounted stop lamps (CHMSLs) have been standard equipment on passenger cars in the United States since September 1, 1985. This study investigated the potential benefit of extending the CHMSL to heavier vehicles by measuring the savings in brake reaction time. In an experimental field study of over 1000 trials, CHMSLs were installed on a pickup truck, a full truck, a cargo van, and a minivan. The brake reaction times of drivers following these vehicles with and without CHMSLs were measured. Activation of the CHMSL in tandem with the standard brake lights had a small but statistically significant effect on the brake response time of the drivers in following vehicles. No statistically significant differences in CHMSL effect were observed among the four test vehicles. This effect was similar in magnitude to the effect of a CHMSL in a passenger vehicle when measured under the same conditions.
Testing the Effect of Road Traffic Signs′ Informational Value on Driver Behavior
Authors: Fisher James
Published: July 2017

Measurement of the informational value of road traffic signs by questioning drivers at experimental roadblocks suggests that memory for signs is typically poor. This paper reports a study designed to assess the links among memory for road signs, driver behavior, and control adjustment action. Findings indicate that the effectiveness of road signs should be assessed in terms of their ability to sensitize the driver to hazards, rather than in terms of recall accuracy, and point to inconsistencies between drivers′ verbal recall and vehicle control behavior which are not readily apparent from roadblock research.
Developing Quantitative Guidelines Using Integrated Data from Sequential Experiments
Authors: Williges Robert C. , Williges Beverly H. , Han Sung H.
Published: July 2017

The results of four experiments were integrated using empirical models and data bridging. These models can be used in the design of telephone-based information systems as quantitative guidelines. Ten independent variables including environmental, hardware, dialogue, and user factors were considered in four related studies. Three dependent variables (total search time, user-added keypresses, and message transcription accuracy) were evaluated in each separate study. Multiple linear regression was used to generate an integrated second-order empirical model for each of the three dependent variables. Overall, the use of integrated empirical models offers several advantages. First, both qualitative and quantitative design guidelines can be generated. Second, a broad base for generalization across several studies is provided. Third, interface design trade-offs are possible.
Test and Evaluation Metrics for Use in Sustained Acceleration Research
Authors: Mccloskey Kathy A. , Tripp Lloyd D. , Chelette Tamara L. , Popper Stephen E.
Published: July 2017

This paper reviews three models that historically have been used to explain and describe the effects of greater than I g forces on humans: the hydrostatic column model, the blood oxygen saturation model, and the neurological model. We outline metrics that relate to each of the three models and offer a unified model based on integration of those models. The match between ground-based centrifuges and aircraft is examined, as is transfer of results from the centrifuge to the aircraft. Last, we examine the feasibility of using physiological, subjective, and performance metrics in the aircraft.
Selecting Performance Measures: "Objective" versus "Subjective" Measurement
Authors: Muckler Frederick A. , Seven Sally A.
Published: July 2017

The distinction between "objective" and "subjective" measurement is neither meaningful nor useful in human performance studies. All measurement in science and technology is necessarily filled with subjective elements, whether in selecting measures or in collecting, analyzing, or interpreting data. Empirical examples taken from several domains related to human factors show instances in which self-report (subjective) measures may be essential. Amodel process is suggested for selecting performance measures.
Optimal Performance Engineering: Good, Better, Best
Authors: Fisher Donald L.
Published: July 2017

A quiet revolution is in progress in the field of human factors. This revolution is broadly based, finding a home not only in such traditional areas as workplace layout and industrial ergonomics but also in more recent areas, such as humancomputer interaction and cognitive engineering. The revolution affects the way research questions are posed and the types of answers that are offered. No longer is a good or better solution adequate. Rather, the focus has turned to the best or optimal solution. In this article the research in optimal performance engineering is selectively reviewed. It is argued that increasing the number and range of attempts to engineer optimal performance will lead not only to safer and more efficient designs but also to an increase over the long run in the applicability and accessibility of laboratory research.
Effects of Stereoscopic and Rotational Displays in a Three-Dimensional Path- Tracing Task
Authors: Sollenberger Randy L. , Milgram Paul
Published: July 2017

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.
Pistol Grip Power Tool Handle and Trigger Size Effects on Grip Exertions and Operator Preference
Authors: Oh Seoungyeon , Radwin Robert G.
Published: July 2017

Finger and palmar forces were measured during actual pneumatic nutrunner operation using a strain gauge dynamometer. Eighteen student subjects were assigned to one of three categories based on hand length. Two triggers and four handle spans were presented randomly. Handle span affected maximal and submaximal grip force. Asspan increased from 4 cm to 7 cm, average peak finger force increased 24%, peak palmar force increased 22%, and average finger and palmar tool-holding forces increased 20%. When an extended trigger was used, average peak finger force decreased 9%, peak palmar force decreased 8%, finger tool-holding force decreased 65%, and palmar tool-holding force decreased 48%. Hand size affected grip strength (MVC),grip force, and exertion level (force/MVC). Holding exertion level was maximum for large-handed subjects using a 4-cm handle and for small-handed subjects using a 7-cm handle. Subjective handle span preference increased as hand size increased. A similar experiment was performed using 11 factory workers.
Head-Up Auditory Displays for Traffic Collision Avoidance System Advisories: A Preliminary Investigation
Authors: Begault Durand R.
Published: July 2017

The advantage of a head-up auditory display was evaluated in a preliminary experiment designed to measure and compare the acquisition time for capturing visual targets under two auditory conditions: standard one-earpiece presentation and two-earpiece three-dimensional (3D) audio presentation. Twelve commercial airline crews were tested under full mission simulation conditions at the NASA Ames Man-Vehicle Systems Research Facility advanced concepts flight simulator. Scenario software generated visual targets corresponding to aircraft that would activate a traffic collision avoidance system (TCAS) aural advisory; the spatial auditory position was linked to the visual position with 3D audio presentation. Results showed that crew members using a 3D auditory display acquired targets approximately 2.2 s faster than did crew members who used one-earpiece headsets, but there was no significant difference in the number of targets acquired.
Physical Fatigue in High and Very High Frequency Manual Materials Handling: Perceived Exertion and Physiological Indicators
Authors: Mital Anil , Foononi-Fard Hamid , Brown Max L.
Published: July 2017

This paper presents the results of a preliminary laboratory study undertaken to determine the perceived exertion and physiological responses of highly trained and experienced workers to high (up to 16 repetitions/min) and very high frequency (above 16 repetitions/min) manual lifting, lowering, and carrying/turning tasks. The results indicate that workers engaged in such highly repetitive and physically demanding tasks may operate at psychophysical workloads that may clearly be considered physically fatiguing and unacceptable according to the current physiological design criteria. In this study subjects performing lifting and lowering tasks, on the average, operated at 57% and 52% of their uphill treadmill aerobic capacity, respectively. For carrying and turning tasks, the average metabolic energy expenditure rate corresponded to 43% of subjects' aerobic capacity. The overall heart rates of the study subjects were 155 beats per minute (bpm) for lifting, 144 bpm for lowering, and 142 bpm for carrying and turning. These physiological responses, when compared with recommended physiological design criteria, are excessively high. The ratings of perceived exertion (RPE) for the shoulder, back, and whole body were highest for lifting (range, 10.20-15.50) and least for carrying and turning (range, 10.30-13.40; carrying and turning activities also included RPE of arms). Generally workers perceived the associated physical exertions as acceptable.
Work Practices, Fatigue, and Nuclear Power Plant Safety Performance
Authors: Baker Kathryn , Olson Jon , Morisseau Dolores
Published: July 2017

This paper focuses on work practices that may contribute to fatigue-induced performance decrements in the commercial nuclear power industry. Specifically, the amount of overtime worked by operations, technical, and maintenance personnel and the 12-h operator shift schedule are studied. Although overtime for all three job categories was fairly high at a number of plants, the analyses detected a clear statistical relationship only between operations overtime and plant safety performance. The results for the 12-h operator shift schedule were ambiguous. Although the 12-h operator shift schedule was correlated with operator error, it was not significantly related to the other five safety indicators. This research suggests that at least one of the existing work practices---the amount of operator overtime worked at some plants---represents a safety concern in this industry; however, further research is required before any definitive conclusions can be drawn.
Extended Workdays in an Underground Mine: A Work Performance Analysis
Authors: Duchon James C. , Keran Christopher M. , Smith Thomas J.
Published: July 2017

Many companies in different industrial sectors are exploring alternative work schedules to deal with diverse problems associated with shiftwork. The use of extended workday schedules (regular shift lengths exceeding 8 h with compressed workweeks) is attracting growing interest in many industries that use continuous operations. To address concerns regarding possible fatigue effects on safety and work performance associated with such schedules, the U.S. Bureau of Mines conducted a two-phase study at an underground metal mine in western Canada. Data were collected before and after a group of workers employed at the mine changed from an 8- to a 12-h schedule. Results indicate nearly unanimous acceptance and improved sleep quality associated with the new schedule. In general, fatigue-sensitive behavioral and physiological performance measures show either no change or improvement with 12-h shifts. We conclude that the extended workday schedule should be retained but periodically reevaluated.
Fatigue and the Shiftworker: Firefighters Working on a Rotating Shift Schedule
Authors: Paley Michael J. , Tepas Donald I.
Published: July 2017

Fatigue has often been viewed as a simple variable that is positively correlated with time on task in the workplace and is produced mainly by physical activity. However, shiftwork researchers have demonstrated time-of-day differences for variables including sleepiness and mood, thereby challenging this notion of fatigue. Using a within-subjects design, the present study advances this research by searching for differences in time-of-day interactions in firefighters' sleep length, sleepiness, and mood ratings as a function of shift. We examined reductions in sleep length associated with shiftwork and used sleepiness and mood scales to assess the effects of these reductions. Participants completed surveys throughout a complete cycle of their shift schedule. The study showed that firefighters working on a rotating S-h shift schedule will sleep less and will report lower positive mood scores, higher negative mood scores, and greater sleepiness ratings on the night shift. Additionally, it was shown that over the course of a shift (two weeks), firefighters were unable to adapt to changes in their sleep schedule. Finally, the significant interactions that were observed challenge the historical, singular notion of fatigue.
Subjective Fatigue of C-141 Aircrews during Operation Desert Storm
Authors: Neville Kelly J. , Bisson Roger U. , French Jonathan , Boll Patricia A. , Storm William F.
Published: July 2017

Airlift crews were exposed to extended work periods, reduced sleep periods, night work, and circadian dysrhythmia caused by shift work and time-zone crossings during Operations Desert Shield and Desert Storm. This research reveals the extent to which severe subjective fatigue was experienced by the crews during Operation Desert Storm. In addition, through the evaluation of long-term and short-term work and sleep histories, this research shows that recent sleep and flight histories are correlated with high fatigue levels. Furthermore, we found a tendency for fatigue to correspond with pilot error. We recommend that the training of personnel involved in long-duration operations include fatigue management strategies and, further, that work policies and environments be designed to take into account the importance of regular and restorative sleep when unusual duty hours are required.
Sample Sizes for Usability Studies: Additional Considerations
Authors: Lewis James R.
Published: July 2017

Recently, Virzi (1992) presented data that support three claims regarding sample sizes for usability studies: (1) observing four or five participants will allow a usability practitioner to discover 80% of a product's usability problems, (2) observing additional participants will reveal fewer and fewer new usability problems, and (3) more severe usability problems are easier to detect with the first few participants. Results from an independent usability study clearly support the second claim, partially support the first, but fail to support the third. Problem discovery shows diminishing returns as a function of sample size. Observing four to five participants will uncover about 80% of a product's usability problems as long as the average likelihood of problem detection ranges between 0.32 and 0.42, as in Virzi. If the average likelihood of problem detection is lower, then a practitioner will need to observe more than five participants to discover 80% of the problems. Using behavioral categories for problem severity (or impact), these data showed no correlation between problem severity (impact) and rate of discovery. The data provided evidence that the binomial probability formula may provide a good model for predicting problem discovery curves, given an estimate of the average likelihood of problem detection. Finally, data from economic simulations that estimated return on investment (ROI) under a variety of settings showed that only the average likelihood of problem detection strongly influenced the range of sample sizes for maximum ROI.
Transfer of Skill from a Computer Game Trainer to Flight
Authors: Gopher Daniel , Well Maya , Bareket Tal
Published: July 2017

An experimental study was conducted to test the transfer of skills from a complex computer game to the flight performance of cadets in the Israeli Air Force flight school. The context relevance of the game to flight was argued on the basis of a skill-oriented task analysis, using the framework provided by contemporary models of the human processing system. The influence of two embedded training strategies was compared, one focusing on the specific skills involved in performing the game, the other designed to improve the general ability of trainees to cope with the high processing and response demands of the flight task and teach better strategies of attention control. Efficient control and management of attention under high task load are argued to be skills that can improve with proper training and generalize to new situations. Flight performance scores of two groups of cadets who received 10 h of training in the computer game were compared with those of a matched group without game experience. Both game groups performed significantly better than the no-game group in the subsequent test flights. The results are discussed with reference to the theoretical framework within which the context relevance of the game was supported. Also considered are the effects of the different training schedules and the significance of the data to the study of attention control. The game has now been incorporated into the regular training program of the Air Force.
Psychophysiological Measures of Workload during Continuous Manual Performance
Authors: Backs Richard W. , Ryan Arthur M. , Wilson Glenn F.
Published: July 2017

Twelve subjects (six female) participated in an experiment designed to separate the effects of perceptual/central and physical demands on psychophysiological measures of peripheral nervous system activity. The difficulty of a single-axis continuous manual tracking task was varied in two ways: order of control was manipulated to vary perceptual/central processing demand, and disturbance amplitude was manipulated to vary physical demand. Physiological measures were sensitive to the imposition of a task and were more sensitive to physical than to perceptual/central demands. A principal components analysis identified five factors (three of them physiological) that accounted for 83.1% of the observed variance. Perceptual/central processing demands specifically affected the component identified with sympathetic cardiovascular control, whereas physical demands were reflected in the component identified with parasympathetic cardiovascular control. This finding suggests that dissociations observed among cardiovascular measures in manual performance tasks are attributable to differential activation of the autonomic control systems.
Young Children's Ability to Climb Fences
Authors: Rabinovich Beth A. , Lerner Neil D. , Huey Richard W.
Published: July 2017

Three studies were performed to evaluate the fence-climbing abilities of children who are in the high-risk age group for drowning in residential pools. Study 1 examined the ability of children in the age range of 24 to 54 months to climb commonly used fences (common chain link, small chain link, picket, iron, and stockade) at a 4-ft (1.22-m) height. Study 2 examined children's abilities to climb fences retrofitted with features that would potentially make them more difficult to climb. Study 3 examined children's abilities to climb 5-ft (1.52-m) fences. Results of the three studies show that the common chain-link fence is easy to climb even by two-year-old toddlers. Other fence types offered more effective barriers, especially for younger children.