bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Extended Practice on Dual-Task Tracking Performance
Authors: Damos Diane L. , Bittner Alvah C. , Kennedy Robert S. , Harbeson Mary M.
Published: July 2017

A critical tracking task combination was examined for inclusion in an exotic environment test battery. Performance increased throughout 15 testing sessions despite the subjects' extensive prior tracking experience. However, consistent individual differences occurred only after Session 10. The implications of these results for research on exotic environments and timesharing abilities are discussed.
Evaluation of Maximal and Submaximal Static Muscle Exertions
Authors: Kroemer K. H. E. , Marras William S.
Published: July 2017

A model of the regulation of muscle strength exertion is proposed. Based on the model, methods are discussed to assess whether a subject exerts maximal or submaximal efforts. Results with 40 subjects indicate that a simple technique may be developed to judge if a subject is following instructions to exert a maximal contraction in a routine test of voluntary muscle strength.
Driver/Vehicle Steering Response Latencies
Authors: Summala Heikki
Published: July 2017

A steering maneuver was induced among unalerted drivers by the sudden opening of the door of a car parked near the path of travel. Lateral displacement of 1326 cars was measured unobtrusively. When plotted as a function of the time available for it, the averaged lateral displacement started at a latency of about 1.5 s, reached its halfway point at 2.5 s and its maximum at somewhat less than 4 s. This steering-response function was similar whether measured close to the parked car or 15 m in front of it, and it was independent of the cars' prior speed or lateral position. On the basis of these and consistent earlier results from related experiments, it was recommended that, for safe operation, at least 3 s should be reserved for drivers to respond, by steering, to changes in the road environment.
Issues in Human Reliability
Authors: Adams Jack A.
Published: July 2017

The correct premise of the topic of human reliability is that system personnel fail in their responding just as equipment does, and so they must be considered along with the equipment in the specification of system reliability. The goal of human reliability efforts as they are presently pursued is to find measures of the reliability of human performance that are expressed in the same terms as measures of equipment reliability and can be combined with them to produce system reliability. The thesis of this paper is that conceptualizing human reliability in these terms raises methodological problems that are likely to prevent this goal from being achieved. What is lacking are: a definition of human failure, units of human behavior whose reliability can be determined, a way to synthesize the reliability of larger behavioral sequences from the units if we could specify them, and a way to integrate human reliability, if it could be determined, with equipment reliability. Monte Carlo modeling is seen as a promising approach to the topic.
Subjective Mental Workload
Authors: Moray Neville
Published: July 2017

Subjective workload is of increasing importance in user-machine systems, as the role of the human operator becomes less to control and more to monitor complex systems. This paper reviews the relationship between physical, cognitive, manual-control, and time-stress tasks and the subjective load experienced by an operator. The more important task variables are suggested, as are areas requiring research.
The Bead Game: Response Strategies in Free Assortment
Authors: Bond Alan B.
Published: July 2017

Subjects were presented with a collection of spherical beads of four different colors and were instructed to sort them as fast and as accurately as possible. The sequence in which the beads were sorted was recorded, along with the time intervals between successive beads. Subjects were observed to sort in nonrandom sequences, producing runs in which a given bead type was taken exclusively. The speed and accuracy of the sorting process was positively correlated with the degree of nonrandomness of the sorting sequence. This relationship appeared to be primarily attributable to perceptual factors involved in the initiation of a run and secondarily attributable to facilitation of sorting movements within runs. The effect of sorting sequence was enhanced with bead colors that were harder to discriminate. The results are interpreted in the light of known effects of presentation sequence and stimulus discriminability on stimulus processing.
Estimation of Automobile Speed under Day and Night Conditions
Authors: Triggs Thomas J. , Berenyi John S.
Published: July 2017

Passenger subjects estimated automobile speed while traveling along an unlit freeway under day and night conditions. A visual occluding device allowed a 1-s glimpse of the road ahead when a judgment was required. Although subjects underestimated speeds, their judgments were more accurate at night than during the day.
Using Latex Spheres to Simulate Naturally Turbid Waters
Authors: Williams Jerome , Vaughan W. S.
Published: July 2017

Laboratory research on problems of underwater vision and display optimization for underwater systems has been hampered by the difficulty of representing the light-scattering effects of naturally turbid waters. In the present study, latex spheres of uniform diameter were used to simulate the physical turbidity characteristics of two categories of natural waters: nearshore coastal oceans and inshore harbors and bays. The optical densities of the prepared water samples were measured and compared to samples taken from Chesapeake Bay and Baltimore Harbor. Results recommend the use of latex spheres to represent particle size distributions and concentrations of naturally turbid waters for use as laboratory viewing media in underwater vision and display research.
Determinants Display Legibility in Dark, Turbid Waters
Authors: Vaughan W. S. , Glass Robert A. , Williams Jerome
Published: July 2017

The physical characteristics of naturally turbid near-shore and inshore waters were simulated by substituting latex spheres for natural suspensoids. Four samples of artificially turbid waters were prepared to represent turbidity variations typical of coastal oceanic and harbor/bay waters. These were used as viewing media in laboratory experiments on display legibility. Systematic control of sizes and concentrations of particles suspended in the water enabled the assessment of light-scattering effects as a factor in display optimization for undersea system applications. Scattering phenomena were significant determinants of display legibility in harbor/bay but not coastal ocean viewing media.
Search Time with a Color Display: Analysis of Distribution Funcations
Authors: Carter Robert C.
Published: July 2017

Color displays were used for a search task. The task involved locating a particular three-digit number in a background of other numbers, given the first two digits of the target and its color. The display variables were the number of display items of the same color as the target (TCS); the number of background items not of the target's color (NOB); and the color difference between the target and background items (ΔE). Search times obtained with each of 17 combinations of these conditions were discussed in terms of their cumulative distribution functions (CDFs). The observed CDFs were compared with some theoretical CDFs: normal, linear, and exponential. Search times were normally distributed when targets were immediately obvious to searchers (TCS and NOB small,ΔE large). The exponential CDF was best when the target was less conspicuous (TCS and NOB large, ΔE small) so that searchers had to scan the display to locate the target. The exponential model was improved by addition of a parameter to represent human response time. Furthermore, the parameters of the exponential model were shown to respond in a consistent and theoretically meaningful manner to changes of the display variables.
Perceptual Discriminability as a Basis for Selecting Graphic Symbols
Authors: Geiselman Ralph E. , Landee Betty M. , Christen Francois G.
Published: July 2017

The purpose of this research was to develop a performance-based criterion for selecting among alternative symbols to be used in graphic displays. The specific criterion developed was an index of perceptual discriminability. Through regression analyses of an intersymbol similarity-rating matrix, it was concluded that symbols are judged more or less similar on the basis of the number of shared versus unique configural attributes (an X, a triangle, etc.), as opposed to primitive attributes (number of lines, arcs, etc.). An easy-to-use discriminability-index formula was derived from the regression analysis involving the configural attributes, and this formula was used to predict the results of an experiment involving a search for specific symbols embedded in an array. Indices obtained from a formula such as the one developed here could be used as part of the basis for choosing among alternative candidate symbols for inclusion in an existing symbol domain.
Robotics and Human Factors: Current Status and Future Prospects
Authors: Parsons H. McIlvaine , Kearsley Greg P.
Published: July 2017

Robotics is a new technology domain that human factors scientists and practitioners should enter, to represent the human role in automation. Robots have varying functional capabilities, applications, and rationales. From the perspective of human factors engineering, the most important question is the division of labor between robots and humans. Humans participate in robot systems in nine activities: surveillance, intervention, maintenance, backup, input, output, supervision, inspection, and synergy. Additional concerns include hardware and software design of interfaces with operators, procedure development, accident prevention, and training. There have been a few human factors studies, including some by the Army, Air Force, and Navy (in teleoperators), but more are needed, drawing in part on research in artificial intelligence, to support robotics for industrial productivity and military requirements.
A Survey of Industrial Box Handling
Authors: Drury Colin G. , Law Chau-Hing , Pawenski Christopher S.
Published: July 2017

An analysis was made of videotapes showing more than 2000 different box-handling tasks, performed by workers in nine factories. Sagittally symmetric lifting and lowering tasks were the exception rather than the rule, and there was a high incidence of body twisting as boxes were picked up and put down. Very few boxes had handles; even when handles were provided they were not always used. In the most common hand-hold position, one hand was at the upper-front corner of the box and the other was at the lower-rear corner. This position provided horizontal and vertical stabilization. During those parts of the task in which the subject supported the total weight of the box, this hand position accounted for almost half of the total number of hand positions used. The next most frequently used hand position appeared in fewer than 10% of the tasks. Hand positions were partially determined by subject, box, and task variables. The median box dimensions were 38.0 cm long, 30.5 cm wide, and 21.5 cm high. Median box weight was 9 kg. Most of the reaching occurred when the box was picked up and put down; the box was held relatively close to the body during the rest of the task.
Ergonomic Evaluation of Two-Hand Control Location
Authors: Nemeth Susan E. , Blache Klaus M.
Published: July 2017

Electromyography data were collected on three muscle groups of the arm while subjects performed a task with two-hand control buttons mounted at eye level and at waist level. It was found that EMG energy, an indicator of muscular effort expended, was 4.7 times higher with the eye-level buttons for all three muscle groups.
Effects of Carbon Dioxide Inhalation on Psychomotor and Mental Performance during Exercise and Recovery
Authors: Sheehy James B. , Kamon Eliezer , Kiser David
Published: July 2017

Psychomotor and mental tests involving reaction time, rotor pursuit, short-term memory for digits and letters, and reasoning ability were administered to subjects inhaling up to 5% CO2 in air and in gas mixtures containing 50% O2, The psychomotor and mental tests were given during the 6 min of recovery following 10 min of treadmill running at 80% of aerobic capacity. Although the subjects inhaled the CO2 during the entire exercise and recovery period there was no difference in performance between the CO2 inhalation condition and the control condition for any of the performance measures.
The Effects of Cold on the Performance of Serial Choice Reaction Time and Various Discrete Tasks
Authors: Ellis Hadyn D.
Published: July 2017

Two experiments are reported in which subjects performed a number of tasks before, during, and following exposure to cold. The main performance task, involving serial choice reaction times, yielded consistently large increases in error that were attendant upon reductions in mean skin temperature, and appeared largely independent of any fall in rectal temperature. Other more discrete tasks investigated over the two experiments included a simple reaction time test and the Stroop Word Color Test. The results of these tests indicated no significant performance changes in the cold. Performance on a verbal reasoning test, however, was slightly improved in the cold. The results are discussed in terms of an arousal versus distraction hypothesis of cold effects.
Stimulus Velocity and Movement Distance as Determiners of Movement Velocity and Coincident Timing Accuracy
Authors: Wrisberg Craig A. , Hardy Charles J. , Beitel Patricia A.
Published: July 2017

Thirty right-handed subjects (J 5 males and 15 females) received trials on a timing task that required the completion of a ballistic arm movement coincident with the termination of a moving light pattern. Each subject performed 20 trials under each of nine possible combinations of movement distance and stimulus velocity. The results indicate that timing errors were inversely linked to stimulus velocity and were not related to movement distance. Movement velocity was associated more with variations in movement distance than with changes in stimulus velocity. Males responded with more accuracy and consistency than did females.
The Effect of Repeated Emergency Response Trials on Performance during Extended-Duration Simulated Driving
Authors: Muto William H. , Wierwille Walter W.
Published: July 2017

This investigation studied the effects of 30, 60, and 150 min of continuous driving on drivers' response times to repeated response trials in a simulated emergency--the sudden deceleration of a lead vehicle in a simulated car-following scenario. The results indicated that mean response times of early trials tended to be slower than those of later trials and those of baseline trials. These data imply that repeated response trials can modify decrements normally associated with fatigue mechanisms, and that studies using repeated response trials during driving may not yield valid indications of fatigue-induced performance decrements.
Energy Expenditure and Aerobic Fitness of Male Low Seam Coal Miners
Authors: Bobo M. , Bethea N. J. , Ayoub M. M. , Intaranont K.
Published: July 2017

The physiological responses of male low seam coal miners were measured both above and below ground to ascertain the characteristics and task demands of mining low coal in very restricted surroundings (seam height 1.2 m or lower). Aerobic capacity was estimated from measurements of expired air and heart rate taken while subjects rode a stationary bicycle. Total ventilation (as measured by a respirometer) was used to assess underground energy expenditure and oxygen consumption. Results indicate that low seam coal miners do not have higher maximum oxygen consumption values than non mining populations. Individual task analyses for oxygen uptake and kilocalorie expenditure are discussed.
A Descriptive Model of Visual Search
Authors: Noro Kageyu
Published: July 2017

This study used the corneal reflection technique to investigate causes of miscounting in a dot-counting inspection task. An analysis of subjects' eye movements showed that there were two causes of miscounting: making fewer eye movements than the number of objects to be counted and overlooking objects present in the boundary of the visual field. The type of miscounting depended on the number of dots to be counted and the time allotted. Search process trade-off curves were developed that show the proportion of the two processes in a trial. These curves were incorporated into a descriptive model of visual search.
Multivariate Analysis of the Relationship between Drivometer Variables and Drivers' Accident, Sex, and Exposure Status
Authors: Wilson Tay , Greensmith John
Published: July 2017

Drivers classified by sex, accident history, and driving exposure drove a 50--km route in an instrumented car. Run time, speed changes, fine and coarse steering--wheel reversals, accelerator and brake applications, lateral accelerations, gear changes, traffic--free speed, signals, and overtaking were recorded. Aggression and anxiety tests were also administered, and discriminant analyses were performed on the results. In general, the personality variables did not discriminate between driver groupings. With regard to driving variables, however, significant and important discriminations between groups were made. Accident--involved drivers drove more quickly on clear roads, moved about more, and overtook in traffic. When moderate--exposure drivers were examined, both female and male accident--free drivers were typified by relatively low mean clear speed, infrequent overtaking, and frequently being overtaken. In addition, accident--free females used the brakes relatively infrequently. Accident--free males did not move the car about in traffic. Overall, high--exposure male drivers tended to drive relatively quickly, but those who were accident free were typified by adjusting their car to changing conditions (brake applications, gear changes, accelerator applications, and possibly coarse steering--wheel reversals).
RESEARCH NOTE Eyestrain in VDU Users: Physical Correlates and Long-Term Effects
Authors: De Groot Jan P. , Kamphuis Andre
Published: July 2017

Subjects in the Dutch telephone inquiries services were studied just before, just after, and two years after the introduction of VDUs. Number, type, and severity of complaints did not change over time. Optometric measures were not useful for predicting complaints and showed no deterioration other than aging effects.
Continuous Noise and Sensorineural Hearing Loss: A Case Study
Authors: Ellis Newton C.
Published: July 2017

Twenty-nine audiometric tests undergone by an employee over a 26-year employment period in a structural maintenance shop at a large petrochemical company are analyzed. At retirement, the employee was diagnosed as having irreversible sensorineural hearing loss. Since company studies yielded average noise level measurements of 90 dBA within 1.83 m of operating equipment, the relationship between continuous noise and sensorineural hearing loss in the conversational frequencies is examined. Results suggest that the relationship is linear, and that auditory capability consistently deteriorates over long periods of exposure.
A Study of Size, Distance, Height, and Frequency Effects on Manual Handling Tasks
Authors: Ciriello Vincent M. , Snook Stover H.
Published: July 2017

The effects of size, distance, height, and frequency on lifting, lowering, carrying, pushing, and pulling tasks were studied in two series of experiments using a psychophysical methodology. In the first series, 10 male and 12 female industrial workers performed tasks at many different frequencies. Results indicate that the lower-frequency tasks (especially the 5-min and 30-min tasks) have acceptable weights and forces lower than those estimated in previous studies. In the second series, 12 female industrial workers performed tasks with a variety of box sizes, distances of lift, and heights of push and pull. Results indicate that maximum acceptable weights and forces for female workers are significantly lower, but proportionally similar, to the maximum acceptable weights and forces for male workers.
Volitional Postures during Maximal Push/Pull Exertions in the Sagittal Plane
Authors: Chaffin Don B. , Andres Robert O. , Garg Arun
Published: July 2017

A set of push/pull experiments was performed by six men and women of varying anthropometry who were asked to exert maximal one-handed and two-handed push and pull forces on a load cell set at three different heights (67, 109, and 152 cm). They were each permitted to experiment with their postures to determine that which they sensed would permit the largest push or pull force, though no direct feedback was given as to their actual performance. Once they achieved what they believed to be their optimal posture, sagittal-plane photographs were taken. The angles of major body joints were then recorded along with the isometric force produced.

It is shown that foot placement, handle height, and body postures affect push and pull force capability in a manner that is reasonably logical, using biomechanical concepts. It is proposed that future biomechanical models of push an pull strengths and workplace layouts must be carefully assessed with reference to the postural variations reported.
The Effect of Display Format on the Direct Entry of Numerical Information by Pointing
Authors: Long John , Whitefield Andy , Dennett John
Published: July 2017

Pointing is in many cases now a viable alternative to keying for the on--line entry of numerical data. This study compares three formats for the arrangement of the numerical display for use by inexperienced operators. The three formats are a linear array, a matrix array, and a cash register array. The particular layouts of each of these formats were optimized using the results of a preference study and an experimental pretest. The results of the main experimental comparison suggest that the linear and the matrix formats are about equally suitable for this task, and both are more suitable than the cash register format, although there are circumstances in which the cash register format performs equally well. Factors influencing performance, and thus those that should be considered in the choice of format for any particular application, are discussed.
Perceived Threat and Avoidance Maneuvers in Response to Cockpit Traffic Displays
Authors: Smith J. D. , Ellis Stephen R. , Lee Edward C.
Published: July 2017

Airline pilots rated their perception of the danger of an air-to-air collision based on cockpit displays of traffic information while they monitored simulated departures. They selected avoidance maneuvers when necessary for separation. Most evasive maneuvers were turns rather than vertical maneuvers. Evasive maneuvers chosen for encounters with low- or moderate-collision danger were generally toward the intruding aircraft. This tendency lessened as the perceived threat level increased. In the highest threat situations, pilots turned toward the intruder only at chance levels. Intruders coming from positions in front of the pilot's ship were more frequently avoided by turns toward than when intruders approached laterally or from behind. Some of the implications of the pilots' turning-toward tendencies are discussed with respect to automatic collision avoidance systems and coordination of avoidance maneuvers of conflicting aircraft.
Operational Efficiency and Time of Day
Authors: Craig Angus , Condon Ruth
Published: July 2017

Forty-eight subjects performed a battery of six predominantly perceptual tasks that were relevant to bridge operations on a ship at sea. Sessions were run at six times over an extended waking day, between 0800 and midnight. For some of the tasks performance was noticeably deficient at certain times of day, the diurnal pattern corresponding approximately with that in activation and alertness. However, closer examination of the data reveals that although a genuine efficiency deficit may exist at particular times, a major part of the variation in performance can reasonably be attributed to a shift in the trade-off between speed and accuracy. Because the direction of the shift is towards faster but less careful performance as the day progresses, the shift may be due to accumulating fatigue rather than to time of day per se. Regardless of the primary cause, vulnerability may be increased at certain times due to a slump in operational efficiency.
Visual Search Processes in Camouflage Detection
Authors: King M. G. , Stanley G. V. , Burrows G. D.
Published: July 2017

Recent models of visual information processing have been applied to the results of a search/ detection task involving photographic slides of concealed soldiers. It was postulated that since camouflaged persons could be regarded as examples of threshold items, automatic detection should not occur. Even for relatively low-load (easy) items, reaction times were slower than those that would have been expected had automatic detection occurred. The systematic increase in reaction time with task load implies that feature-integration processing was required to achieve target detection. In pointing towards a possible strategy for target detection using real-world stimuli, the results of this report may be important in the design and interpretation of camouflage detection trials.
Pilot Differences and Motion Cuing Effects on Simulated Helicopter Hover
Authors: Ricard Gilbert L. , Parrish Russell V.
Published: July 2017

The effects that cues of aircraft motion, delays in visual scene, and movement of a ship model have on pilots' ability to hover a simulated helicopter near a destroyer-class ship were examined. Twelve pilots were tested in a within-subject factorial combination of fixed-base, moving-base, and G-seat conditions in which delays of 66 or 128 ms existed in the simulator's visual display and the pilots had to hover near a moving or stationary ship. Best control performance was seen under the moving-base conditions, whereas poorest control was associated with the fixed-base simulation. An intermediate level of performance was produced by the G-seat. In addition, visual delay affected control of the roll axis of the simulation, and interactions between pilots and motion cuing and visual delay were seen. little effect.
What Makes a Difference When? Comments on Grudin and Barnard
Authors: Landauer Thomas K. , Galotti Kathleen M.
Published: July 2017

Taken together with earlier work on command naming, Grudin and Barnard's results suggest that “specificity” and “meaningfulness” may be important while “naturalness” is not. However, important methodological problems are raised by experiments like this, in which conditions are arranged to maximize the effect of theoretically interesting variables while reducing overall similarity to real tasks.
A Multidimensional Scaling of Video Games
Authors: Bobko Philip , Bobko Douglas J. , Davis Mark A.
Published: July 2017

Ten video games currently used in commercial markets were subjected to pairwise similarity ratings. A multidimensional scaling of the responses revealed three underlying dimensions that accounted for 30% of the variance: destructiveness, dimensionality, and graphic quality. These three dimensions are readily interpretable, can be embedded within personality and motivation literatures, and have application to the design of computer-based training devices.
The Relationship between Personality and Irrational Judgment in Civil Pilots
Authors: Lester Lewis F. , Bombaci Deborah H.
Published: July 2017

The construct validity of five “hazardous thought patterns” that are hypothesized to mediate pilot judgment was examined in a sample of 35 civil pilots using a self-assessment inventory developed in previous FAA research. A significant relationship was observed between three of the hazardous thought patterns and scores on both the 16PF integration/self-concept control scale and the Rotter locus of control scale. No relationship to 16PF impulsivity or superego strength was noted. The implications for pilot training and certification are discussed.
Television Viewing at Home: Distances and Visual Angles of Children and Adults
Authors: Nathan John G. , Anderson Daniel R. , Field Diane E. , Collins Patricia
Published: July 2017

Television viewing distances, visual angles, and viewing angles were calculated for 217 children and 149 adults from 78 families. The data were obtained from time-lapse videotapes automatically recorded in the families' homes over 10-day periods. Viewing distance increases with age, and visual angle decreases with age. Viewers aged 17 years and younger viewed at an average distance of 225.3 em, at an average visual angle of 12.3 deg, and at an average viewing angle of 23.7 deg. Adult viewers watched TV at an average distance of 336.8 cm, an average visual angle of 6.6 deg, and at an average viewing angle of 23.3 deg. The best predictors of viewing location were (1) percentage of time the viewer watched TV from furniture, (2) room area, and (3) screen width.
Human Behavior Feedback and Traffic Safety
Authors: Evans Leonard
Published: July 2017

A general human behavior feedback formalism is developed in which the actual safety change in traffic systems is related to the intended or expected change through the introduction of a "human behavior feedback parameter," f. This formalism includes earlier approaches to modeling or understanding traffic safety as special cases and in addition includes responses outside the range encompassed by the earlier approaches. It is applied in an essentially symmetric way to changes expected to increase or to reduce safety. Compared with the expected safety change, the actual safety changes found in 26 studies in the literature provide examples of all of the following: change even greater than expected; as expected; smaller than expected; no safety change; and a perverse effect (safety change opposite in sign to expected). It is concluded that human behavior feedback is a pervasive phenomenon in traffic systems, and one that may greatly influence the outcome of safety measures.
A Reliability Study of Task Walk-Through in the Computer/Communications Industry
Authors: Francas Mark , Goodman David , Dickinson John
Published: July 2017

One characteristic of the computer and communication industry is the speed with which innovation and change occur. This volatility poses special problems for the researcher involved in human factors issues in this field. A case study is reported in this paper that describes the application of cost-effective simulated trials in product design and product enhancement. A subsequent study, using more conventional research methods, is described that assessed the replicability of simulations. The results from these studies lead to the conclusion that simulated user trials are both a useful source of preliminary data to guide further evaluation and may also constitute an effective and economically viable method of providing direct input to the product development process. The procedures described offer options to human factors specialists in the computer and telecommunications industries.
Performance of Disabled Persons on a Chordic Keyboard
Authors: Kirschenbaum Alan , Friedman Zwi , Melnik Arie
Published: July 2017

Fourteen disabled persons used a one-hand chordic device for typing. This keyboard was designed to minimize physical exertion and to inhibit unwanted psychomotor reactions so as to facilitate its use by persons with cerebral palsy, muscular dystrophy, and related disorders. The keyboard fits the fingers of one hand. A character is typed by pressing a combination of fingers corresponding to a typing code developed earlier. Typing rates of text transcription ranged from 8 to 14 words/min after 5 h of practice. These results indicated that the physical configuration and cognitive operation of a chordic keyboard would permit disabled persons to use computers.
Effects of User Insertion/Donning Instructions on Noise Attenuation of Aural Insert Hearing Protectors
Authors: Casali John G. , Epps Brian W.
Published: July 2017

An experiment was performed to examine the influence of different levels of insertion instructions on the noise attenuation achieved with five common universal-fit protective earplugs. Five insertion conditions were investigated; these required earplug placement by subjects with no instruction, with auditory feedback, with manufacturers' on-package instructions, with detailed written and pictorial instructions, and with experimenter-modeled earplug insertion procedures. Attenuation data were obtained using REAT (real-ear attenuation at threshold) test procedures on 50 subjects. The results indicated that insertion-instruction strategies posed a major influence on the level of attenuation to be realized with the earplugs, and that earplugs were differential in their sensitivity to instruction. In some instances, attenuation afforded by no instruction was tripled when more comprehensive instructions were presented to the subjects.
An Experimental Evaluation of Method and Tool Effects in Spike Maul Use
Authors: Marras William S. , Rockwell Thomas H.
Published: July 2017

An experiment was performed to study the effects of hand-tool design factors and methods of tool use upon tool force generation and loading of the back. Forty novice and experienced subjects were tested on their ability to drive a spike with a railroad spike maul. Method of tool use affected the spike-driving performance of novice subjects, whereas tool striking surface area influenced the ability of experienced trackmen to drive spikes. Method of tool use also affected the components of spine loading. Tool force generation was considered as a function of spine loading indices to create efficiency measures. Efficiency was used to evaluate the cumulative trauma effects of the hand tool.
Results of the Simulation of a Qualitative Information Display
Authors: Mital Anil , Ramanan Sukumar
Published: July 2017

Check-reading tasks were simulated to determine the effects of several task- and worker-related factors on human performance. The purpose of this study was to investigate the influence of: operator sex, exposure time, pointer position, percentage of deviant dials, and background color on the accuracy of check-reading dials. Twenty-eight males and 22 females performed the simulated tasks. No difference was found between the 9 o'clock and the 12 o'clock positions. For shorter exposure times (0.25 and 0.50 s), dials with white background were found superior. However, with 0.75 s exposure time the black dial background was found superior. Even though males did better than females overall, there were no differences between the sexes when exposure time was increased to 0.75 s. Performance was found to be independent of the percentage of deviant dials between 1% and 3%.
Fatigue and Reading of Text on Videotex
Authors: Nordqvist Tommy , Ohlsson Kjell , Nilsson Lars-Göuran
Published: July 2017

Three experiments are reported in which the effects of fatigue are studied during the reading of texts presented by means of a videotex system or by means of print on paper. For both these presentations the viewers read texts for a period of 2 h. The reading task was interrupted six times for tests of speed and accuracy in scanning a matrix of letters for given target letters, speed and accuracy in an auditory-motor reaction time task, and a free recall test of the information presented immediately prior to each test session. The three experiments differed with respect to task demands. Experiment I was less demanding than Experiment 2, which in its turn was less demanding than Experiment 3. It was predicted that those viewers who read the texts presented on videotex would show more dramatic effects than the viewers who read texts under more regular print-on-paper conditions. It was also predicted that these effects would be more pronounced for more demanding tasks. The results, however, demonstrated only marginal effects of fatigue. The effects of fatigue were somewhat more pronounced in the videotex group.
The Optimal Number of Menu Options per Panel
Authors: Paap Kenneth R. , Roske-Hofstrand Renate J.
Published: July 2017

As the number of levels of a hierarchical menu structure grows, users find it difficult to navigate from their current location to their desired location. Despite the navigation problem, designers of menu interfaces may want to trade more depth for less breadth in order to take advantage of funneling. Indeed, Lee and MacGregor (1985) have presented an analysis of search time that suggests that the optimal number of options per menu panel over a wide range of conditions is in the range of only four to eight. However, Lee and MacGregor's analysis applies only to cases where the user cannot restrict the scope of search based on either experience with the menu panel or on the organization of the options on the panel. The analysis is extended to cases of restricted search. Assuming optimal grouping, the optimal number of alternatives on a single page ranges from 16 to 78 across the same parameter values explored by Lee and MacGregor.
Optimizing the Structure of Database Menu Indexes: A Decision Model of Menu Search
Authors: Macgregor James , Lee Eric , Lam Newman
Published: July 2017

The paper investigates the issue of the optimal number of alternatives that should be placed on database menu pages. A previous search-time model (Lee and MacGregor, 1985) is extended by proposing a criterion-based decision model, which makes predictions about how the number of alternatives affects the search process and the pattern of errors that will result. An experimental test of the model largely supported the predictions and indicated that with naive users the optimal number of alternatives per page is four to five. These values resulted in the shortest search times, the highest success rates, and the highest preference rankings.
Drowsy Driver Detection Using Discriminant Analysis
Authors: Skipper Julie H. , Wierwille Walter W.
Published: July 2017

Driver drowsiness represents a serious hazard, and methods need to be developed to detect and counteract its effects. In this research, 14 dependent driving variables were investigated for their potential use in predicting driver drowsiness and, in particular to this research, eyelid closure. A computer-controlled automobile simulator was used to simulate a nighttime highway driving scenario for 20 drivers in both a rested and a partially sleep-deprived condition. Included in the simulation approximately every minute was one of two types of driving stimuli, torque or displacement. The responses of the drivers to these stimuli and the general driving characteristics of the drivers between stimuli were recorded. These data were subsequently analyzed using linear discriminant analyses. The discriminant analyses indicated that a number of dependent variables contributed to linear discriminant functions, which classified “alert” and “drowsy” observations with relatively low false-alarm and miss rates.
The Effects of Age, Sleep Deprivation, and Altitude on Complex Performance
Authors: Mertens Henry W. , Collins William E.
Published: July 2017

This research examined the potential interactions of age, sleep deprivation, and simulated altitude (gas mixtures). Healthy men aged from 30 to 39 years (N = 16) and from 60 to 69 years (N = 14) participated in the four possible combinations of two altitudes (ground versus 3810 m) and two sleep conditions (sleep permitted/sleep deprived). Sleep deprivation involved loss of one night's sleep. Following training, complex (time-shared) performance was tested during three-hour sessions in the morning and afternoon of each of four test days. Tasks included monitoring of warning lights and meters, mental arithmetic, problem solving, target identification, and tracking. Workload was varied within each hour by varying the tasks performed simultaneously. There was a significant interaction of sleep deprivation and altitude that was enhanced by increasing workload. When the subjects were sleep deprived, performance was significantly lower in general, and the greatest decrement in performance occurred at altitude. The performance of older subjects tended to be lower and more affected by increases in workload than was that of younger subjects, but the detrimental effects of sleep deprivation or the combination of sleep deprivation and altitude did not appear to interact with age.
Advantages and Disadvantages of Rapidly Rotating Shift Schedules—A Circadian Viewpoint
Authors: Monk Timothy H.
Published: July 2017

This report uses some previously published data to explore the benefits and drawbacks associated with rapid shift rotations of less than five days, comparing them with slowly rotating and with fixed shift systems. The discussion is limited to circadian (“biological clock”) issues, and concludes that one must look at the whole situation (including job type) before coming to a decision, and that no option should be ruled out on a priori grounds.
Processing Demands, Training, and the Vigilance Decrement
Authors: Williams Peter S.
Published: July 2017

Two possible sources of vigilance decrement are inadequate training of operators and taxing information-processing demands. This study attempted to compensate for both of these sources. Although compensation for training was effective, processing demands may have been set too high, as detection sensitivity declined. This result suggests that an event rate much less than the current threshold of 24/min is necessary to stabilize sensitivity. Response latency increased progressively during the task and was greater for “unsure” as compared with “sure” decisions. Consistent with an adaptation-level hypothesis, reduced sensitivity was compensated by a general negative shift in response bias. This adaptive process may account for the absence in this study of the usual form of vigilance decrement: a positive shift in bias, which reduces both detection and false-alarm scores.
The Influence of Visual Workload History on Visual Performance
Authors: Matthews Michael L.
Published: July 2017

Two experiments are reported that demonstrate that visual search for a signal from a number of potential signal sources in a sustained monitoring task is dependent upon previous visual-load history. It is shown that both temporal and spatial variations in load produce performance decrements, and occasionally increments, that cannot be predicted from static-load experiments. These data are not consistent with previous attempts to explain performance changes associated with workload history. An interpretation is offered in terms of the persistence of information-processing strategies across changing task conditions.
Evaluation of Short-Range Roadway Delineation
Authors: Good Malcolm C. , Baxter Graham L.
Published: July 2017

A distinction is drawn between long- and short-range delineation, the latter being provided to aid the driver in tracking the roadway at night and under poor visibility conditions. A quasi-linear describing function approach is employed to represent the driver as a sensor and controller, and it is hypothesized that reductions in the quality of the driver's visual field will be reflected by an increase in the level of the “remnant” (interpreted in part as visual observation noise). Experiments were performed on a rural road, to which a variety of delineation treatments were applied, using a vehicle that permitted the identification of driver-vehicle describing functions as subjects negotiated the test course. The results are generally supportive of the experimental hypothesis, with the describing function parameters yielding evaluations of delineation treatments that are consistent with each other and with subjective ratings of task difficulty.
Psychophysical Modeling of Manual Materials-Handling Capacities Using Isoinertial Strength Variables
Authors: Jlang Bernard C. , Smith James L. , Ayoub M. M.
Published: July 2017

Strength testing has been used to determine a worker's physical capacity as well as to screen an individual for placement in future employment. A comparison is made of the relationships between two types of strenght tests (isometric and isoinertial) and the manual materials-handling (MMH) capacities of individuals. Four MMH activities were evaluated: lifting from floor to knuckle height, lifting from knuckle to shoulder height, lowering from knuckle to floor height, and carrying for a 4.3-m distance. Psychophysical capacities were determined under three frequency conditions: one-time maximum, 1 lift/min, and 6 lifts/min. I soinertial 1.83-m maximum strength (Tl), tested on the incremental weight-lifting machine, proved to be the most highly correlated strength test to the capacities for MMH activities. Second-order polynomial regression models for MMH capacities were developed using T1as a predictor. The isoinertial strength test T1 is recommended as the most promising single screening test because of its simplicity and task similarity.
Sensitivity of Human Tactile Inspection
Authors: Kleiner Brian M. , Drury Colin G. , Christopher Gregory L.
Published: July 2017

Human performance in an inspection task involving the active probing of cracks in metal cylinders with a hand-held probe was measured. Detection probabilities of novice and experienced inspectors were measured for each of a range of crack widths. For both subject groups, detection probability increased with increasing crack width and with decreasing probe-tip diameter. Novice inspectors given one hour of training had detection probabilities comparable to those of experienced inspectors.
Radiation Search and Detection by Ear and by Eye
Authors: Tzelgov Joseph , Srebro Rafi , Henik Avishai , Kushelevsky Abraham
Published: July 2017

Most radiation monitors in use employ visual displays. In some cases the monitor has an auditory display, but even then the operators are usually instructed to rely mainly on the visual information. It is not clear, however, that the visual mode is to be preferred. The present project focuses upon the relative efficiency of various types of information that can be provided by radiation monitors. Two experiments were conducted. In the first, the subjects were asked to perform a search task. The second evaluated performance in a detection task. The main independent variable of interest in both experiments was information mode; that is, the mode of providing information about the radiation level. We compared three modes of providing the information: auditory, visual, and redundant (both auditory and visual). It was found that in the detection task the three modes of information resulted in identical levels of performance. In the search task, however, the auditory display resulted in a better performance than did either the visual display or the redundant condition. The results are consistent with the concepts of visual dominance and visual bias as suggested by Posner et al. (1976). The implications of the findings are discussed.
Reading Is Slower from CRT Displays than from Paper: Attempts to Isolate a Single-Variable Explanation
Authors: Gould John D. , Alfaro Lizette , Barnes Vincent , Finn Rich , Grischkowsky Nancy , Minuto Angela
Published: July 2017

People read more slowly from CRT displays than from paper (see, for example, Gould and Grischkowsky, 1984). This report summarizes ten experiments and several more analyses that seek to explain the cause of this reading-speed difference. Typically, each experiment isolates one variable and studies whether it explains the difference. Results show that no one variable studied (e.g., experience in using CRT displays; display orientation; character size, font, or polarity) explains it. The tentative conclusion is that the difference is due to a combination of variables, probably centering on the image quality of the characters themselves.