Proceedings of the Human Factors and Ergonomics Society Annual Meeting

Methods are discussed for studying functional brain based disorders hypothesized to be the result of systems dysfunction rather than specific structural deficit.

Detection of human visually evoked electrical responses (VER) requires direct electrode contact which results in greater recording variability and artifact. A new alternative method exists, termed the visually evoked magnetic response (MVER), which is free from such complications and interference. A brief review of the development of the technique is presented and a proposal to adapt the method into a potentially useful diagnostic tool is discussed.

The paper is concerned with design considerations for the development of visual prosthetics which by-pass the site of dysfunction in the visual system. Pattern recognition and cognition as well as image synthesis and processing considerations are addressed.

This paper describes an investigation which assessed the feasibility of the event related brain potential (ERP) to provide an index of operator workload in adaptive man-machine systems. The characteristics and requirements of such systems are described and some limitations of secondary task workload measures enumerated. The results of an experiment are then presented in which ERPs were recorded from 10 subjects, while the difficulty of a concurrent tracking task was varied. Subjects performed either a one or a two dimensional compensatory tracking task, while ERP's were elicited by presenting discrete auditory stimuli. The amplitude of the P300 complex, a component of the ERP, elicited by the stimuli, decreased from the control condition (no tracking) to the tracking conditions. An ERP based measure of sequential processing of the stimuli was further affected as tracking difficulty was increased from 1 to 2 dimensions. An algorithm for obtaining an on-line ERP based measure of workload is then described.

The Federal Trade Commission (FTC) has the responsibility for determining what may be reasonably expected of consumers in their fulfillment of the terms of a consumer product warranty. The problem of defining consumer product portability within the context of a consumer product return activity is discussed and the results of a controlled experiment which directly relates to the task of establishing maximum reasonable product weight for a consumer product return activity are presented. Distributions of maximum reasonable weight for product return are presented and recommendations are given for warranty rulemaking. Continuing research aimed at developing a consumer product portability index is summarized.

A study was conducted to determine the type of signs that consumers would select as the most efficient warning label to be placed on a power mower. The Consumer Product Safety Commision is considering the implementation of a safety regulation for mowers that would consist of some combination of warning signs, deadman switch and/or clutch to reduce an estimated 112,000 injuries annually. Eighty-four percent of those interviewed responded that the addition of a warning sign could reduce injuries. Safety sign variables, and the implications of survey data for human factors design are some of the points discussed in this paper.

The Poison Prevention Packaging Act of 1970 was the culmination of an effort lasting over a decade. The purpose of this act was “to protect children from serious personal injury or serious illness…” as the result of gaining access to hazardous household substances. The purpose of the investigation reported in this paper was to analyze three commonly available safety caps (plug-key), arrow line-up, and push-turn types), comparing them with one another and with standard types (snap and twist off) for a large group of children (99) aged 2, 3, 4, and 5 years, male and female. Testing procedures resembling those required under the federal standard were employed with two important exceptions: (1) children were not shown how to gain entry to the containers and (2) the period of attempted entry was reduced to two minutes. Incentives were placed in the containers to stimulate interest. Analysis of successful and unsuccessful entries was conducted with respect to container type, age, and sex. Several significant effects were noted. The push-turn type of safety cap proved most effective, followed by the arrow line-up and slot-key types. The percentage of successful entries was directly related to age. The statistics also revealed evidence questioning the effectiveness of some caps in meeting the federal standard. A detailed motion analysis was conducted on all subjects to study their investigative behaviors in attempting to gain entry to the containers. In testing subjects, all data were recorded on reel-to-reel video tape, permitting instant replay and micromotion analysis using slow motion and stop action viewing. A taxonomy and a frequency chart for these motions were then constructed.

Designing a hand-held control unit for a single-sideband citizens-band (CB) radio involved combining several research techniques and involved specialists from the areas of human factors, marketing, industrial design, and engineering. Task analysis and operational sequence studies were conducted, and expert and informed opinions were gathered from many people during the initial stage of the research. These were followed by a driving simulation to compare a hand-held control unit with a more conventional CB radio in terms of safety and to answer some basic questions about case and keyboard configurations. Four surveys were conducted during various stages of the control unit's development to collect consumer opinions on all aspects of the product. The entire research effort of approximately 4 months involved only one or two human factors specialists to provide the needed information in a timely manner.

Previously reported application of Systems Analysis of Integrated Networks of Tasks (SAINT) to the Digital Avionics Information System (DAIS) was refined against extensive empirical data produced in man-in-the-loop experiments. The current work demonstrates the process of abstracting task characteristics from human performance data. Emphasis is shown to be required in the areas of the organization of the data, task representation, and threshold levels. Four specific experimental conditions, representative of a dual-task study, are reported along with the corresponding SAINT simulation performance predictions.

An operational model was developed for a series of five tasks and four job performance aids. The tasks were defined by both speed and accuracy constraints. Each aid was described in terms of its efficacy on task performance, i.e., time and errors. The developed model was transcribed into SAINT in order to simulate and to compare different combinations of each task's speed and accuracy constraints under various levels of speed stress. Mean task time was found to be a function of task constraints and the JPAs matched to those constraints. Performance time was found to decrease when JPAs were reassigned if initial JPA assignments failed an evaluation criterion test. Performance time continued to decrease when a state of organizing stress was induced by reducing the overall available task time to perform the task series. The continued reduction of the overall available time reached a point at which the stress became disorganizing and caused mean task time to increase.

A review of the research literature on the design of controls and displays is presented with respect to its application to the design of industrial control rooms such as in railroad yards, chemical plants, refineries and power plants. Differences between designing for military and aircraft systems and industrial systems is discussed. The principle display and operator variables that require further research are: (1) measures of the difficulty of using a display system, (2) measuring the attention capacity of the operator, (3) the effect of the level of abstraction of the information, (4) measurement of the operator's image of the system being controlled, (5) the effect of job experience and training on the approach of the operator of the system and (6) the effect of the age of the operator.

This paper summarizes an investigation of the effects on human task performance of color coding in visual displays relative to coding by achromatic letters, digits, and familiar geometric shapes. The results of the investigation provide a comprehensive assessment of the potential advantages and disadvantages of color coding. It is concluded that color coding offers no special property for coding visual displays.

Two experiments studied the relation of illumination level and practical task performance, and the effects of age. Performance improved with illumination and declined with age. The North American illumination standards seem adequate but not excessive.

In two laboratory experiments, involving 282 observers and using aerial photographs, 155 camouflage conditions were evaluated. When compared with sixteen scenes containing un-camouflaged targets, 46 of these conditions produced significant increases in search time. On the basis of this research, several ways of delaying, or preventing altogether, the detection of ground tax-gets from the air are suggested.

Responses to electrocutaneous stimulation were investigated using the two point discrimination threshold as a means of providing information about the range of sensitivity to electrical stimuli.

A complete factorial design was used to investigate the effects of frequency, pulse width, and phase shift on the threshold distance at which two electrocutaneous stimuli can be discriminated. Results were analyzed by an analysis of variance.

The two point discrimination threshold was found to be significant for frequency, pulse width, and the interaction between pulse width and phase shift. Electrocutaneous sensitivity was determined by the level at which the minimum two point discrimination threshold occurred.

Applications of Central-Composite Designs (CCD) in human factors research are reviewed briefly. A recent application of the CCD to the manipulation of task variables is discussed. The use of this approach in the evaluation of a computer-generated aircraft area navigation control-display system is outlined, showing how this approach can be used to evaluate system/operator performance systematically and economically across a wide range of task and environmental variables.

Repeated measures designs have been suggested as being inappropriate in most ergonomic research because of the presence of unwanted order effects which bias the results. Poulton has discussed a number of studies in several areas in which such order effects have rendered the interpretation of the results unreliable. The present study investigated order effects by combining in a single experiment a between-subjects design and a within-subjects design. Eight subjects were exposed to four combinations of two stressors, noise and ice-pressor, in a character recognition task based on reaction time measures. The experimental layout included order as an independent variable and found a significant main effect for treatments (F = 10.89, p < .005). More importantly treatments were found to interact with order (F = 3.26, p < .05). Because of the economy of repeated measures designs in terms of subject number, it is suggested that rather than categorically abandoning their use, research should be undertaken to determine: (1) if order effects are always present; (2) with what variables and combinations of variables they occur; (3) the consistency of such effects in terms of magnitude and direction; and (4) the practical as well as the statistical significance of particular order effects. In addition, the issues of individual differences and intra-subject consistency are discussed in relation to repeated measures designs. Finally, it is suggested that the discrimination of those situations where repeated measures designs can be used effectively is a more practical and fruitful activity than the wholesale elimination of repeated measures from erogomics research.

The working posture of an individual influences his working efficiency and working efficiency significantly affects productivity. An index of productivity as a function of posture-related variables is needed to assess the significance of posture's effect on productivity. A posture-productivity index expresses the capability to increase productivity by changing working posture. The index is based upon the following nine ergonomie guidelines or contributing factors for working posture described by Ayoub (1971): static work, overload of muscular system, mechanical advantage, joint positions, unnatural postures, proper sitting posture, allowable change of posture, accommodation of large operators, and operator training. The advantage of this procedure is not only to be able to determine the posture-productivity index, but more importantly, the capability to improve worker efficiency by modifying working posture is indicated. Such an indication will be an invaluable tool, especially since most changes to improve working posture would normally require minimal investment.

This paper reports a study that was conducted to select 3 or 4 tone signals from a set of 16 related signals with the criterion that the chosen signals sound as much alike as possible. The signals were required to be different for machine recognition purposes, but should sound alike to people to avoid possible confusion. The study employed a multidimensional scaling technique called INDSCAL to assess the similarity relationships among the 16 candidate signals. Twenty-two subjects provided similarity estimates on a 7-point scale for all possible pairs of signals. A 3-dimensional INDSCAL solution was found to describe the data adequately, and the required signals were chosen on the basis of their clustering in this space. The study demonstrates the use of multidimensional scaling to solve practical problems.

A criterion-referenced test keyed to an individualized, self-paced instruction program was developed as part of a diagnostic testing/shipboard training system. The job-based test described hypothetical situations that were based on known job requirements. Under each such situation, questions were asked that required the demonstration of skills and knowledges that supported the job and were covered in the various modules of the instruction program. High face and content validity were ensured by using cards, charts, diagrams, and illustrations in presenting each job situation; and by having job experts write test items. Items were selected that best discriminated between graduates and nongraduates of a shorebased program using the same instruction. The cutoff score for the set of items pertaining to each module was determined from the performance of graduates of the shorebased program and applied to a cross-validation sample. Test scores from two administrations were used to estimate the reliability of the diagnostic decision making.