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Recent evidence suggests that a useful metric of color contrast can be formulated in terms of distance between colors in a perceptually uniform color space. The present research adds to this evidence by presenting equations which relate distance in several spaces to response speeds for reading colored numerals superimposed upon colored backgrounds. The results suggest that several extant uniform color spaces provide no definite advantages over the (nonuniform) 1931 CIE tristimulus space and that improvements can be obtained by rescaling their axes. Two computationally simple metrics are presented which model global color contrast and color contrast complexity.

This study investigated the effects of several alphanumeric keyboard characteristics including: audible feedback; location, size, and shape of the carriage return key; and the shape and style of keycaps. Four of the six keyboards were experimental prototypes, while the remaining two were production models.Eighteen subjects were used in a mixed factorial design. Subjects performed a text entry task during which they were not allowed to correct any errors. Four types of data were collected: 1) total errors per trial, 2) total time for text entry, 3) individual preference questionnaire data for each keyboard, and 4) comparative questionnaire data across keyboards. Results indicate that time on task was not significantly different among keyboards; however, with audible feedback, a marginally significant result was found. Highly trained typists committed significantly more errors than did the other two less experienced groups. Subjects indicated that the location, size, and shape of the return key were important factors for keyboard design. Across groups, subjects preferred the capability for audible feedback.

The effects of manipulating image noise and image blur were determined on an information extraction task using soft-copy displays. The participants in this study were 15 military photointerpreters from Langley Air Force Base, Virginia. The empirical findings indicated that the main effect of image noise was statistically significant (p < 0.002) as was the main effect of image blur (p = 0.060). The noise by blur interaction was not statistically significant (p = .872). In general, image interpretation performance decreased with increasing image noise and image blur levels. This pattern of results was very similar to the empirical observations of a previous study which employed the same image and task conditions for hard-copy displays.

This study investigated how rotation of dot-matrix characters influenced human performance, measured by the response time in a random search task. Factors that influence the extent of dot-matrix pattern distortion were identified, and their effects were investigated. Significant effects were found in angle of rotation (p=0.0046; 0 to 180 degrees in a 5-degree increment), target character's distance from the center of rotation (p<0.0001), and target characters (p<0.0001). Issues pertinent in predicting the effect of dot-matrix pattern distortion on performance are discussed.

Rapid technological transition from analog images to digital images has necessitated the development of a research program for evaluating digital image quality. This paper investigated the perceived interpretability of static, digitized monochrome images displayed on CRTs. Quality judgments of two image degradations: blur and noise, were evaluated by a subjective scaling technique.The digital images consisted of 10 scenes, each of which was degraded by 5 levels of blur and 5 levels of noise, yielding a set of 250 images. Fifteen Air Force photointerpreters participated in the study. The photointerpreters viewed the images on CRTs and rated the interpretability of each image on a 10-point NATO scale.Analysis of the scaling values indicated that the blur, noise, and interaction effects were statistically significant. Perceived interpretability of the images decreased monotonically as the physical image degradation increased.In a separate study, the photointerpreters extracted information from a selected subset of images. Correlation between the scaling values and the actual information extracted was high. This result suggests that information extraction performance can be accurately predicted from subjective quality judgments.Comparisons between CRT-displayed imagery with film-based digital imagery showed no differences. Subjective quality judgments were similar for the two display formats.

This paper presents the perspective of a user system knowledge continuum which recasts traditional user system components (user interface, context-sensitive help, completion aids, manuals, training) as interrelated knowledge components tasked with appropriately distributing required knowledge between user and system. It suggests that maximizing user system effectiveness is best viewed as optimization of a set of such knowledge components. The paper relies upon a case study showing this perspective at work in the development of APT - Applications Productivity Tool™, an integrated software environment for industrial automation applications.

A comprehensive long range human factors plan for nuclear reactor regulation was developed for the U.S. Nuclear Regulatory Commission by a Study Team of the Human Factors Society. This Study Team was selected by the Society to provide a balanced, experienced human factors perspective to the application of human factors scientific and engineering knowledge to nuclear power generation.The Study Team identified and analyzed areas of human factors concern in nuclear power generation. It reviewed and evaluated current and planned human factors activities and programs throughout industry and the Nuclear Regulatory Commission. The result was a recommended comprehensive human factors plan for the next ten years.

A traditional concurrent verbal protocol method was compared to a heavily cued retrospective verbal protocol in which users were presented with a video tape of their performance to help them recall their thoughts after task completion. The two methods of protocol were employed in a comparison of two different size monitors. Subjects were required to complete 12 tasks which varied in the number of windows required simultaneously on the monitor. The subjects' performance, as measured by steps to completion, task completion time, and errors committed, was compared across monitors and protocol methods. Subjective data were also collected in the form of task difficulty ratings, as well as a global measure of user satisfaction. Verbal data were compared to assess any information differences due to the methods of collection or the monitor sizes.No performance or subjective differences were found between the two protocol methods. The kinds of information gathered were quite different for the two methods, with concurrent protocol subjects giving procedural information and retrospective protocol subjects giving explanations and design statements. Performance data, as well as subjective data, indicated that on tasks that require that one or two windows be present simultaneously, there were no differences between the two monitor sizes. As the number of simultaneous windows increased, however, the large monitor's advantages became apparent. Tasks which require that four windows be present simultaneously were judged to be easier and required fewer steps on the large monitor than on the small monitor.

Three experiments were conducted in which positive and negative contrast on visual display terminals were directly compared. Operator tasks included visual search and reading, with accuracy and timeliness of response measured. In all cases where significant differences exist, better performance was obtained with negative contrast (dark characters or symbols on a lighter background). The increases in performance range from a low of 2.0 percent to a high of 31.6 percent. Based on the above results, we believe that there are significant advantages in visual task performance obtained from the selection of negative contrast displays.Current standards that require negative contrast appear to be justified, while future revisions of ANSI/HFS 100-1988 and other standards should seriously consider incorporating negative contrast as a recommendation or requirement.

This study was conducted to evaluate task performance and subjective preference for two color displays with differing image generation technologies, the standard cathode ray tube shadow mask display and the newer liquid crystal/cathode ray tube display. Six subjects performed three different information processing tasks using each of the two color display technologies and expressed their display preference via evaluation questionnaires. Ambient illumination measurements were obtained to determine optimal conditions for each display. Performance data were obtained as errors per unit task quantity for each of the task types. Subjective evaluations consisted of 5-interval bipolar adjective scales and a forced choice rating. Parametric analyses of the performance measures indicated minor differences between the two display technologies, while nonparametric analyses of the subjective data indicated a preference for the liquid crystal display technology.

This study determined the perceived safety and comfort of an alternating tread stair and a conventional ships ladder. The alternating tread stair and the conventional ships ladder were also compared with respect to travel time and missteps. Subjects in military uniform ascended and descended both the alternating tread stair and the conventional ships ladder under load and no-load conditions. In the load condition subjects performed trials while carrying a 9-kg tool box, and in the no-load condition trials were performed without the tool box. Results indicate that the alternating tread stair is perceived to be safer and more comfortable to use. Moreover, the alternating tread stair had significantly fewer missteps.

The effects of manipulating discrete element error types and font types were determined on a reading performance task using a plasma panel display. Thirty male and 30 female college students attending Virginia Polytechnic Institute and State University participated as subjects. The results demonstrate that reading performance is significantly degraded by the random addition or removal of discrete elements or lines of elements. Subjects made more errors with lower case characters than with upper case characters. Similarly, more errors were also made in the discrete element failure condition than with horizontal line or vertical line failure. The Huddleston font was found to be better than the Lincoln-Mitre and the font used on the HP2621A.

Three competing document production devices were evaluated in terms of ease of learning and ease of use. Forty temporary office workers were hired to learn each device and then perform 16 identical exercises on each machine. After each exercise, the subjects were to rate the features assessed in that exercise along several seven-point rating scales anchored on either “Easy to Do” - “Hard to Do” or “Easy to Remember” - “Hard to Remember.” After completing these exercises on each of the devices, the subjects were then asked to perform six additional exercises on the machines and to compare and rank them.Data consisted of subjective ratings from the exercises, the times required to complete each of the exercises, and the subjective rankings of the machines. Analyses of variance of the subjective ratings identified 78 out of 160 factors by which to distinguish the devices. These subjective factors were supported by an analysis of variance of the time data. Nonparametric analysis of variance of the subjective rankings of the devices identified an additional 23 out of 26 features by which the devices reliably differed.

This report contains the results of two experiments which investigated the effects of the quality of a televised image on eye movements and search-related measures. The first experimental search task involved having subjects perform an air-to-ground search during a simulated flight. The quality of the image presented was varied by either passing, low-pass filtering, or attenuating the video signal and by adding electrical white noise to the video signal. Low to moderate correlations between modulation transfer function area (MTFA) and performance measures generally indicated that as MTFA increases performance improves and fixation durations decrease. The search task of the second experiment consisted of having the subjects search for a designated letter or numeral across a televised picture of randomly positioned letters and numerals. The quality of the picture was varied by either passing, low-pass filtering, high-pass filtering, or attenuating the video signal and by adding electrical white noise to the video signal. Correlations between MTFA and performance measures indicated that increases in MTFA lead to decreases in search time and decreases in fixation duration.

A simulation experiment was performed to determine the effects of TV camera lens field of view and target size upon air-to-ground target recognition via closed-circuit television. Measures of performance were probability of correct target recognition, range of correct recognition, and proportion of errors committed. As the field of view decreased, (1) probability of correct recognition decreased (P < .01), (2) mean range of correct recognition increased (P < .01), (3) errors of commission did not vary (P > .05), and (4) errors of omission increased (P < .01). As target size decreased, (1) probability of correct recognition decreased (P < .01), (2) mean range of correct recognition decreased (P < .01), (3) errors of commission increased (P < .01), and (4) errors of omission increased (P < .01). The increase in mean recognition range with decreases in field of view was greater for large targets than for small targets (P < .05). The field of view had little or no effect upon errors of commission for large targets; however, for small targets, the smaller the field the greater the proportion of errors of commission (P < .01).