The primary motivation for this research was to study the effect of presentation format on acquisition time, recall, and preference. While the main focus was on the relative difference between iconic and textual representations, the independent variables include: presentation format (icon, text and mixed), experience (low, medium, and high), command set (basic, enhanced) and session (primary and secondary recall) . Dependent measures include: acquisition time, response times (primary and secondary recall), and response errors (primary and secondary recall). To assess the presence of functional differences between the independent variables, the ANOVA procedure was applied to each set of dependent measure data. Where appropriate, significant effects were subsequently investigated via application the Newman-Keuls post hoc test procedure. Finally, subject preference measures were correlated with dependent measure data to determine how they were related. The findings associated with each analysis are detailed below. A significant effect was obtained for the main effect of format using acquisition time as the dependent variable. Thus, indicating that acquisition time was influenced by the presentation format of select word processing commands. No other acquisition effects were found to be significant. An ANOVA utilizing response time as the dependent variable supported the hypothesis that presentation format affects average primary response time (p < .01). Additionally, the interaction of the main effects of format and setblock achieved significance (p < .01). Format, setblock and the interaction of the two main effects produce significant (p < .01) average differences in terms of response errors. Therefore, the hypothesis that format and setblock significantly affect the number of response errors was supported. Comparison of the ANOVA summary tables for both response time and errors for primary and secondary tasks indicate that in general, the effects that held significance in the primary recall tasks also achieved (or perhaps more correctly maintained) significance in the secondary recall task. Specifically, using response time as the dependent variable, significance was achieved for the main effects of format (p < .01), and setblock (p < .01), and for the interaction of experience and setblock (p < .05). Finally, using response errors as the dependent variable, the format by setblock interaction was determined to be significant (p < .01). The results support the hypothesis that the number of secondary recall percent correct responses is affected by format and setblock. Subject preference data was utilized to determine the correlation between preference and: average acquisition time, average primary recall response time, average primary recall response errors, average secondary recall response time, and average recall response errors. The correlations achieved indicate that preference is not a particularly useful indicator of performance. In an attempt to summarize the results and findings of the study, the following recommendations/observations are set forth: • With the exception of novices, word processing experience does not dramatically influence the time required to learn or recall stimuli. Similarly, experience does not affect the number of response errors made. • Word processing systems which require subjects to learn and recall exact command sets benefit from enhanced text or enhanced text with graphics. • In applications where a precise verbal response is required, or where differences between functions is subtle, use of an accepted term in conjunction with a graphic is the preferred method. • In general, preference appears to be a poor predictor of performance. Therefore, preference should not be the only basis for deciding on command set formats. However, when subject preference is the primary driver, enhanced text commands should be used. The next preferred approach is the mixed enhanced command set. / Master of Science

The psychophysical method of adjustment was used to determine whether slight changes in load position and comfort could have significant effects on the maximum backpack load acceptable to subjects. Four males and four females, who were accustomed to walking with backpacks, were given 15 minutes to adjust the load until it was, in their judgment, neither too heavy nor too light for an 8-hour trek. The variables in this 2³ within-subject experimental design were horizontal and vertical load position, as well as backpack type. The levels of the horizontal load position differed by a distance of 4.0 cm, which corresponds to the difference between the internal and external-frame backpacks used in the experiment. The vertical distance levels were 1/3 and 2/3 of the height of the pack. The pack types (internal and external-frame) were selected on the basis of their harnesses, to provide two distinct levels of comfort. The results indicated that the horizontal and vertical load positions did not have an appreciable effect on the psychophysically determined maximum acceptable load, although there was a significant interaction between the horizontal position and pack type. There was a significant difference in trunk angle due to Pack type and Horizontal load position. The stride rate was not affected by the treatment conditions, but it decreased significantly with the addition of load. There was a significant difference in comfort ratings between backpacks, with subjects choosing to carry 6% larger loads in the one they rated as more comfortable (the external-frame backpack). / Master of Science

Data collection on isometric forces exerted by means of the digits, is a virtually untapped research area. However, such data would prove particularly useful in areas such as hand-tool and control design, and also in medical evaluation. A standardized protocol is necessary if a sound, useful data base is to be built. This study developed such a protocol and data were collected using the defined protocol. The study also showed that occupational level (defined by tools and controls used) and gender both had significant effects on certain strength exertions of the digits. Therefore the appropriate data must be collected, depending on the intended use and user population. Regression equations were produced which predicted the strength exertions using anthropometric measurements which are commonly available. Although some particular exertions were not well predicted, the potential of prediction was verified. / Master of Science

The Assistance Manager, one of the tools of the Simulation Model Development Environment (SMDE), is required to provide assistance to a user during the process of model development. This thesis describes the research effort to prototype the SMDE Assistance Manager. Requirements are set forth and a design is established for the Assistance Manager prototype. The implementation is described, and the Assistance Manager is shown to provide a highly flexible interface between the user and the database of assistance information. Assessment criteria are established, and the prototype is evaluated. Results of the evaluation indicate that the Assistance Manager incorporates the characteristics considered desirable in online assistance systems, and serves as a basis for future enhancement and development. / Master of Science

This research was part of a program sponsored by the Army Electronics Research and Development Command. The program goals are to develop a generic input/output device based on a 4- x 8-in electroluminescent flat panel display coupled with a touch sensitive input device. The primary purpose of this dissertation was to evaluate the six major manufacturers' implementation of the three most common technologies for touch screens. The evaluation was based on operator performance. The three technologies represented in the research were IR beam matrix switches, conductive membrane switches, and transparent capacitance switches. A secondary goal of the research was to establish a link between measurable hardware parameters of any touch sensitive device (TSO) and operator performance. These parameters were then used to build models of operator performance under a variety of conditions. The primary goal of technology evaluation was approached through two experiments based on two generic types of tasks typical of current and expected TSD applications. These experiments compared six different TSDs from different manufacturers across varying conditions of lighting, viewing angle, and touch target dimensions. The secondary goal of TSD performance modeling was accomplished through careful measurement of many image quality and touch sensing characteristics of the six TSDs and subsequent construction of stepwise linear regression models of user performance. These models were built using the performance data collected in the first part of the evaluation. Results from the performance comparison revealed that across tasks and conditions, one device of the IR beam technology was found to be the best performer. Another device of the same technology was equivalent in reading aspects of performance but inferior with respect to touch inputting performance. This performance difference was hypothesized to be due to differences between these two devices in touch sensor parallax. The linear regression modeling effort resulted in the identification of several hardware parameters which are important to TSD user performance. Additionally, models of performance under specific conditions were developed which accounted for most of the variation observed in the performance data. / Ph. D.

The Dialogue Management System (DMS), the setting for this research, is a system for designing, implementing, testing, and modifying interactive human-computer systems. As in the early stages of software engineering development, current approaches to human-computer interface design are ad hoc, unstructured, and incomplete. The primary goal of this research has been to develop a structural, descriptive, language-oriented model of human-computer interaction, based on a theory of human-computer interaction. This model is a design and implementation model, serving as the framework for a dialogue engineering methodology for human-computer interface design and interactive tools for human-computer interface implementation. This research has five general task areas, each building on the previous task. The theory of human-computer interaction is a characterization of the inherent properties of human-computer interaction. Based on observations of humans communicating with computers using a variety of interface types, it addresses the fundamental question of what happens when humans interact with computers. Formalization of the theory has led to a muIti-dimensional dialogue transaction model, which encompasses the set of dialogue components and relationships among them. The model is based on three traditional levels of language: semantic, syntactic, and lexical. Its dimensions allow tailoring of an interface to specific states of the dialogue, based on the sequence of events that might occur during human-computer interaction. This model has two major manifestations: a dialogue engineering methodology and a set of interactive dialogue implementation tools. The dialogue engineering methodology consists of a set of procedures and a specification notation for the design of human-computer interfaces. The interactive dialogue implementation tools of AIDE provide automated support for implementing human-computer interfaces. The AIDE interface is based on a "what you see is what you get" concept, allowing the dialogue author to implement interfaces without writing programs. Finally, an evaluation of work has been conducted to determine its efficacy and usefulness in developing human-computer interfaces. A group of subject dialogue authors using AIDE created and modified a prespecified interface in a mean time of just over one hour, while a group of subject application programmers averaged nearly four hours to program the identical interface. Theories, models, methodologies, and tools such as those addressed by this research promise to contribute greatly to the ease of production and evaluation of human-computer interfaces. / Ph. D.

This dissertation investigated the effects of age on performance and image quality rating while varying screen surface treatment, ambient lighting, and character resolution. Five age groups were included, ranging from 18 to 69 years of age. The study used a factorial design to vary seven surface treatments which either reduced glare, enhanced contrast, or both; three lighting conditions, dark, diffuse, and specular; and two character resolutions, high and low, subtending visual angles of 16.1 arcmin. and 32.2 arcmin. respectively. Performance was measured using both a speed of reading task and a search task. In addition, subjects rated the image quality of displayed characters within each filter, lighting, resolution condition using a list of nine adjectives. Results showed performance times to increase with age. The older age groups (40-49, 50-59, 60-69) performed better with the quarterwave filter, which enhanced contrast and reduced glare, and most poorly with the filters with the harshest etch (Gloss25) and the lowest transmission (31%). Performance was significantly slower for specular and dark lighting. A finding consistent with previous research indicated that extremely high luminance contrast degrades performance with low room illumination. Finally, for all conditions in which resolution was a factor performance was fastest and ratings were highest with the low resolution characters. / Ph. D.

An isometric, zero-order, two-dimensional pursuit tracking task utilizing a tracking path that incorporated both linear and circular segments was used to examine the effects of variation in force magnitude, force direction, and direction of target movement upon tracking performance. A contralateral force-matching procedure was also employed to assess the effects of variation in force level and force direction upon force discrimination capabilities. Increases in force demand were hypothesized to result in degradation of both force discrimination capabilities and accuracy of tracking performance. Variation in force direction was hypothesized to result in tracking performance degradation and force discrimination deterioration that were inversely related to strength-related differences associated with each direction. It was hypothesized that linear tracking performance during inward (force-decreasing) movement of the target would be superior to linear tracking performance in the outward (force-increasing) direction. Finally, it was hypothesized that the direction-sensitive strength:demand ratio, SDR, (a measure of the relationship between strength and the magnitude of force demand) would correlate with both tracking performance and force discrimination measures and that force discrimination measures would correlate with tracking performance. The findings robustly supported the hypothesized Force Level effect. The strength-related Force Direction effects were also supported, but somewhat less consistently than those for Force Level. As also hypothesized, linear inward tracking was superior to linear outward tracking. Previously unreported direction-of-movement effects were found for the circular tracking conditions. When measured along the path, clockwise (CW) tracking was superior to counterclockwise (CCW) tracking with the differences being greatest at the higher force level and in the longitudinal (forward and aft) directions. CCW tracking was superior to CW tracking when measured orthogonal to path. The hypothesized correlations among SDR, two of the three force discrimination measures, and tracking performance were found to be small but significant. / Ph. D.

The purpose of this study was to determine the extent specific ergonomic factor implementations in computer and video display terminal (VDT) installations for student use in middle school classrooms. The data interpretations using existing furniture without modification or adaptation. Of all the seating observed, 75% of the seating met standards for middle school students. Keyboards and video display screens had been placed on existing tables and were all higher than ergonomically desirable for middle school students or adults.

Call number: LD2668 .T4 1978 B42 / Master of Science