Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 139-150). Also available via the Internet.

A study was conducted to investigate the effects of certain cinematic choices on people’s ability to judge the posture of the wrist from video images. Deviated wrist postures, which are associated with the performance of many tasks, have been reported to play a role in hand and arm discomfort and in a variety of disorders. The goal of this study was to gain a better understanding of people’s performance in judging wrist posture as well as people’s ability to judge their performance. One objective was to determine the relative performance effects of one still image, two still images, and full-motion images. Other objectives were to determine the effect on performance relative to three different views and ten different wrist positions. It was also of interest to begin to understand how these three independent factors may interact with one another and also how the three dependent variables-accuracy, certainty, and decision time-related to one another. A second experiment also investigated the display effects of a single still image vs. full-motion video. A second factor that was investigated was the performance effects of more complex hand positions (i.e., while holding objects and performing real tasks). In the first Experiment it was found that a view which was normal to the thumb-side of the hand resulted in significantly better performance than a view oblique to the hand. This effect held for each of the Display Methods and for seven of the ten wrist positions. It was hypothesized that this effect may be due to the inherent superiority of one view over another. An alternative possibility is that the thumb-side view offered participants the opportunity to compare what they saw on the screen to their own hands. It was suggested that these alternative possibilities be tested as the results may either support efforts to find “the best view” or to develop ways to provide “comparison postures.” In the first experiment there were significant main and interaction effects for the dependent variable, accuracy. There were also significant main effects found for certainty and decision time, but no interaction effects were found. An interesting finding from the first experiment was that people were generally overly confident of their performance. In most instances, participants’ performances were not related to their perceived performances. For the full-motion images, half of the participants’ perception of their performance was negatively correlated with actual performance. As would be expected, two views were generally found to be better than one view. However, it was also found that a particular single view (thumb-side) resulted in a level of performance that was not significantly different from two-still combinations which did not include the thumb-side view. No significant effects were found for the second experiment and the levels of performance were found to be similar to the first experiment under the oblique view condition. As a background to the experimental investigations, literature pertaining to these four areas was reviewed: The relationship of wrist posture to hand and arm disorders, methods of observing posture, advancements in video technology, and considerations regarding the nature of video as a two-dimensional display format. Also explored were differences in public perception about the task-related “causes” of hand and arm disorders vs. the clinical and observational findings that were reviewed. It was suggested that the ergonomic community bears some responsibility for these differences. Better methods are needed not only to observe human factors, but also to communicate our observations amongst ourselves, to other professionals, and to anyone who could benefit by such knowledge. / Master of Science