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In this research, an approach is proposed for the robust tracking of upper body movement in unconstrained environments by using a Haar- Disparity algorithm together with a novel 2D silhouette projection algorithm. A cascade of boosted Haar classifiers is used to identify human faces in video images, where a disparity map is then used to establish the 3D locations of detected faces. Based on this information, anthropometric constraints are used to define a semi-spherical interaction space for upper body poses. This constrained region serves the purpose of pruning the search space as well as validating user poses. Haar-Disparity improves on the traditional skin manifold tracking by relaxing constraints on clothing, background and illumination. The 2D silhouette projection algorithm provides three orthogonal views of the 3D objects. This allows tracking of upper limbs to be performed in the 2D space as opposed to manipulating 3D noisy data directly. This thesis also proposes a complete optimal set of interactions for very large interactive displays. Experimental evaluation includes the performance of alternative camera positions and orientations, accuracy of pointing, direct manipulative gestures, flag semaphore emulation, and principal axes. As a minor part of this research interest, the usability of interacting using only arm gestures is also evaluated based on ISO 9241-9 standard. The results suggest that the proposed algorithm and optimal set of interactions are useful for interacting with large displays.

This item is not the definitive copy. Please use the following citation when referencing this material: Dillon, A. (1990) The human factors of hypertext. International Forum on Information and Documentation, 15(4), 32-38. Abstract: The present paper reviews the human factors issues pertinent to the design and use of hypertext documents. It is argued that many of the claims for the new medium are based largely on subjective impressions of its advocates rather than empirical demonstrations of its advantages. Hypertext applications are presented here as a structured subset of an information world that the user can access though an interface. Research relevant to all aspects of reading from screens is reviewed and conclusions for the development of more usable electronic documents are presented. Postscript: Many of the arguments expressed in this paper are dealt with in much more detail in the book Hypertext in Context, by C. McKnight, A. Dillon and J. Richardson. (1991) published by Cambridge University Press.

The purpose of this research was to provide evidence to support specific features of a software user interface implementation. A 3 x 2 x 2 full factorial, between subjects design was employed, in a laboratory experiment systematically varying existence or non-existence of a user interface and media of help documentation (either online or written), while blocking for varying levels of user experience. Subjects completed a set of tasks using a computer, so the experimenters could collect and evaluate various performance and attitudinal measures. Several attitudinal measures were developed and validated as part of this research. Consistent with previous findings, this research found that a user's previous level of experience in using a computer had a significant impact on their performance measures. Specifically, increased levels of user experience were associated with reduced time to complete the tasks, fewer number of characters typed, fewer references to help documentation, and fewer requests for human assistance. In addition, increased levels of user experience were generally associated with higher levels of attitudinal measures (general attitude toward computers and satisfaction with their experiment performance). The existence of a user interface had a positive impact on task performance across all levels of user experience. Although experienced users were not more satisfied with the user interface than without it, their performance was better. This contrasts with at least some previous findings that suggest experienced users are more efficient without a menu-driven user interface. The use of online documentation, as opposed to written, had a significant negative impact on task performance. Specifically, users required more time, made more references to the help documentation, and required more human assistance. However, these users generally indicated attitudinal measures (satisfied) that were as high with online as written documentation. There was a strong interaction between the user interface and online documentation for the task performance measures. This research concludes that a set of tasks can be performed in significantly less time when online documentation is facilitated by the presence of a user interface. Written documentation users seemed to perform equivalently with or without the user interface. With online documentation the user interface became crucial to task performance. Research implications are presented for practitioners, designers and researchers.

Current research in screen design for human computer interaction has demonstrated that user task performance is influenced by placement, prompting methodology, and screen complexity. To assess the difference between a grouped item screen prompt and a series of single item screen prompts, a field experiment in a semiconductor manufacturing facility was designed. Subjects were randomly assigned to one of two groups to use a data entry system. Seven of the screen prompts differed between the two groups. During the four weeks of the study, a significant difference was measured between groups. The group screen users had lower task times for all four weeks. No significant correlation exists between work experience, performance review scores, or designated work shift. A strong negative correlation exists between frequency of system usage and task time. No difference was noted for measured errors. Subjective scores significantly favored the group screen design.

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