A software agent is a computer program that operates within computing environments. The owners of software agents may instruct their agents to roam the networks, access desired information by exchanging data with other agents or people, and handle business and personal transactions. As the interactions between software agents and humans become more frequent, it is relevant to ask whether there are any issues of law that may guide their interactions and conduct. For example, as the agents become more intelligent and autonomous, who will be responsible for the mistakes that software agents make? Will software agents be allowed to contract with humans and with each other, and if so will such contracts be enforceable? And, will software agents have standing to sue and be sued? While there are a host of legal issues associated with software agents operating within virtual environments, the main issue addressed in this paper is whether software agents should be granted the legal rights associated with personhood. After discussing basic characteristics of software agents, and personhood in general, the paper concludes by outlining three possible scenarios that could represent the legal status of software agents in the future; these include the current status quo of property, the status of an indentured servant, and the status and associated rights of legal personhood.

This paper describes a study on the sense of presence and task performance in a virtual environment as affected by copresence (one subject working alone versus two subjects working as partners), level of control (control of movement and control of navigation through the virtual environment), and head tracking. Twenty subjects navigated through six versions of a virtual environment and were asked to identify changes in locations of objects within the environment. After each trial, subjects completed a questionnaire designed to assess their level of presence within the virtual environment. Results indicated that collaboration did not increase the sense of presence in the virtual environment, but did improve the quality of the experience in the virtual environment. Level of control did not affect the sense of presence, but subjects did prefer to control both movement and navigation. Head tracking did not affect the sense of presence, but did contribute to the spatial realism of the virtual environment. Task performance was affected by the presence of another individual, by head tracking, and by level of control, with subjects performing significantly more poorly when they were both alone and without control and head tracking. In addition, a factor analysis indicated that questions designed to assess the subjects' experience in the virtual environment could be grouped into three factors: (1) presence in the virtual environment, (2) quality of the virtual environment, and (3) task difficulty.

This paper proposes a model of interaction in virtual environments which we term the immersion, presence, performance (IPP) model. This model is based on previous models of immersion and presence proposed by Barfield and colleagues and Slater and colleagues. The IPP model describes the authors' current conceptualization of the effects of display technology, task demands, and attentional resource allocation on immersion, presence, and performance in virtual environments. The IPP model may be useful for developing a theoretical framework for research on presence and for interpreting the results of empirical studies on the sense of presence in virtual environments. The model may also be of interest to designers of virtual environments.

This study investigated performance in a desktop virtual environment as a function of stereopsis and head tracking. Ten subjects traced a computer-generated wire using a virtual stylus that was slaved to the position of a real-world stylus tracked with a 6-DOF position sensor. The objective of the task was to keep the virtual stylus centered on the wire. Measures collected as the subjects performed the task were performance time, and number of times the stylus overstepped the virtual wire. The time to complete the wire-tracing task was significantly reduced by the addition of stereopsis, but was not affected by the presence of head tracking. The number of times the virtual stylus overstepped the wire was significantly reduced when head-tracking cues were available, but was not affected by the presence of stereoscopic cues. Implications of the results for performance using desktop virtual environments are discussed.

This paper reports the results of three studies, each of which investigated the sense of presence within virtual environments as a function of visual display parameters. These factors included the presence or absence of head tracking, the presence or absence of stereoscopic cues, and the geometric field of view used to create the visual image projected on the visual display. In each study, subjects navigated a virtual environment and completed a questionnaire designed to ascertain the level of presence experienced by the participant within the virtual world. Specifically, two aspects of presence were evaluated: (1) the sense of “being there” and (2) the fidelity of the interaction between the virtual environment participant and the virtual world. Not surprisingly, the results of the first and second study indicated that the reported level of presence was significantly higher when head tracking and stereoscopic cues were provided. The results from the third study showed that the geometric field of view used to design the visual display highly influenced the reported level of presence, with more presence associated with a 50 and 90° geometric field of view when compared to a narrower 10° geometric field of view. The results also indicated a significant positive correlation between the reported level of presence and the fidelity of the interaction between the virtual environment participant and the virtual world. Finally, it was shown that the survey questions evaluating several aspects of presence produced reliable responses across questions and studies, indicating that the questionnaire is a useful tool when evaluating presence in virtual environments.

Two studies were performed to investigate the sense of presence within stereoscopic virtual environments as a function of the addition or absence of auditory cues. The first study examined the presence or absence of spatialized sound, while the second study compared the use of nonspatialized sound to spatialized sound. Sixteen subjects were allowed to navigate freely throughout several virtual environments and for each virtual environment, their level of presence, the virtual world realism, and interactivity between the participant and virtual environment were evaluated using survey questions. The results indicated that the addition of spatialized sound significantly increased the sense of presence but not the realism of the virtual environment. Despite this outcome, the addition of a spatialized sound source significantly increased the realism with which the subjects interacted with the sound source, and significantly increased the sense that sounds emanated from specific locations within the virtual environment. The results suggest that, in the context of a navigation task, while presence in virtual environments can be improved by the addition of auditory cues, the perceived realism of a virtual environment may be influenced more by changes in the visual rather than auditory display media. Implications of these results for presence within auditory virtual environments are discussed.

Currently, the hardware to produce virtual environments does not include olfactory displays, in spite of the fact that a wealth of sensory information is available from the olfactory sense. This paper reviews the physiological and psychological aspects of olfaction and discusses the use of olfactory displays for virtual environments. Further, it outlines the information that will be needed by the virtual environment research community to integrate olfactory stimuli into virtual environments.

This paper presents the results of three surveys that compared the human's ability to detect and discriminate visual, auditory, tactile, and kinesthetic information with current technical specifications of virtual environment equipment. The comparison exposes limitations of current virtual environment interfaces and thus indicates areas where improvements in equipment design are needed. Furthermore, the paper presents basic definitions and units of measurement for sensory modalities, which also can be used to describe the capabilities of virtual environment equipment. Finally, the paper concludes with remarks concerning the relationship between the data presented in the three surveys and the design of virtual interfaces.