Virtual reality (VR) strives to replicate the sensation of the physical environment by mimicking people's perceptions and experience of being elsewhere. These experiences are of-ten mediated by the objects and tools we interact with in the virtual world (e.g., a controller). Evidence from psychology posits that when using the tool proficiently, it becomes em-bodied (i.e., an extension of one's body). There is little work,however, on how to measure this phenomenon in VR, andon how different types of tools and controllers can affect the experience of interaction. In this work, we leverage cognitive psychology and philosophy literature to construct the Locus-of-Attention Index (LAI), a measure of tool embodiment. We designed and conducted a study that measures readiness-to-hand and unreadiness-to-hand for three VR interaction techniques: hands, a physical tool, and a VR controller. The study shows that LAI can measure differences in embodiment with working and broken tools and that using the hand directly results in more embodiment than using controllers.

New interaction techniques, like multi-touch, tangible interaction, and mid-air gestures often promise to be more intuitive and natural; however, there is little work on how to measure these constructs. One way is to leverage the phenomenon of tool embodiment---when a tool becomes an extension of one's body, attention shifts to the task at hand, rather than the tool itself. In this work, we constructed a framework to measure tool embodiment by incorporating philosophical and psychological concepts. We applied this framework to design and conduct a study that uses attention to measure readiness-to-hand with both a physical tool and a virtual tool. We introduce a novel task where participants use a tool to rotate an object, while simultaneously responding to visual stimuli both near their hand and near the task. Our results showed that participants paid more attention to the task than to both kinds of tool. We also discuss how this evaluation framework can be used to investigate whether novel interaction techniques allow for this kind of tool embodiment.

Over the past decade, multi-touch surfaces have become commonplace, with many researchers and practitioners describing the benefits of their natural, physical-like interactions. We present a pair of studies that empirically investigates the psychophysical effects of direct interaction with both physical and virtual artefacts. We use the phenomenon of Kinesthetic Figural After Effects-a change in understanding of the physical size of an object after a period of exposure to an object of different size. Our studies show that, while this effect is robustly reproducible when using physical artefacts, this same effect does not manifest when manipulating virtual artefacts on a direct, multi-touch tabletop display. We contribute quantitative evidence suggesting a psychophysical difference in our response to physical vs. virtual objects, and discuss future research directions to explore measurable phenomena to evaluate the presence of physical-like changes from virtual on-screen objects.