Measuring Tool Embodiment: Virtual vs. Physical Tools

Person holding a grabber in front of computer screen

The current research in human-computer interaction (HCI) focuses on using performance measures or self-reports questionnaires to evaluate interactive technologies. Research in psychology and philosophy, on the other hand, provides an understanding of the human condition in the physical environment. Consequently, the aim of this dissertation is to provide an effective methodology to measure the invisibility aspect of technology that applies both experimental psychology and HCI research. Study one presented in this dissertation used the after-effect phenomenon as a measure of object embodiment — when interacting with physical objects can affect haptic changes in perception. Study two investigated tool embodiment to measure the interaction with physical and virtual tools, where change in attention was used as a measure of tool embodiment. Finally, study three further examined tool embodiment with different tool states (broken or working tool) and different inputs alternatives.

Over the past decade, multi-touch surfaces have become commonplace, with many researchers and practitioners describing the benefits of their natural, physical-like interactions. Study one presents an empirical investigation of the psychophysical effects of direct interaction with both physical and virtual objects. 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, was used as a measure. While this effect is robustly reproducible when using physical artefacts, this same effect does not manifest when manipulating virtual objects on a direct, multi-touch tabletop display.

Study two leveraged the phenomenon of tool embodiment as measure of interaction. Tool embodiment is when a tool becomes an extension of one’s body, where attention shifts to the task at hand, rather than the tool itself. This study tested tool embodiment framework to measure the aspect of being part of a tool by incorporating philosophical and psychological concepts. This framework was applied to design and conduct study two that uses attention to measure readiness-to-hand with both a physical tool and a virtual tool. 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 was introduced in this study. The results demonstrated that participants paid more attention to the task than to both virtual and physical tools.

Study three further investigated tool embodiment to measure ready-to-hand and unready-to-hand situations. Locus of attention index (LAI) was used to measure the level of tool embodiment in virtual environments. Three different input modalities were used to control the virtual tool to accomplish the task. The results of this study showed that the LAI is higher with the working tool indicating an increased level of tool embodiment, and lower with broken tool indicating a decreased level of tool embodiment.

Overall, the research presented in this dissertation investigated embodied interactions with both physical and virtual environments. The contributions included the construction of an evolution measure of object interaction (using the measure of after effect with physical and virtual tools) and tool interaction (using the measure of attention and LAI with physical and virtual tools). The empirical results of study one revealed that the after-effect measure might not be a practical measure to evaluated embodied interactions in virtual environments. However, study two and three provided a reliable method to measures embodied interactions when using tools to interact with the virtual environments. This dissertation also provided tool embodiment framework that can be used as a guide for designers to evaluate the invisibility aspect of technology.