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Direct perception, as part of the ecological approach to perception, defines a relationship between an organism and their environment that is specified by lawful information. Researchers can apply the ecological approach to eXtended Reality (XR) work to obtain a richer understanding of users’ perception-action coordination in novel virtual settings. To encourage widespread adoption of this theoretical framework, this methodological paper introduces four major concepts from the ecological approach that are highly relevant to XR applications. We also provide an overview of existing literature to illustrate how those concepts may be used to inform and test their designs. These elements include the study of calibration and attunement, affordances, action based responses, and intrinsic scaling for measurements. The goal of this work is to increase awareness of the value of the ecological approach, and to provide a practical, evidence-based reference for researchers interested in applying these techniques in XR research. 

Interpupillary distance (IPD) is the most important parameter for creating a user-specific stereo parallax, which in turn is crucial for correct depth perception. This is why contemporary Head-Mounted Displays (HMDs) offer adjustable lenses to adapt to users’ individual IPDs. However, today’s Video See-Through Augmented Reality (VST AR) HMDs use fixed camera placements to reconstruct the stereoscopic view of a user’s environment. This leads to a potential mismatch between individual IPD settings and the fixed Inter-Camera Distances (ICD), which can lead to perceptual incongruencies, limiting the usability and, potentially, the applicability of VST AR in depth-sensitive use cases. To investigate this incongruency between IPD and ICD, we conducted a 2 × 3 mixed-factor design user study using a near-field, open-loop reaching task comparing distance judgments of Virtual Reality (VR) and VST AR. We also investigated changes in reaching performance via perceptual calibration by incorporating a feedback phase between pre- and post-phase conditions, with a particular focus on the influence of IPD-ICD differences. Our Linear Mixed Model (LMM) analysis showed a significant difference between VR and VST AR, an effect of IPD-ICD mismatch, and a combined effect of both factors. However, subjective measures showed no effect underlining the subconscious nature of the perception of VST AR. This novel insight and its consequences are discussed specifically for depth perception tasks in AR, eXtended Reality (XR), and potential use cases. 

Redirected walking techniques use rotational gains to guide users away from physical obstacles as they walk in a virtual world, effectively creating the illusion of a larger virtual space than is physically present. Designers often want to keep users unaware of this manipulation, which is made possible by limitations in human perception that render rotational gains imperceptible below a certain threshold. Many aspects of these thresholds have been studied, however no research has yet considered whether these thresholds may change over time as users gain more experience with them. To study this, we recruited 20 novice VR users (no more than 1 hour of prior experience with an HMD) and provided them with an Oculus Quest to use for four weeks on their own time. They were tasked to complete an activity assessing their sensitivity to rotational gain once each week, in addition to whatever other activities they wanted to perform. No feedback was provided to participants about their performance during each activity, minimizing the possibility of learning effects accounting for any observed changes over time. We observed that participants became significantly more sensitive to rotation gains over time, underscoring the importance of considering prior user experience in applications involving rotational gain, as well as how prior user experience may affect other, broader applications of VR. 

This work explored how users’ sensitivity to offsets in their avatars’ virtual hands changes as they gain exposure to virtual reality. We conducted an experiment using a two-alternative forced choice (2-AFC) design over the course of four weeks, split into four sessions. The trials in each session had a variety of eight offset distances paired with eight offset directions (across a 2D plane). While we did not find evidence that users became more sensitive to the offsets over time, we did find evidence of behavioral changes. Specifically, participants’ head-hand coordination and completion time varied significantly as the sessions went on. We discuss the implications of both results and how they could influence our understanding of long-term calibration for perception-action coordination in virtual environments.