Virtual reality (VR) enables immersive, tightly controlled experiments but complicates subjective measurement: moving participants out of the virtual environment (VE) to complete questionnaires changes the measurement context and can increase recall bias. Questionnaires embedded in the VE (INVRQs) enable immediate, time-efficient self-reports and repeated sampling, yet adoption is limited by concerns that INVRQs might bias primary experiential measures and by the implementation burden of usable interfaces. In this within-subject study, 43 participants completed post-task questionnaires using three representative 2D INVRQ interface designs: a body-anchored watch (direct touch), a world-anchored station (handheld pointer), and a world-anchored board at 5 m (laser pointer). Usability and task load differed significantly across interfaces, revealing clear design trade-offs. Interview feedback highlighted corresponding ergonomic themes. In contrast, ratings of presence and flow related to the constant task and VE showed no practically relevant differences across interfaces, supported by equivalence tests. Findings suggest that once basic usability requirements are met, interface choice is unlikely to meaningfully bias experiential measures in similar setups. This study contributes methodological guidance for implementing or selecting INVRQ tools to improve VR study quality, comparability, and reproducibility.
Küntzer et al. (Thu,) studied this question.