Can People Not Tell Left from Right in VR? Point-to-origin Studies Revealed Qualitative Errors in Visual Path Integration Bernhard E. Riecke ∗ Jan M. Wiener † Max Planck Institute for Biological Cybernetics, Tübingen, Germany ABSTRACT Even in state-of-the-art virtual reality (VR) setups, participants of- ten feel lost when navigating through virtual environments. In psy- chological experiments, such disorientation is often compensated for by extensive training. The current study investigated partici- pants’ sense of direction by means of a rapid point-to-origin task without any training or performance feedback. This allowed us to study participants’ intuitive spatial orientation in VR while mini- mizing the influence of higher cognitive abilities and compensatory strategies. After visually displayed passive excursions along one- or two-segment trajectories, participants were asked to point back to the origin of locomotion "as accurately and quickly as possible". Despite using a high-quality video projection with a 84 ◦ × 63 ◦ field of view, participants’ overall performance was rather poor. More- over, six of the 16 participants exhibited striking qualitative errors, i.e., consistent left-right confusions that have not been observed in comparable real world experiments. Taken together, this study sug- gests that even an immersive high-quality video projection system is not necessarily sufficient for enabling natural spatial orientation in VR. We propose that a rapid point-to-origin paradigm can be a useful tool for evaluating and improving the effectiveness of VR setups in terms of enabling natural and unencumbered spatial ori- entation and performance. Keywords: ego-motion simulation, human factors, navigation, point-to-origin, psychophysics, spatial orientation, spatial updating, triangle completion, Virtual Reality. Index Terms: H.1.2 [Models and Principles]: User/Machine Systems—Human factors, Human information processing; H.5.1 [Information Interfaces and Presentation, (e.g. HCI]: Multimedia Information Systems—Artificial, augmented, and virtual realities; J.4 [Social and Behavioral Sciences]: Psychology 1 I NTRODUCTION Most modern Virtual Reality (VR) simulators suffer from a grave malady: Severe disorientation [5, 8, 17, 27]. This strong tendency to easily get lost when navigating in VR can be overcome if people (a) are allowed to physically perform the simulated actions (e.g., though physical walking or at least turning [4, 13, 11, 10, 37], (b) are provided with useful visual landmarks or a well-known visual scene [4, 10, 24, 25], and/or (c) are given sufficient time to employ higher cognitive processes like mental spatial reasoning and/or re- ceive extensive feedback training on the task [7, 12, 24, 35]. This stands in striking contrast to the real world, where spatial orientation and spatial updating typically operate automatically and effortlessly, requiring few if any cognitive resources [6, 19, 26]. Thus, most VR simulation paradigms do not empower people to use their “normal”, evolutionary-developed spatial orientation abil- ities. Instead, VR users often seem to resort to cognitively more ∗ e-mail: bernhard.riecke@tuebingen.mpg.de † e-mail: jan.wiener@college-de-france.fr demanding and computationally more expensive strategies. This might be related to the lack of robust and effortless spatial updating observed in many VR situations. In order to determine what critical aspects of the real world are not being captured in modern VR systems, we developed an exper- imental paradigm that mitigates the influence of higher cognitive abilities and strategies. There are two main elements to the exper- imental paradigm. First, a simple and ecologically plausible task is used – rapid pointing to the origin of locomotion after visu- ally displayed passive excursions consisting of a linear translation, a subsequent rotation, and, in some cases, a second linear transla- tion. In a way, one could picture this task as providing the indication of a “homing vector” that points from the current position and ori- entation back to the starting position [13, 11]. When performed in the real world using physical walking, pointing back to the origin of travel after one- or two-segment excursions is usually perceived as quite easy and not requiring much cognitive effort or computation- ally demanding strategies, even when performed with limited or no visual cues [10, 28, 30]. Using a rapid pointing paradigm has the strong advantage that it neither provides the time nor the feedback necessary to develop or use higher cognitive abilities (e.g., spatial reasoning) or strategies [25]. It is important to note that participants in the present study never received any performance feedback. Sec- ond, by presenting only optic flow information using a uniformly textured ground plane, visual landmarks and other navigation aids are eliminated from the virtual environment, further restrict- ing the possible influence of high-level strategies. Rapid pointing after simple excursion paths is quite trivial to per- form in the real world, even when all visual and auditory spatial cues and landmarks are excluded (e.g., using blindfolds and head- phones displaying broad-band noise). Due to an “automatic spatial updating” of our egocentric mental spatial representation of our im- mediate surroundings while walking, we maintain a natural and in- tuitive knowledge of where we are with respect to the environment during shorter periods of travel [6, 19, 26]. When visual and audi- tory cues are excluded, vestibular, proprioceptive, and kinaesthetic cues are still sufficient for enabling automatic spatial updating. We may not be perfectly accurate and precise due to accumulating path integration errors during the locomotion, but the task is relatively easy to perform in the sense that it does not require noticeable cog- nitive effort – we just seem to automatically “know” where we are with respect to immediate objects of interest. This is typically re- flected in the subjective ease of performing the task, a minimal cog- nitive load, a lack of qualitative errors like left/right reversals, and rather short overall response times (typically below 2s) with little or no dependence on the angle turned or distance traveled [6, 26]. When comparable tasks are performed in a virtual environment where only path-integration based visual cues (optic flow) are pro- vided and participants are not allowed to physically move, overall response errors increase and participants typically think more be- fore responding [4, 10, 7, 18]. For simple spatial orientation tasks like triangle completion or estimation of turning angles, both sys- tematic and variable errors seem to depend considerably on the display device used, with head-mounted displays and flat projec- tion screens yielding the largest systematic and random errors, and large, curved projection screens yielding the lowest errors