{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:41:43Z","timestamp":1760060503523,"version":"build-2065373602"},"reference-count":54,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,8,29]],"date-time":"2025-08-29T00:00:00Z","timestamp":1756425600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Virtual Worlds"],"abstract":"<jats:p>Natural walking locomotion in virtual reality (VR) allows intuitive movement through a virtual environment (VE), lower rates of simulator sickness, and increased immersion. However, it is limited by available play-space. Impossible spaces are VEs that use self-overlapping geometry to imitate larger play-spaces within a smaller area. Understanding how users interact with impossible spaces requires understanding how they perceive and remember VEs. However, it is unknown how impossible spaces impact users\u2019 memory. An experiment was conducted comparing 32 participants\u2019 memory from two conditions: natural walking in an impossible space and joystick movement in a similar non-impossible space. Participants were given up to 20 min to explore a virtual museum and were not instructed on what to remember. The experience was designed to allow participants to freely explore the VE at their own pace, allowing engagement duration to vary naturally. No significant differences were found between conditions for object or spatial memory; however, participants in the natural walking condition spent more time in the environment, revisited more areas, and were more confident identifying objects not encountered in the VE. This suggests natural walking in impossible spaces may be a viable alternative to traditional locomotion techniques.<\/jats:p>","DOI":"10.3390\/virtualworlds4030039","type":"journal-article","created":{"date-parts":[[2025,8,29]],"date-time":"2025-08-29T12:25:57Z","timestamp":1756470357000},"page":"39","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Now You\u2019re Thinking with Portals: Investigating Episodic Memory and Locomotion with Redirected Walking in Impossible Spaces"],"prefix":"10.3390","volume":"4","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-8049-3224","authenticated-orcid":false,"given":"Samuel E. R.","family":"Thompson","sequence":"first","affiliation":[{"name":"Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-0888-3490","authenticated-orcid":false,"given":"Dominik","family":"Lange-Nawka","sequence":"additional","affiliation":[{"name":"School of Computer Science, University of Auckland, Auckland 1142, New Zealand"}]},{"given":"Aidan","family":"Habedank","sequence":"additional","affiliation":[{"name":"School of Computer Science, University of Auckland, Auckland 1142, New Zealand"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-0947-1648","authenticated-orcid":false,"given":"Jonathan","family":"Lau","sequence":"additional","affiliation":[{"name":"School of Computer Science, University of Auckland, Auckland 1142, New Zealand"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-5303-1925","authenticated-orcid":false,"given":"Craig Russel","family":"Anderson","sequence":"additional","affiliation":[{"name":"School of Computer Science, University of Auckland, Auckland 1142, New Zealand"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8013-4118","authenticated-orcid":false,"given":"Burkhard C.","family":"W\u00fcnsche","sequence":"additional","affiliation":[{"name":"School of Computer Science, University of Auckland, Auckland 1142, New Zealand"}]}],"member":"1968","published-online":{"date-parts":[[2025,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Di Luca, M., Seifi, H., Egan, S., and Gonzalez-Franco, M. (2021, January 8\u201313). Locomotion vault: The extra mile in analyzing vr locomotion techniques. Proceedings of the 2021 CHI Conference on Human Factors in Computing Systems, Jokohama, Japan.","DOI":"10.1145\/3411764.3445319"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"555","DOI":"10.1109\/TVCG.2012.47","article-title":"Impossible spaces: Maximizing natural walking in virtual environments with self-overlapping architecture","volume":"18","author":"Suma","year":"2012","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Neerdal, J.A., Hansen, T.B., Hansen, N.B., Bonita, K.L.F., and Kraus, M. (2019, January 6\u20138). Navigating procedurally generated overt self-overlapping environments in VR. Proceedings of the International Conference on ArtsIT, Interactivity and Game Creation, Aalborg, Denmark.","DOI":"10.1007\/978-3-030-53294-9_17"},{"key":"ref_4","unstructured":"Auda, J., Gruenefeld, U., and Schneegass, S. (May, January 29). If the map fits! Exploring minimaps as distractors from non-euclidean spaces in virtual reality. Proceedings of the CHI Conference on Human Factors in Computing Systems Extended Abstracts, New Orleans, LA, USA."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Warren, W.H. (2019). Non-euclidean navigation. J. Exp. Biol., 222.","DOI":"10.1242\/jeb.187971"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Lochner, D.C., and Gain, J.E. (2021, January 10\u201312). VR Natural Walking in Impossible Spaces. Proceedings of the 14th ACM SIGGRAPH Conference on Motion, Interaction and Games, Virtual.","DOI":"10.1145\/3487983.3488305"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Yu, R., Lages, W.S., Nabiyouni, M., Ray, B., Kondur, N., Chandrashekar, V., and Bowman, D.A. (2017, January 18\u201319). Bookshelf and bird: Enabling real walking in large vr spaces through cell-based redirection. Proceedings of the 2017 IEEE Symposium on 3D User Interfaces (3DUI), Los Angeles, CA, USA.","DOI":"10.1109\/3DUI.2017.7893327"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Rockstroh, C., Blum, J., Hardt, V., and G\u00f6ritz, A.S. (2020). Design and evaluation of a virtual restorative walk with room-scale virtual reality and impossible spaces. Front. Virtual Real., 1.","DOI":"10.3389\/frvir.2020.598282"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Marsh, W.E., Putnam, M., Kelly, J.W., Dark, V.J., and Oliver, J.H. (2012, January 4\u20138). The cognitive implications of semi-natural virtual locomotion. Proceedings of the 2012 IEEE Virtual Reality Workshops (VRW), Costa Mesa, CA, USA.","DOI":"10.1109\/VR.2012.6180878"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.cobeha.2017.08.006","article-title":"Event boundaries in memory and cognition","volume":"17","author":"Radvansky","year":"2017","journal-title":"Curr. Opin. Behav. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"28","DOI":"10.37716\/HBAB.2020010105","article-title":"Virtual reality for student learning: Understanding individual differences","volume":"1","author":"Li","year":"2020","journal-title":"Hum. Behav. Brain"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1213","DOI":"10.3758\/s13423-019-01605-w","article-title":"Virtual reality in episodic memory research: A review","volume":"26","author":"Smith","year":"2019","journal-title":"Psychon. Bull. Rev."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1109\/TVCG.2019.2928304","article-title":"Locomotion in place in virtual reality: A comparative evaluation of joystick, teleport, and leaning","volume":"27","author":"Buttussi","year":"2019","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Coomer, N., Bullard, S., Clinton, W., and Williams-Sanders, B. (2018, January 10\u201311). Evaluating the effects of four VR locomotion methods: Joystick, arm-cycling, point-tugging, and teleporting. Proceedings of the 15th ACM Symposium on Applied Perception, Vancouver, BC, Canada.","DOI":"10.1145\/3225153.3225175"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Ribeiro, R.A., Gon\u00e7alves, I., Pi\u00e7arra, M., Seixas Pereira, L., Duarte, C., Rodrigues, A., and Guerreiro, J. (2024, January 11\u201316). Investigating Virtual Reality Locomotion Techniques with Blind People. Proceedings of the CHI Conference on Human Factors in Computing Systems, Honolulu, HI, USA.","DOI":"10.1145\/3613904.3642088"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Usoh, M., Arthur, K., Whitton, M.C., Bastos, R., Steed, A., Slater, M., and Brooks Jr, F.P. (1999, January 8\u201313). Walking walking-in-place flying, in virtual environments. Proceedings of the 26th Annual Conference on Computer Graphics and Interactive Techniques, Los Angeles, CA, USA.","DOI":"10.1145\/311535.311589"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Bhandari, J., Tregillus, S., and Folmer, E. (2017, January 8\u201310). Legomotion: Scalable walking-based virtual locomotion. Proceedings of the 23rd ACM Symposium on Virtual Reality Software and Technology, Gothenburg, Sweden.","DOI":"10.1145\/3139131.3139133"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Van Gemert, T., Chew, S., Kalaitzoglou, Y., and Bergstr\u00f6m, J. (2024, January 11\u201316). Doorways Do Not Always Cause Forgetting: Studying the Effect of Locomotion Technique and Doorway Visualization in Virtual Reality. Proceedings of the CHI Conference on Human Factors in Computing Systems, Honolulu, HI, USA.","DOI":"10.1145\/3613904.3642879"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Hedlund, M. (2024, January 11\u201316). Physical Locomotion for Virtual Environments. Proceedings of the Extended Abstracts of the CHI Conference on Human Factors in Computing Systems, Honolulu, HI, USA.","DOI":"10.1145\/3613905.3638187"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Kontio, R., Laattala, M., Welsch, R., and H\u00e4m\u00e4l\u00e4inen, P. (2023, January 23\u201328). \u201cI Feel My Abs\u201d: Exploring Non-standing VR Locomotion. Proceedings of the ACM on Human-Computer Interaction, Hamburg, Germany.","DOI":"10.1145\/3611069"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Boletsis, C. (2017). The new era of virtual reality locomotion: A systematic literature review of techniques and a proposed typology. Multimodal Technol. Interact., 1.","DOI":"10.3390\/mti1040024"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"7420781","DOI":"10.1155\/2019\/7420781","article-title":"VR locomotion in the new era of virtual reality: An empirical comparison of prevalent techniques","volume":"2019","author":"Boletsis","year":"2019","journal-title":"Adv. Hum. Comput. Interact."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Boletsis, C., and Chasanidou, D. (2022). A typology of virtual reality locomotion techniques. Multimodal Technol. Interact., 6.","DOI":"10.3390\/mti6090072"},{"key":"ref_24","first-page":"2315","article-title":"Virtual locomotion: A survey","volume":"26","author":"MacNeilage","year":"2018","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Sayyad, E., Sra, M., and H\u00f6llerer, T. (2020, January 9\u201313). Walking and teleportation in wide-area virtual reality experiences. Proceedings of the 2020 IEEE International Symposium on Mixed and Augmented Reality (ISMAR), Porto de Galinhas, Brazil.","DOI":"10.1109\/ISMAR50242.2020.00088"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Simeone, A.L., Nilsson, N.C., Zenner, A., Speicher, M., and Daiber, F. (2020, January 22\u201326). The space bender: Supporting natural walking via overt manipulation of the virtual environment. Proceedings of the 2020 IEEE Conference on Virtual Reality and 3D User Interfaces (VR), Atlanta, GA, USA.","DOI":"10.1109\/VR46266.2020.00082"},{"key":"ref_27","unstructured":"Garg, A., Fisher, J.A., Wang, W., and Singh, K.P. (2017, January 6\u201311). ARES: An application of impossible spaces for natural locomotion in VR. Proceedings of the 2017 CHI Conference Extended Abstracts on Human Factors in Computing Systems, Denver, CO, USA."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1109\/TVCG.2009.62","article-title":"Estimation of detection thresholds for redirected walking techniques","volume":"16","author":"Steinicke","year":"2009","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_29","unstructured":"Steinicke, F., Bruder, G., Hinrichs, K., Jerald, J., Frenz, H., and Lappe, M. (2009). Real walking through virtual environments by redirection techniques. Jvrb J. Virtual Real. Broadcast., 6."},{"key":"ref_30","unstructured":"Razzaque, S., Kohn, Z., and Whitton, M.C. (2001, January 3\u20137). Redirected Walking. Proceedings of the Eurographics 2001-Short Presentations, Eurographics Association, Manchester, UK."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1109\/TVCG.2015.2391864","article-title":"Cognitive resource demands of redirected walking","volume":"21","author":"Bruder","year":"2015","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2535","DOI":"10.1109\/TVCG.2021.3067781","article-title":"Arc: Alignment-based redirection controller for redirected walking in complex environments","volume":"27","author":"Williams","year":"2021","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Gerritse, M., Rietzler, M., Van Nimwegen, C., and Frommel, J. (2024, January 11\u201316). The Effect of Spatial Audio on Curvature Gains in VR Redirected Walking. Proceedings of the CHI Conference on Human Factors in Computing Systems, Honolulu, HI, USA.","DOI":"10.1145\/3613904.3641919"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Kohli, L., Burns, E., Miller, D., and Fuchs, H. (2005, January 5\u20138). Combining passive haptics with redirected walking. Proceedings of the 2005 International Conference on Augmented Tele-Existence, Christchurch, New Zealand.","DOI":"10.1145\/1152399.1152451"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Clarence, A., Knibbe, J., Cordeil, M., and Wybrow, M. (2024, January 11\u201316). Stacked Retargeting: Combining Redirected Walking and Hand Redirection to Expand Haptic Retargeting\u2019s Coverage. Proceedings of the CHI Conference on Human Factors in Computing Systems, Honolulu, HI, USA.","DOI":"10.1145\/3613904.3642228"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1109\/MCG.2018.111125628","article-title":"15 years of research on redirected walking in immersive virtual environments","volume":"38","author":"Nilsson","year":"2018","journal-title":"IEEE Comput. Graph. Appl."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1037\/a0018680","article-title":"Age effect on components of episodic memory and feature binding: A virtual reality study","volume":"24","author":"Plancher","year":"2010","journal-title":"Neuropsychology"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2607","DOI":"10.1109\/TVCG.2023.3247063","article-title":"Effects of the visual fidelity of virtual environments on presence, context-dependent forgetting, and source-monitoring error","volume":"29","author":"Mizuho","year":"2023","journal-title":"IEEE Trans. Vis. Comput. Graph."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"983","DOI":"10.1080\/09658211.2021.1953535","article-title":"Immersion, presence, and episodic memory in virtual reality environments","volume":"29","author":"Smith","year":"2021","journal-title":"Memory"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1006\/nimg.2001.0806","article-title":"A temporoparietal and prefrontal network for retrieving the spatial context of lifelike events","volume":"14","author":"Burgess","year":"2001","journal-title":"Neuroimage"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1080\/741943713","article-title":"The specificity of memory enhancement during interaction with a virtual environment","volume":"7","author":"Brooks","year":"1999","journal-title":"Memory"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"895","DOI":"10.1080\/17470218.2012.722657","article-title":"The influence of action on episodic memory: A virtual reality study","volume":"66","author":"Plancher","year":"2013","journal-title":"Q. J. Exp. Psychol."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Daviddi, S., Mastroberardino, S., St Jacques, P.L., Schacter, D.L., and Santangelo, V. (2022). Remembering a virtual museum tour: Viewing time, memory reactivation, and memory distortion. Front. Psychol., 13.","DOI":"10.3389\/fpsyg.2022.869336"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Johanson, C., Gutwin, C., and Mandryk, R.L. (2017, January 15\u201318). The effects of navigation assistance on spatial learning and performance in a 3D game. Proceedings of the Annual Symposium on Computer-Human Interaction in Play, Amsterdam, The Netherlands.","DOI":"10.1145\/3116595.3116602"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Vasylevska, K., and Kaufmann, H. (2017, January 18\u201319). Towards efficient spatial compression in self-overlapping virtual environments. Proceedings of the 2017 IEEE Symposium on 3D User Interfaces (3DUI), Los Angeles, CA, USA.","DOI":"10.1109\/3DUI.2017.7893312"},{"key":"ref_46","unstructured":"Meta (2024, May 02). Meta Quest Tech Specs. Available online: https:\/\/www.meta.com\/quest\/quest-pro\/tech-specs\/."},{"key":"ref_47","unstructured":"Langbehn, E., Eichler, T., Ghose, S., von Luck, K., Bruder, G., and Steinicke, F. (2015, January 10\u201311). Evaluation of an omnidirectional walking-in-place user interface with virtual locomotion speed scaled by forward leaning angle. Proceedings of the GI Workshop on Virtual and Augmented Reality (GI VR\/AR), Sankt Augustin, Germany."},{"key":"ref_48","unstructured":"Thompson, S.E.R., Lange-Nawka, D., and Anderson, C. (2024, May 09). GitHub-Redirected Walking in Impossible Spaces. Available online: https:\/\/github.com\/Flame1190\/CompSci-715-Unity."},{"key":"ref_49","unstructured":"(2023, October 26). Human Benchmark\u2014humanbenchmark.com. Available online: https:\/\/humanbenchmark.com\/tests\/sequence."},{"key":"ref_50","unstructured":"Mailman School of Public Health (2023, April 22). Content Analysis Method and Examples|Columbia Public Health\u2014publichealth.columbia.edu. Available online: https:\/\/www.publichealth.columbia.edu\/research\/population-health-methods\/content-analysis."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Lamers, M.H., and Lanen, M. (2021). Changing between virtual reality and real-world adversely affects memory recall accuracy. Front. Virtual Real., 2.","DOI":"10.3389\/frvir.2021.602087"},{"key":"ref_52","unstructured":"Ahmadi, M., Bai, H., Chatburn, A., W\u00fcnsche, B.C., and Billinghurst, M. (December, January 29). PlayMeBack - Cognitive Load Measurement using Different Physiological Cues in a VR Game. Proceedings of the 28th ACM Symposium on Virtual Reality Software and Technology (VRST \u201922), Tsukuba, Japan."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Ahmadi, M., Bai, H., Chatburn, A., Najatabadi, M.A., W\u00fcnsche, B.C., and Billinghurst, M. (2023, January 25\u201329). Comparison of Physiological Cues for Cognitive Load Measures in VR. Proceedings of the IEEE Conference on Virtual Reality and 3D User Interfaces Abstracts and Workshops (VRW), Shanghai, China.","DOI":"10.1109\/VRW58643.2023.00261"},{"key":"ref_54","doi-asserted-by":"crossref","unstructured":"Ahmadi, M., Michalka, S.W., Lenzoni, S., Najatabadi, M.A., Bai, H., Sumich, A., W\u00fcnsche, B.C., and Billinghurst, M. (2023, January 9\u201311). Cognitive Load Measurement with Physiological Sensors in Virtual Reality during Physical Activity. Proceedings of the 29th ACM Symposium on Virtual Reality Software and Technology (VRST \u201923), Christchurch, New Zealand.","DOI":"10.1145\/3611659.3615704"}],"container-title":["Virtual Worlds"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2813-2084\/4\/3\/39\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T18:35:06Z","timestamp":1760034906000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2813-2084\/4\/3\/39"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,8,29]]},"references-count":54,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,9]]}},"alternative-id":["virtualworlds4030039"],"URL":"https:\/\/doi.org\/10.3390\/virtualworlds4030039","relation":{},"ISSN":["2813-2084"],"issn-type":[{"type":"electronic","value":"2813-2084"}],"subject":[],"published":{"date-parts":[[2025,8,29]]}}}