{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T17:02:32Z","timestamp":1791392552248,"version":"4.3.3"},"reference-count":113,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,1,15]],"date-time":"2020-01-15T00:00:00Z","timestamp":1579046400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the Operational Programme Human Capital of the Ministry of European Funds through the Financial Agreement","award":["51675\/09.07.2019, SMIS code 125125"],"award-info":[{"award-number":["51675\/09.07.2019, SMIS code 125125"]}]},{"name":"UEFISCDI proiect 1\/2018 and UPB CRC Research Grant 2017.","award":["1\/2018"],"award-info":[{"award-number":["1\/2018"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this paper, we investigate various machine learning classifiers used in our Virtual Reality (VR) system for treating acrophobia. The system automatically estimates fear level based on multimodal sensory data and a self-reported emotion assessment. There are two modalities of expressing fear ratings: the 2-choice scale, where 0 represents relaxation and 1 stands for fear; and the 4-choice scale, with the following correspondence: 0\u2014relaxation, 1\u2014low fear, 2\u2014medium fear and 3\u2014high fear. A set of features was extracted from the sensory signals using various metrics that quantify brain (electroencephalogram\u2014EEG) and physiological linear and non-linear dynamics (Heart Rate\u2014HR and Galvanic Skin Response\u2014GSR). The novelty consists in the automatic adaptation of exposure scenario according to the subject\u2019s affective state. We acquired data from acrophobic subjects who had undergone an in vivo pre-therapy exposure session, followed by a Virtual Reality therapy and an in vivo evaluation procedure. Various machine and deep learning classifiers were implemented and tested, with and without feature selection, in both a user-dependent and user-independent fashion. The results showed a very high cross-validation accuracy on the training set and good test accuracies, ranging from 42.5% to 89.5%. The most important features of fear level classification were GSR, HR and the values of the EEG in the beta frequency range. For determining the next exposure scenario, a dominant role was played by the target fear level, a parameter computed by taking into account the patient\u2019s estimated fear level.<\/jats:p>","DOI":"10.3390\/s20020496","type":"journal-article","created":{"date-parts":[[2020,1,17]],"date-time":"2020-01-17T04:14:41Z","timestamp":1579234481000},"page":"496","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":78,"title":["An Investigation of Various Machine and Deep Learning Techniques Applied in Automatic Fear Level Detection and Acrophobia Virtual Therapy"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6822-2684","authenticated-orcid":false,"given":"Oana","family":"B\u0103lan","sequence":"first","affiliation":[{"name":"Faculty of Automatic Control and Computers, University POLITEHNICA of Bucharest, Bucharest 060042, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3842-9828","authenticated-orcid":false,"given":"Gabriela","family":"Moise","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Information Technology, Mathematics and Physics, Petroleum-Gas University of Ploiesti, Ploiesti 100680, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1368-7249","authenticated-orcid":false,"given":"Alin","family":"Moldoveanu","sequence":"additional","affiliation":[{"name":"Faculty of Automatic Control and Computers, University POLITEHNICA of Bucharest, Bucharest 060042, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marius","family":"Leordeanu","sequence":"additional","affiliation":[{"name":"Faculty of Automatic Control and Computers, University POLITEHNICA of Bucharest, Bucharest 060042, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8357-5840","authenticated-orcid":false,"given":"Florica","family":"Moldoveanu","sequence":"additional","affiliation":[{"name":"Faculty of Automatic Control and Computers, University POLITEHNICA of Bucharest, Bucharest 060042, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,1,15]]},"reference":[{"key":"ref_1","unstructured":"(2017). Depression and Other Common Mental Disorders: Global Health Estimates, World Health Organization."},{"key":"ref_2","unstructured":"Olesen, J. (2019, October 20). What Is Fear? Types of Phobias and Their Meanings. Available online: https:\/\/www.fearof.net\/what-is-fear-types-of-phobias-and-their-meanings\/."},{"key":"ref_3","unstructured":"Olesen, J. (2019, October 20). Phobia Statistics and Surprising Facts about Our Biggest Fears. Available online: http:\/\/www.fearof.net\/phobia-statistics-and-surprising-facts-about-our-biggest-fears\/."},{"key":"ref_4","unstructured":"(2019, October 20). Uncover the Facts Behind Our Most Common Phobias [Infographic. (2017)]. Available online: https:\/\/blog.nationwide.com\/common-phobias-statistics\/."},{"key":"ref_5","unstructured":"(2019, October 20). Cognitive Behavioral Therapy. Available online: https:\/\/www.psychologytoday.com\/us\/basics\/cognitive-behavioral-therapy."},{"key":"ref_6","unstructured":"Lamson, R.J. (2002). Virtual Reality Immersion Therapy for Treating Psychological, Psychiatric, Medical, Educational and Self-Help Problems."},{"key":"ref_7","unstructured":"Fadden, H. (2019, October 20). Acrophobia (Definition, Causes, Symptoms and Treatment). Available online: https:\/\/www.thehealthyapron.com\/acrophobia-definition-causes-symptoms-treatment.html."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1002\/da.20910","article-title":"Virtual Reality Exposure Therapy in Anxiety Disorders: A Quantitative Meta-Analysis","volume":"29","author":"Opris","year":"2012","journal-title":"Depress. Anxiety"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Picard, R.W. (1997). Affective Computing, MIT Press.","DOI":"10.1037\/e526112012-054"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Calvo, R., D\u2019Mello, S., Gratch, J., and Kappas, A. (2015). Introduction to Affective Computing. The Oxford Handbook of Affective Computing, Oxford University Press.","DOI":"10.1093\/oxfordhb\/9780199942237.013.040"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1052","DOI":"10.1109\/TSMCA.2011.2116000","article-title":"Emotion Assessment from Physiological Signals for Adaptation of Game Difficulty","volume":"41","author":"Chanel","year":"2011","journal-title":"IEEE Trans. Syst. Man Cybern. A Syst. Hum."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"506","DOI":"10.1080\/10447310902963944","article-title":"Dynamic Difficulty Adjustment in Computer Games through Real-Time Anxiety-Based Affective Feedback","volume":"25","author":"Liu","year":"2009","journal-title":"Int. J. Hum.-Comput. Interact."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Calvo, R., D\u2019Mello, S., Gratch, J., and Kappas, A. (2015). Relational Agents in Health Applications: Leveraging Affective Computing to Promote Healing and Wellness. The Oxford Handbook of Affective Computing, Oxford University Press.","DOI":"10.1093\/oxfordhb\/9780199942237.013.010"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Calvo, R., D\u2019Mello, S., Gratch, J., and Kappas, A. (2015). Affective Computing, Emotional Development, and Autism. The Oxford Handbook of Affective Computing, Oxford University Press.","DOI":"10.1093\/oxfordhb\/9780199942237.013.040"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"25","DOI":"10.20870\/IJVR.1995.1.2.2603","article-title":"Effectiveness of Virtual Environment Desensitization in the Treatment of Agoraphobia","volume":"1","author":"North","year":"1995","journal-title":"Int. J. Virtual Real."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1016\/j.janxdis.2009.01.014","article-title":"The use of virtual reality in acrophobia research and treatment","volume":"23","author":"Coelho","year":"2009","journal-title":"J. Anxiety Disord."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"B\u0103lan, O., Moise, G., Petrescu, L., Moldoveanu, A., Leordeanu, M., and Moldoveanu, F. (2019, January 28\u201330). Towards a Human-Centered Approach for VRET Systems\u2014Case study for acrophobia. Proceedings of the 28th International Conference on Information Systems Development, Toulon, France.","DOI":"10.1007\/978-3-030-49644-9_11"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1089\/109493101300210231","article-title":"Redefining Therapeutic Success with Virtual Reality Exposure Therapy","volume":"4","author":"Hoffman","year":"2001","journal-title":"CyberPsychol. Behav."},{"key":"ref_19","unstructured":"(2019, October 20). C2Phobia. Available online: https:\/\/www.c2.care\/en\/c2phobia-treating-phobias-in-virtual-reality\/."},{"key":"ref_20","unstructured":"(2019, October 20). PSIOUS. Available online: https:\/\/www.psious.com\/."},{"key":"ref_21","unstructured":"(2019, October 20). Stim Response Virtual Reality. Available online: https:\/\/www.biopac.com\/application\/virtual-reality\/."},{"key":"ref_22","unstructured":"(2019, October 20). Virtual Reality Medical Center. Available online: https:\/\/vrphobia.com\/."},{"key":"ref_23","unstructured":"(2019, October 20). Virtually Better. Available online: www.virtuallybetter.com."},{"key":"ref_24","unstructured":"(2019, October 20). VR Treatment Program at Duke University School of Medicine. Available online: https:\/\/psychiatry.duke.edu\/virtual-reality-therapy-phobias."},{"key":"ref_25","unstructured":"(2019, October 20). Bravemind. Available online: http:\/\/medvr.ict.usc.edu\/projects\/bravemind\/."},{"key":"ref_26","unstructured":"(2019, October 20). Limbix. Available online: https:\/\/www.limbix.com\/."},{"key":"ref_27","unstructured":"(2019, October 20). Phobos. Available online: https:\/\/samsungvr.com\/view\/Uu9ME9YXR_B."},{"key":"ref_28","unstructured":"(2019, October 20). Activity. Available online: https:\/\/www.unitylab.de\/."},{"key":"ref_29","unstructured":"(2019, October 20). Oculus Rift. Available online: https:\/\/www.oculus.com\/?locale=en_US."},{"key":"ref_30","unstructured":"(2019, October 20). Microsoft Kinect. Available online: https:\/\/developer.microsoft.com\/en-us\/windows\/kinect."},{"key":"ref_31","first-page":"203","article-title":"Contrasting the Effectiveness and Efficiency of Virtual Reality and Real Environments in the Treatment of Acrophobia","volume":"6","author":"Coelho","year":"2008","journal-title":"Psychol. J."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1016\/S0005-7967(01)00023-7","article-title":"Virtual Reality Treatment Versus Exposure in Vivo: A comparative Evaluation in Acrophobia","volume":"40","author":"Emmelkamp","year":"2002","journal-title":"Behav. Res. Ther."},{"key":"ref_33","unstructured":"(2019, October 20). HTC Vive. Available online: https:\/\/www.vive.com\/eu\/."},{"key":"ref_34","unstructured":"(2019, October 20). The Climb. Available online: http:\/\/www.theclimbgame.com\/."},{"key":"ref_35","unstructured":"(2019, October 20). Ritchie\u2019s Plank Experience. Available online: https:\/\/www.viveport.com\/apps\/9347a360-c6ea-4e35-aaf1-9fab4f41cb79\/Richie\u2019s_Plank_Experience\/."},{"key":"ref_36","unstructured":"(2019, October 20). Arachnophobia. Available online: https:\/\/store.steampowered.com\/app\/485270\/Arachnophobia\/."},{"key":"ref_37","unstructured":"(2019, October 20). Limelight. Available online: https:\/\/store.steampowered.com\/app\/544880\/Limelight_VR\/."},{"key":"ref_38","unstructured":"(2019, October 20). Samsung Fearless Cityscapes. Available online: https:\/\/www.oculus.com\/experiences\/gear-vr\/821606624632569\/."},{"key":"ref_39","unstructured":"(2019, October 20). Samsung Fearless Landscapes. Available online: https:\/\/www.oculus.com\/experiences\/gear-vr\/1290835750988761\/."},{"key":"ref_40","unstructured":"(2019, October 20). Samsung Gear V.R. Available online: https:\/\/www.samsung.com\/global\/galaxy\/gear-vr\/."},{"key":"ref_41","unstructured":"(2019, October 20). Samsung Gear S2. Available online: https:\/\/www.samsung.com\/global\/galaxy\/gear-s2\/."},{"key":"ref_42","unstructured":"(2019, October 20). Emotion Definition. Available online: https:\/\/en.oxforddictionaries.com\/definition\/emotion."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1109\/T-AFFC.2011.15","article-title":"DEAP: A Database for Emotion Analysis using Physiological Signals","volume":"3","author":"Koelstra","year":"2012","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_44","unstructured":"Solomon, C.R. (2019, October 20). Emotion. Available online: https:\/\/www.britannica.com\/science\/emotion#ref283140."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1126\/science.164.3875.86","article-title":"Pan-Cultural Elements in Facial Displays of Emotion","volume":"164","author":"Ekman","year":"1969","journal-title":"Science"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"364","DOI":"10.1177\/1754073911410740","article-title":"What is Meant by Calling Emotions Basic","volume":"3","author":"Ekman","year":"2011","journal-title":"Emot. Rev."},{"key":"ref_47","unstructured":"Plutchik, R. (1980). Emotion: Theory, Research, and Experience. Theories of Emotion: 1, New York Academic."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Sacharin, V., Schlegel, K., and Scherer, K.R. (2012). Geneva Emotion Wheel Rating Study (Report), University of Geneva, Swiss Center for Affective Sciences.","DOI":"10.1037\/t36935-000"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1161","DOI":"10.1037\/h0077714","article-title":"A Circumplex Model of Affect","volume":"39","author":"Russell","year":"1980","journal-title":"J. Personal. Soc. Psychol."},{"key":"ref_50","first-page":"3","article-title":"Adaptation in Affective Video Games: A Literature Review","volume":"16","author":"Bontchev","year":"2016","journal-title":"Cybern. Inf. Technol."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"231","DOI":"10.31887\/DCNS.2002.4.3\/tsteimer","article-title":"The Biology of Fear and Anxiety-Related Behaviors","volume":"4","author":"Steimer","year":"2002","journal-title":"Dialogues Clin. Neurosci."},{"key":"ref_52","unstructured":"Golumbic-Zion, E. (2019, October 20). What Is EEG?. Available online: https:\/\/www.mada.org.il\/brain\/articles\/faces-e.pdf."},{"key":"ref_53","unstructured":"Solomon, C.R. (2019, October 20). The Neurobiology of Emotion. Available online: https:\/\/www.britannica.com\/science\/emotion#ref283143."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1080\/02699939308409180","article-title":"Cerebral Asymmetry and Emotion: Conceptual and Methodological Conundrums","volume":"7","author":"Davidson","year":"1993","journal-title":"Cognit. Emot."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1080\/026999398379628","article-title":"Affective Style and Affective Disorders: Perspectives from Affective Neuroscience","volume":"12","author":"Davidson","year":"1998","journal-title":"Cognit. Emot."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"912","DOI":"10.1111\/1469-8986.3860912","article-title":"Voluntary Facial Expression and Hemispheric Asymmetry over the Frontal Cortex","volume":"38","author":"Coan","year":"2001","journal-title":"Psychophysiology"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"106","DOI":"10.1111\/1469-8986.00011","article-title":"Frontal EEG Asymmetry and the Behavioral Activation and Inhibition Systems","volume":"40","author":"Coan","year":"2003","journal-title":"Psychophysiology"},{"key":"ref_58","first-page":"201","article-title":"Emotion Recognition Based on the Asymmetric Left and Right Activation","volume":"3","author":"Park","year":"2011","journal-title":"Int. J. Med. Med Sci."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.ijpsycho.2010.10.002","article-title":"An Integrative Assessment of Brain and Body Function \u2018at rest\u2019 in Panic Disorder: A Combined Quantitative EEG\/Autonomic Function Study","volume":"79","author":"Wise","year":"2011","journal-title":"Int. J. Psychophysiol."},{"key":"ref_60","first-page":"215","article-title":"Auditory Evoked Potentials in Panic Disorder","volume":"16","author":"Knott","year":"1991","journal-title":"J. Psychiatry Neurosci."},{"key":"ref_61","first-page":"34","article-title":"In-Vivo EEG Changes During a Panic Attack in a Patient with Specific Phobia","volume":"3","author":"Engelbregt","year":"2012","journal-title":"J. Med. Cases"},{"key":"ref_62","first-page":"54","article-title":"Clinical and Psychophysiological Study of Patients with Panic Attacks with or without Agoraphobic Disorders","volume":"107","author":"Gordeev","year":"2007","journal-title":"Zh. Nevrol. Psikhiatr. Im. S. S. Korsakova."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1016\/j.ijpsycho.2004.03.001","article-title":"Alpha Oscillations as a Correlate of Trait Anxiety","volume":"53","author":"Knyazev","year":"2004","journal-title":"Int. J. Psychophysiol."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1159\/000026641","article-title":"Appearance of Frontal Midline Theta Activity in Patients with Generalized Anxiety Disorder","volume":"41","author":"Suetsugi","year":"2000","journal-title":"Neuropsychobiology"},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"685","DOI":"10.1016\/j.cogbrainres.2005.04.002","article-title":"A eElectrophysiological Ratio Markers for the Balance between Reward and Punishment","volume":"24","author":"Schutter","year":"2005","journal-title":"Cogntive Brain Res."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/j.biopsycho.2009.10.008","article-title":"EEG Theta\/Beta Ratio in Relation to Fear-Modulated Response-Inhibition, Attentional Control, and Affective Traits","volume":"83","author":"Putman","year":"2010","journal-title":"Biol. Psychol."},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"17507","DOI":"10.3390\/s150717507","article-title":"Evaluation of Fear Using Nonintrusive Measurement of Multimodal Sensors","volume":"15","author":"Choi","year":"2015","journal-title":"Sensors"},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"140","DOI":"10.4172\/2090-4886.1000140","article-title":"Real Time Fear Detection Using Wearable Single Channel Electroencephalogram","volume":"5","author":"Cheemalapati","year":"2016","journal-title":"Sensor Netw. Data Commun."},{"key":"ref_69","doi-asserted-by":"crossref","unstructured":"Petrantonakis, P.G., and Hadjileontiadis, L.J. (2009, January 10\u201312). EEG-based Emotion Recognition Using Hybrid Filtering and Higher Order Crossings. Proceedings of the 2009 3rd International Conference on Affective Computing and Intelligent Interaction and Workshops, Amsterdam, The Netherlands.","DOI":"10.1109\/ACII.2009.5349513"},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1590\/2237-6089-2013-0012","article-title":"Electroencephalographic Findings in Panic Disorder","volume":"35","author":"Carvalho","year":"2013","journal-title":"Trends Psychiatry Psychother."},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1016\/j.ijpsycho.2005.10.024","article-title":"Basic Emotions are Associated with Distinct Patterns of Cardiorespiratory Activity","volume":"61","author":"Rainville","year":"2006","journal-title":"Int. J. Psychophysiol."},{"key":"ref_72","doi-asserted-by":"crossref","unstructured":"Gouizi, K., Reguig, F.B., and Maaoui, C. (2011, January 9\u201311). Analysis Physiological Signals for Emotion Recognition. Proceedings of the 2011 7th International Workshop on Systems, Signal Processing and their Applications (WOSSPA), Tipaza, Algeria.","DOI":"10.1109\/WOSSPA.2011.5931436"},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Muhl, C., and Heylen, D. (2019, January 10\u201312). Cross-Modal Elicitation of Affective Experience. Proceedings of the 2009 3rd International Conference on Affective Computing and Intelligent Interaction and Workshops, Amsterdam, The Netherlands.","DOI":"10.1109\/ACII.2009.5349455"},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1109\/T-AFFC.2011.28","article-title":"ECG Pattern Analysis for Emotion Detection","volume":"3","author":"Agrafioti","year":"2012","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_75","first-page":"729","article-title":"Affect Detection in the Real World: Recording and Processing Physiological Signals","volume":"Volume 1","author":"Healey","year":"2009","journal-title":"Proceedings of the IEEE 3rd International Conference on Affective Computing and Intelligent Interaction"},{"key":"ref_76","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1109\/T-AFFC.2012.2","article-title":"Physiological-based Affect Event Detector for Entertainment Video Applications","volume":"3","author":"Fleureau","year":"2012","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1109\/T-AFFC.2012.4","article-title":"Detecting Naturalistic Expressions of Nonbasic Affect using Physiological Signals","volume":"3","author":"AlZoubi","year":"2010","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_78","doi-asserted-by":"crossref","unstructured":"Westerink, J., Ouwerkerk, M., de Vries, G.-J., de Waele, S., van den Eerenbeemd, J., and van Boven, M. (2009, January 10\u201312). Emotion Measurement Platform for Daily Life Situations. Proceedings of the International Conference (ACII 2009), Amsterdam, The Netherlands.","DOI":"10.1109\/ACII.2009.5349574"},{"key":"ref_79","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1089\/109493102753685908","article-title":"Physiological Monitoring as an Objective Tool in Virtual Reality Therapy","volume":"5","author":"Wiederhold","year":"2002","journal-title":"Cyberpsychol. Behav."},{"key":"ref_80","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1371\/journal.pone.0200306","article-title":"Effects of virtual reality high heights exposure during beam-walking on physiological stress and cognitive loading","volume":"13","author":"Peterson","year":"2018","journal-title":"PLoS ONE"},{"key":"ref_81","doi-asserted-by":"crossref","unstructured":"Kritikos, J., Tzannetos, G., Zoitaki, C., Poulopoulou, S., and Koutsouris, D. (2019, January 20\u201323). Anxiety detection from Electrodermal Activity Sensor with movement & interaction during Virtual Reality Simulation. Proceedings of the 2019 9th International IEEE\/EMBS Conference on Neural Engineering (NER), San Francisco, CA, USA.","DOI":"10.1109\/NER.2019.8717170"},{"key":"ref_82","first-page":"1","article-title":"The Virtual Pole: Exploring Human Responses to Fear of Heights in Immersive Virtual Environments","volume":"6","author":"Lee","year":"2017","journal-title":"J. Virtual Real. Broadcast."},{"key":"ref_83","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.neucom.2013.06.046","article-title":"Emotional State Classification from EEG Data Using Machine Learning Approach","volume":"129","author":"Wang","year":"2014","journal-title":"Neurocomputing"},{"key":"ref_84","unstructured":"Picard, R.W. (2019, October 20). Affective Computing. M.I.T Media Laboratory Perceptual Computing Section Technical Report No. 321. Available online: http:\/\/vismod.media.mit.edu\/tech-reports\/TR-321.pdf."},{"key":"ref_85","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1007\/s10111-003-0143-x","article-title":"Emotion Recognition from Physiological Signals Using Wireless Sensors for Presence Technologies","volume":"6","author":"Nasoz","year":"2004","journal-title":"Cognit. Technol. Work"},{"key":"ref_86","doi-asserted-by":"crossref","first-page":"627892","DOI":"10.1155\/2014\/627892","article-title":"EEG-Based Emotion Recognition Using Deep Learning Network with Principal Component Based Covariate Shift Adaptation. Hindawi Publishing Corporation","volume":"2014","author":"Jirayucharoensak","year":"2014","journal-title":"Sci. World J."},{"key":"ref_87","doi-asserted-by":"crossref","first-page":"813","DOI":"10.1007\/s00146-018-0821-0","article-title":"Can a Machine Think (Anything New)? Automation Beyond Simulation","volume":"34","author":"Fazi","year":"2019","journal-title":"AI Soc."},{"key":"ref_88","doi-asserted-by":"crossref","unstructured":"Jerritta, S., Murugappan, M., Nagarajan, R., and Wan, K. (2011, January 4\u20136). Physiological Signals Based Human Emotion Recognition: A Review. Proceedings of the IEEE 7th International Colloquium on Signal Processing and its Applications, Penang, Malaysia.","DOI":"10.1109\/CSPA.2011.5759912"},{"key":"ref_89","doi-asserted-by":"crossref","first-page":"2067","DOI":"10.1109\/TPAMI.2008.26","article-title":"Emotion Recognition Based on Physiological Changes in Music Listening","volume":"30","author":"Jonghwa","year":"2008","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_90","unstructured":"Wan-Hui, W., Yu-Hui, Q., and Guang-Yuan, L. (April, January 31). Electrocardiography Recording, Feature Extraction and Classification for Emotion Recognition. Proceedings of the WRI World Congress on Computer Science and Information Engineering Los Angeles, Los Angeles, CA, USA."},{"key":"ref_91","first-page":"375","article-title":"Multimodal Emotion Recognition from Expressive Faces, Body Gestures and Speech","volume":"Volume 247","author":"Boukis","year":"2007","journal-title":"Artificial Intelligence and Innovations 2007: From Theory to Applications"},{"key":"ref_92","doi-asserted-by":"crossref","unstructured":"Ng, H.W., Nguyen, V.D., Vonikakis, V., and Winkler, S. (2015, January 9\u201313). Deep Learning for Emotion Recognition on Small Datasets using Transfer Learning. Proceedings of the 2015 ACM on International Conference on Multimodal Interaction (ICMI \u201915), New York, NY, USA.","DOI":"10.1145\/2818346.2830593"},{"key":"ref_93","doi-asserted-by":"crossref","unstructured":"Teo, J., Chew, L.H., Chia, J.T., and Mountstephens, J. (2018). Classification of Affective States via EEG and Deep Learning. Int. J. Adv. Comput. Sci. Appl., 9.","DOI":"10.14569\/IJACSA.2018.090517"},{"key":"ref_94","unstructured":"Liu, C., Rani, P., and Sarkar, N. (2005, January 2\u20136). An Empirical Study of Machine Learning Techniques for Affect Recognition in Human-Robot Interaction. Proceedings of the IEEE\/RSJ International Conference on Intelligent Robots and Systems, Edmonton, AB, Canada."},{"key":"ref_95","doi-asserted-by":"crossref","unstructured":"B\u0103lan, O., Moise, G., Petrescu, L., Moldoveanu, A., Leordeanu, M., and Moldoveanu, F. (2020). Emotion Classification Based on Biophysical Signals and Machine Learning Techniques. Symmetry, 12.","DOI":"10.3390\/sym12010021"},{"key":"ref_96","unstructured":"Ray, L.C., and Fukuoka, Y. (2019, January 23\u201325). Machine Learning and Therapeutic Strategies in VR. Proceedings of the 9th International Conference on Digital and Interactive Arts (Artech 2019), Braga, Portugal."},{"key":"ref_97","doi-asserted-by":"crossref","unstructured":"Hu, F., Wang, H., Chen, J., and Gong, J. (2018, January 24\u201327). Research on the characteristics of acrophobia in virtual altitude environment. Proceedings of the 2018 IEEE International Conference on Intelligence and Safety for Robotics, Shenyang, China.","DOI":"10.1109\/IISR.2018.8535774"},{"key":"ref_98","doi-asserted-by":"crossref","unstructured":"\u0160alkevicius, J., Dama\u0161evi\u010dius, R., Maskeliunas, R., and Laukien\u0117, I. (2019). Anxiety Level Recognition for Virtual Reality Therapy System Using Physiological Signals. Electronics, 8.","DOI":"10.3390\/electronics8091039"},{"key":"ref_99","unstructured":"B\u0103lan, O., Moise, G., Moldoveanu, A., Leordeanu, M., and Moldoveanu, F. (2019, January 8\u201314). Automatic Adaptation of Exposure Intensity in VR Acrophobia Therapy, Based on Deep Neural Networks. Proceedings of the Twenty-Seventh European Conference on Information Systems (ECIS2019), Stockholm-Uppsala, Sweden."},{"key":"ref_100","unstructured":"B\u0103lan, O., Moise, G., Moldoveanu, A., Moldoveanu, F., and Leordeanu, M. (December, January 28). Does Automatic Game Difficulty Level Adjustment Improve Acrophobia Therapy? Differences from Baseline. Proceedings of the VRST \u201918, Tokyo, Japan."},{"key":"ref_101","doi-asserted-by":"crossref","first-page":"211","DOI":"10.3389\/fneur.2017.00211","article-title":"A New Questionnaire for Estimating the Severity of Visual Height Intolerance and Acrophobia by a Metric Interval Scale","volume":"8","author":"Huppert","year":"2017","journal-title":"Front. Neurol."},{"key":"ref_102","unstructured":"(2019, October 20). Acticap Xpress Bundle. Available online: https:\/\/www.brainproducts.com\/productdetails.php?id=66."},{"key":"ref_103","unstructured":"(2019, October 20). Shimmers Multisensory. Available online: http:\/\/www.shimmersensing.com\/."},{"key":"ref_104","unstructured":"(2019, October 20). Shimmer3 GSR+ Unit. Available online: https:\/\/www.shimmersensing.com\/products\/shimmer3-wireless-gsr-sensor."},{"key":"ref_105","unstructured":"(2018, November 20). Scikit Learn Python Library. Available online: http:\/\/scikit-learn.org."},{"key":"ref_106","unstructured":"(2019, October 20). Tensor Flow Python Framework. Available online: https:\/\/www.tensorflow.org\/."},{"key":"ref_107","unstructured":"(2019, October 20). Keras Library. Available online: https:\/\/keras.io\/."},{"key":"ref_108","unstructured":"(2019, October 20). Unity Game Engine. Available online: https:\/\/unity.com\/."},{"key":"ref_109","unstructured":"(2019, October 20). Open Vibe. Available online: http:\/\/openvibe.inria.fr\/."},{"key":"ref_110","unstructured":"(2019, October 20). Lab Stream Layer. Available online: https:\/\/github.com\/sccn\/labstreaminglayer."},{"key":"ref_111","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1177\/155005940603700313","article-title":"EEG Correlates of Startle Reflex with Reactivity to Eye Opening in Psychiatric Disorders: Preliminary Results","volume":"37","author":"Arikan","year":"2006","journal-title":"Clin. EEG Neurosci."},{"key":"ref_112","first-page":"1","article-title":"The Effects Virtual Reality Has on Physiological Responses as Compared to Two-Dimensional Video","volume":"1","author":"Kometer","year":"2010","journal-title":"J. Adv. Stud. Sci."},{"key":"ref_113","first-page":"1672","article-title":"Using Noninvasive Wearable Computers to Recognize Human Emotions from Physiological Signals","volume":"11","author":"Lisetti","year":"2004","journal-title":"J. Appl. Signal Process."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/2\/496\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T14:26:30Z","timestamp":1760365590000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/2\/496"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,1,15]]},"references-count":113,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2020,1]]}},"alternative-id":["s20020496"],"URL":"https:\/\/doi.org\/10.3390\/s20020496","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,1,15]]}}}