@phdthesis{Stauffert2022,
  author    = {Stauffert, Jan-Philipp},
  title     = {Temporal Confounding Effects in Virtual and Extended Reality Systems},
  doi       = {10.25972/OPUS-29060},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-290609},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Latency is an inherent problem of computing systems. Each computation takes time until the result is available. Virtual reality systems use elaborated computer resources to create virtual experiences. The latency of those systems is often ignored or assumed as small enough to provide a good experience. This cumulative thesis is comprised of published peer reviewed research papers exploring the behaviour and effects of latency. Contrary to the common description of time invariant latency, latency is shown to fluctuate. Few other researchers have looked into this time variant behaviour. This thesis explores time variant latency with a focus on randomly occurring latency spikes. Latency spikes are observed both for small algorithms and as end to end latency in complete virtual reality systems. Most latency measurements gather close to the mean latency with potentially multiple smaller clusters of larger latency values and rare extreme outliers. The latency behaviour differs for different implementations of an algorithm. Operating system schedulers and programming language environments such as garbage collectors contribute to the overall latency behaviour. The thesis demonstrates these influences on the example of different implementations of message passing. The plethora of latency sources result in an unpredictable latency behaviour. Measuring and reporting it in scientific experiments is important. This thesis describes established approaches to measuring latency and proposes an enhanced setup to gather detailed information. The thesis proposes to dissect the measured data with a stacked z-outlier-test to separate the clusters of latency measurements for better reporting. Latency in virtual reality applications can degrade the experience in multiple ways. The thesis focuses on cybersickness as a major detrimental effect. An approach to simulate time variant latency is proposed to make latency available as an independent variable in experiments to understand latency's effects. An experiment with modified latency shows that latency spikes can contribute to cybersickness. A review of related research shows that different time invariant latency behaviour also contributes to cybersickness.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Madeira2022,
  author    = {Madeira, Octavia},
  title     = {The Human-Experimental Virtual Elevated Plus-Maze as an Anxiety Model},
  doi       = {10.25972/OPUS-28147},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-281478},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Anxiety research is one of the major psychological research domains and looks back on decades of research activity. Traditionally, novel theories and approaches are tested utilizing animal models. One way to study inherent anxiety in rodents is the elevated plus-maze (EPM). The EPM is a plus-shaped platform with two closed, i.e., walled, arms and two open unwalled arms. If given the opportunity to freely explore the apparatus, rodents instinctively avoid the open arms to protect themselves from predators. Hence, they spent less time on open and more time on closed arms, which is behaviorally associated with general anxiety. In the course of the pharmacological validation, it was found that this exploratory pattern can be reversed by anxiolytic substances, e.g., benzodiazepines, or potentiated by anxiogenics. One of the significant advantages of the EPM is that no prior training session is required in contrast to conditioning studies, thus allowing to observe natural behavior. Therefore, together with the economic and uncomplicated setup, the EPM has become a standard preclinical rodent anxiety test over the decades. In order to validate these rodent anxiety tests, there have recently been attempts to retranslate them to humans. A paramount of cross-species validation is not only the simple transferability of these animal tests but also the observation of anxiety behaviors that are evolutionarily conserved across species. Accordingly, it could be possible to conclude various factors associated with the etiology and maintenance of anxiety disorders in humans. So far, convincing translations of the EPM to humans are still lacking. For that reason, the primary aim of this dissertation is to retranslate the EPM throughout three studies and to evaluate cross-species validity critically. Secondly, the undertaken studies are set out to observe ambulatory activity equivalent to rodent EPM behavior, i.e., open arm avoidance. Thirdly, the undertaken studies aimed to assess the extent to which trait anxiety influences human exploratory activity on the platform to associate it with the assumption that rodent EPM-behavior is a reflection of general anxiety. Finally, virtual reality (VR) was the method of choice to maintain the economic advantage and adjust the EPM size to humans. Study 1 (N = 30) was set up to directly transfer the rodent EPM regarding test design and experimental procedure using a Computer Automatic Virtual Environment (CAVE). The results revealed that humans unlike rodents display a general open arms approach during free exploration. However, open arm avoidance was associated with high trait anxiety and acrophobia (fear of height), which was initially assessed as a control variable due to the virtual platform height. Regression analyses and subjective anxiety ratings hinted at a more significant influence of acrophobia on open arm avoidance. In addition, it was assumed that the open arms approach might have resulted from claustrophobic tendencies experienced in the closed arms due to the high walls. Study 2 (N = 61) sought to differentiate the influence of trait anxiety and acrophobia and adapt the virtual EPM to humans. Therefore, parts of the platform held a semi-transparent grid-floor texture, and the wall height on the closed arms was reduced to standard handrail level. Moreover, participants were priorly screened to exclude clinically significant levels of acrophobia, claustrophobia, and agoraphobia. The data on general exploratory activity showed no arm preference. Regression analyses confirmed that acrophobia is related to open arm avoidance, corroborating the finding of Study 1. Surprisingly, for trait anxiety, the result of Study 1 could not be replicated. Instead, for trait anxiety, no significant effect was found indicating that predominantly fear of heights shapes human EPM behavior even on a subclinical stage. In Study 3 (N = 57), the EPM was embedded into a city setting to 1) create a more natural human environment and 2) eliminate height. Furthermore, a head-mounted display was utilized for VR presentation, and arousal ratings were introduced. Participants were screened for high and low levels of trait anxiety and agoraphobia, and claustrophobia. Replicating the findings of Study 2, no difference in open and closed arm activity was observed, and no effect was found in relationship with trait anxiety. The data on anxiety ratings and claustrophobia suggest a positive correlation indicating that in this city EPM, claustrophobic tendencies might play a role in closed arm avoidance. In summary, this thesis added valuable insights into the retranslation of a well-established standard anxiety test used in rodents. However, it also majorly challenges current findings on the cross-species validity of the EPM. Various explanatory models for the results are critically discussed and associated with clinical implications concerning future research.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Winter2022,
  author    = {Winter, Carla},
  title     = {Evaluation der Verwendung von Virtueller Realit{\"a}t (VR) als Erg{\"a}nzung zum Laufbandtraining im Rahmen der Behandlung von Gangst{\"o}rungen bei Patienten mit Multipler Sklerose (MS) und Schlaganfall},
  doi       = {10.25972/OPUS-28054},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-280544},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Die Rehabilitation von Gangst{\"o}rungen bei Patienten mit MS und Schlaganfall erfolgt h{\"a}ufig mithilfe eines konventionellen Laufbandtrainings. Einige Studien haben bereits gezeigt, dass durch eine Erweiterung dieses Trainings um eine virtuelle Realit{\"a}t die Motivation der Patienten gesteigert und die Therapieergebnisse verbessert werden k{\"o}nnen. In der vorliegenden Studie wurde eine immersive VR-Anwendung (unter Verwendung eines HMD) f{\"u}r die Gangrehabilitation von Patienten evaluiert. Hierbei wurden ihre Anwendbarkeit und Akzeptanz gepr{\"u}ft sowie ihre Kurzzeiteffekte mit einer semi-immersiven Pr{\"a}sentation (unter Verwendung eines Monitors) und mit einem konventionellen Laufbandtraining ohne VR verglichen. Der Fokus lag insbesondere auf der Untersuchung der Anwendbarkeit beider Systeme und der Auswirkungen auf die Laufgeschwindigkeit und Motivation der Benutzer. Im Rahmen einer Studie mit Innersubjekt-Design nahmen zun{\"a}chst 36 gesunde Teilnehmer und anschließend 14 Patienten mit MS oder Schlaganfall an drei experimentellen Bedingungen (VR {\"u}ber HMD, VR {\"u}ber Monitor, Laufbandtraining ohne VR) teil. Sowohl in der Studie mit gesunden Teilnehmern als auch in der Patientenstudie zeigte sich in der HMD-Bedingung eine h{\"o}here Laufgeschwindigkeit als beim Laufbandtraining ohne VR und in der Monitor-Bedingung. Die gesunden Studienteilnehmer berichteten {\"u}ber eine h{\"o}here Motivation nach der HMD-Bedingung als nach den anderen Bedingungen. Es traten in beiden Gruppen keine Nebenwirkungen im Sinne einer Simulator Sickness auf und es wurden auch keine Erh{\"o}hungen der Herzfrequenzen nach den VR-Bedingungen detektiert. Die Bewertungen des Pr{\"a}senzerlebens waren in beiden Gruppen in der HMD-Bedingung h{\"o}her als in der Monitor-Bedingung. Beide VR-Bedingungen erhielten hohe Bewertungen f{\"u}r die Benutzerfreundlichkeit. Die meisten der gesunden Teilnehmer (89 \%) und Patienten (71 \%) pr{\"a}ferierten das HMD-basierte Laufbandtraining unter den drei Trainingsformen und die meisten Patienten k{\"o}nnten sich vorstellen, es h{\"a}ufiger zu nutzen. Mit der vorliegenden Studie wurde eine strukturierte Evaluation der Anwendbarkeit eines immersiven VR-Systems f{\"u}r die Gangrehabilitation gepr{\"u}ft und dieses erstmals in den direkten Vergleich zu einem semi-immersiven System und einem konventionellen Training ohne VR gesetzt. Die Studie best{\"a}tigte die Praktikabilit{\"a}t der Kombination eines Laufbandtrainings mit immersiver VR. Aufgrund ihrer hohen Benutzerfreundlichkeit und der geringen Nebenwirkungen scheint diese Trainingsform besonders f{\"u}r Patienten geeignet zu sein, um deren Trainingsmotivation und Trainingserfolge, wie z. B. die Laufgeschwindigkeit, zu steigern. Da immersive VR-Systeme allerdings nach wie vor spezifische technische Installationsprozeduren erfordern, sollte f{\"u}r die spezifische klinische Anwendung eine Kosten-Nutzen-Bewertung erfolgen.},
  subject      = {Multiple Sklerose},
  language  = {de}
}
@phdthesis{Grossekathoefer2022,
  author    = {Großekath{\"o}fer, Jonas David},
  title     = {Virtually Valid? On the Importance of Ecological Validity and Virtual Reality for Social Attention Research},
  doi       = {10.25972/OPUS-26041},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260417},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Gazes are of central relevance for people. They are crucial for navigating the world and communicating with others. Nevertheless, research in recent years shows that many findings from experimental research on gaze behavior cannot be transferred from the laboratory to everyday behavior. For example, the frequency with which conspecifics are looked at is considerably higher in experimental contexts than what can be observed in daily behavior. In short: findings from laboratories cannot be generalized into general statements. This thesis is dedicated to this matter. The dissertation describes and documents the current state of research on social attention through a literature review, including a meta-analysis on the /gaze cueing/ paradigm and an empirical study on the robustness of gaze following behavior. In addition, virtual reality was used in one of the first studies in this research field. Virtual reality has the potential to significantly improve the transferability of experimental laboratory studies to everyday behavior. This is because the technology enables a high degree of experimental control in naturalistic research designs. As such, it has the potential to transform empirical research in the same way that the introduction of computers to psychological research did some 50 years ago. The general literature review on social attention is extended to the classic /gaze cueing/ paradigm through a systematic review of publications and a meta-analytic evaluation (Study 1). The cumulative evidence supported the findings of primary studies: Covert spatial attention is directed by faces. However, the experimental factors included do not explain the surprisingly large variance in the published results. Thus, there seem to be further, not well-understood variables influencing these social processes. Moreover, classic /gaze cueing/ studies have limited ecological validity. This is discussed as a central reason for the lack of generalisability. Ecological validity describes the correspondence between experimental factors and realistic situations. A stimulus or an experimental design can have high and low ecological validity on different dimensions and have different influences on behavior. Empirical research on gaze following behavior showed that the /gaze cueing/ effect also occurs with contextually embedded stimuli (Study 2). The contextual integration of the directional cue contrasted classical /gaze cueing/ studies, which usually show heads in isolation. The research results can thus be transferred /within/ laboratory studies to higher ecologically valid research paradigms. However, research shows that the lack of ecological validity in experimental designs significantly limits the transferability of experimental findings to complex situations /outside/ the laboratory. This seems to be particularly the case when social interactions and norms are investigated. However, ecological validity is also often limited in these studies for other factors, such as contextual embedding /of participants/, free exploration behavior (and, thus, attentional control), or multimodality. In a first study, such high ecological validity was achieved for these factors with virtual reality, which could not be achieved in the laboratory so far (Study 3). Notably, the observed fixation patterns showed differences even under /most similar/ conditions in the laboratory and natural environments. Interestingly, these were similar to findings also derived from comparisons of eye movement in the laboratory and field investigations. These findings, which previously came from hardly comparable groups, were thus confirmed by the present Study 3 (which did not have this limitation). Overall, /virtual reality/ is a new technical approach to contemporary social attention research that pushes the boundaries of previous experimental research. The traditional trade-off between ecological validity and experimental control thus becomes obsolete, and laboratory studies can closely inherit an excellent approximation of reality. Finally, the present work describes and discusses the possibilities of this technology and its practical implementation. Within this context, the extent to which this development can still guarantee a constructive classification of different laboratory tests in the future is examined.},
  subject      = {Aufmerksamkeit},
  language  = {en}
}