The overall objective is to develop new techniques for the creation of Mixed Reality (MR) applications that use the Passthrough of Virtual Reality (VR) headsets and expressive avatars in multi-user applications, taking advantage of recent technological advances in headsets. These applications will be validated as use cases through the development of applications for the assessment of spatial memory and its orientation strategies, as well as for social stress tasks. Synthesizing the specific objectives outlined in the research proposal, they would be as follows:

1. Identify the real limitations and advantages of the selected headsets;
2. Define generic and specific design guides for perspective-taking tasks and spatial orientation strategies; as well as for implementing realistic avatars for social stress tasks;
3. Using these guides, as use cases, design and develop applications for the assessment of spatial memory controlling perspective-taking ability, allocentric and egocentric spatial orientation strategies, and a multi-user application to induce acute psychosocial stress by modulating avatar reliability;
4. Validate the applications regarding their usability and sense of presence, as well as comprehensively evaluate them from a psychological perspective to determine their contribution in the field of health, particularly in psychology.

From a computer science perspective, developing new techniques for creating MR applications that use the Passthrough of VR headsets and the inclusion of realistic avatars in multi-user applications, as well as defining generic design guides, will enable these advances to be applied in different fields. For instance, they could be used in interior design or multi-user therapy applications to address social phobia.

From a psychological point of view, this project is of special interest for the following reasons:

• No study has developed tasks in MR to determine the sense of orientation and perspective-taking by isolating variables, along with pure spatial orientation strategies, both with and without memory load;
• No multi-user application has been created to implement a psychosocial stressor with different levels of reliability and observe its psychophysiological and cognitive effects in a VR environment. This could be valuable for researching the effects of acute stress and could have a great impact on its treatment and rehabilitation.

Through this project, the assessment of spatial memory and its orientation strategies will be significantly improved, and an effective and easily applicable tool will be available for evaluating the effects of psychosocial stressors in research. For all these reasons, our proposal is groundbreaking and will establish us as a leading group in Extended Reality (XR) for spatial memory and social stress. It is worth noting that reports on the future of XR in the healthcare industry predict a significant social and economic impact in the coming years, and this project will contribute to this achievement.

Finally, we would like to highlight the interest expressed by 6 EPOs from across Spain in the project. Among them, 4 are software development and commercialization companies, demonstrating an interest in the IT contribution of the project, and 2 are associations interested in the applicability of its results.