## 3 Results  
### Physical Prototyping and Testing in the Field (TIF)  
Control vs. validity: Testing the concept in its correct context without the correct physical materialisation caused some problems regarding external validity. This was especially true for the walk along interface, which was hard to imagine for the participants. Control over the environment was difficult to maintain as well (e.g., the setting was too noisy). Regarding the context, the participants mentioned that it was fun to look at their surroundings and see which real-life environment the final product would be placed in. The main finding reported was that the validity and control could be high if the tested prototype was in its final stage;  
\"I could imagine that I was present in this Pop-up Museum, but the experience still felt like separate tests. It is a little too far removed from the visualization (render).\" (Participant in the field lab test)  
Presence and realism: In terms of immersion, the participants agreed that they could imagine being in the envisioned application. They noted that digital screen-based interfaces were more immersive compared to paper prototypes. The digital screen-based interactions were perceived to be more immersive, more interactive, cheaper and adaptable. The execution of tasks was perceived as realistic. The points of improvement that were suggested were working on the real-life scale of the final product and connecting the separate tests into a more coherent whole. Another proposed point of improvement was increasing the immersion. The question of how realism could be increased in this early stage without high development efforts upfront arises;  
Functionality and interactivity: The interactivity and functionality of the prototypes was sufficient to grasp the general concept of the product. On a cognitive level, the participants reported that they did not have to think a lot when using the paper prototypes and that they were easy to use when somebody gave them instructions. Paper prototyping was well-received as a prototyping method but, unfortunately, it is unresponsive by itself and can be difficult to interpret sometimes. The functionalities of the prototypes were fun to explore since the test was short and the results of the interactions became instantly visible. The participants reported that they liked paper prototyping but preferred digital prototypes. Notwithstanding that paper prototypes can be useful in specific occasions, it remains difficult to compete with the versatility and responsiveness of digital prototypes;  
Note: When rewatching the recorded videos of these tests, very little hesitation was witnessed in the patients during testing in the field. The frictionless experience resulted in some participants smiling when going through the scenario. Usability: The participants found the prototypes easy to use, intuitive and easy to learn, and found it easy to interact with the functionalities of the prototypes. The interviews indicated that the prototypes were moderately fun to test out. The exploration of the prototypes was possible given that there was enough assistance provided by the experimenter. When this condition was met, the contents of the prototypes were informative and experienceable. However, more information was desirable. The participants responded that they would use this way of testing themselves and would not need technical support to perform these types of tests. The envisioned technical support encompassed UX and software engineering. A graphic/VFX designer would be useful as well. The researchers reported that this way of testing made their lives easier and that they would be able to perform testing in this fashion. Regarding effort expectancy, the test was perceived as easy to set up by the participants and their interactions with the system were clear;  
TIF in NPD: In the participants' view, the prototypes added value to the evaluation. They were viewed as innovative and interactive, and allowed for in-depth questioning to see if people understood the prototype.