A material and surface selection within the car industry is usually based on a comprehensive study based on sensation and perception, focusing on particular perceived qualities and impressions (emotional functions) through visual and tactile interaction of plastic surfaces. On top of that ‘emotional function’, the ‘technical function’ such as surface roughness or gloss for a certain matter in symbiosis, will result in a number of material and surface proposals. The range of materials fitting into the window of these requirements varies depending on the industry’s ability to hit the target specified in regard to the ‘emotional functions’, usually defined by the designer’s intention. Thus, to be able to get a deeper understanding of how to frame the ‘emotional functions’ and link them to the ‘technical functions’, two user studies were made in this paper. The user studies were made with two different designs however with the same main research target to be able to understand the varieties of these two. The aim of doing so was to be able to find the user study design that was the most time efficient and providing the most significant data linked to the ‘technical functions’ and process control/traceability. However also finding the user study design with the least strains for the participating users in regard to uninterrupted brain activity. By designing the user study in relevant subsets in a certain sequence, user study design nr 2 has proven to be more time efficient and provide more data regarding the soft metrology. Future work will focus on deeper knowledge about how these surfaces different material- and surface properties correlate to the participants responses regarding perceived quality of a car interior design. The development of a new non-contact measurement is also discussed, enabling the possibility to complement and improve the hard metrology set up. © 2020 IOP Publishing Ltd.