How do external and internal characteristics of in-vehicle icons affect drivers’ perceived cognitive efficiency? An exploratory study

With the rise of intelligent driving, graphical interactive presentations are gradually replacing traditional physical controls. As essential interactive elements, in-vehicle icons play a critical role in information transmission and user cognition. This study aims to investigate how the external and internal characteristics of in-vehicle icons displayed on the central touchscreen affect drivers’ perceived cognitive efficiency. Based on the Stimulus-Organism-Response (S-O-R) framework, a structural equation model was developed to capture the underlying mechanisms. The partial least squares structural equation modeling (PLS-SEM) method was utilised to analyse 286 valid questionnaires. The results indicate that the internal characteristics of in-vehicle icons (concreteness and familiarity) significantly impact drivers’ cognitive efficiency. In terms of external icon characteristics, colour, shape, and design style significantly influence concreteness and familiarity. The shape of in-vehicle icons directly influences drivers’ cognitive efficiency, whereas colour and design style exert indirect effects by influencing concreteness and familiarity. This study reveals how both internal and external characteristics of icons jointly influence driver cognitive processing efficiency, providing theoretical foundations and practical guidelines for designing icons in in-vehicle human-machine interfaces (HMIs).