This paper explores differences and similarities between novice and expert users of interactive artifacts. In order to achieve this, protocol analysis was used to identify users’ cognitive categories, knowledge categories and knowledge representation. This research is based on the premises that knowledge — domain-specific knowledge in particular — plays a significant role in distinguishing a novice from an expert user, and the way in which they use technologically interactive devices. The differences between expert and novice users were compared and identified with associated knowledge and knowledge representation for each cognitive category. These constitute the features that differentiate them as they reflect the kind of processes, representations, strategies or knowledge organisation that may occur for each cognitive category during the interaction. The paper also addresses the transitional process through which a novice becomes an expert and concludes about this finding’s implication to design.