Complex interactive behaviour involves cognitive, sensation and motor behaviour and may consist of several sub interactive behaviours. It needs to be examined from different points of view. Although explaining everything in one model is not currently possible, it is possible to connect information from different sources to get a better understanding of the interaction to benefit product design. The long-term objective of our study is to develop a methodology for interactive virtual design assessment to study the interactive behaviour and achieve compatibility. This study summarized two experiments which covered many aspects of interactive behaviours in seated posture. Experiment one addressed manipulation behaviour and the hand control design of the car. Experiment two addressed seated reaching behaviour and ATM design. The two experiments are the basis of the advanced study for interactive virtual design assessment. They explored the limitations and advantages of digital prototypes and physical prototypes and suggested that digital prototypes and physical prototypes should be combined to provide design variations and to support human factor testing.