This paper presents two types of cognitive experiments and one developing system for realization of the mutual adaptive interface (MADI). Effectiveness of Verbal Protocol and Operational Sequence History for the cognitive behavior analysis has been evaluated from the experimental data obtained by first type of cognitive experiments using nuclear power plant simulator. Effectiveness of our proposed systematic analysis method to trace subjects’ cognitive processes has been evaluated from the second type of experiments similar to the first one but using a voice recognition device. Based on the both results, a future development plan of the real-time cognitive process estimation system is discussed in relation to MADI.