To evaluate the effects of human cognitive characteristics on situation awareness, a computational situation assessment model of nuclear power plant operators has been developed, as well as a procedure to apply the developed model to the design of human system interfaces (HSIs). The concept of the proposed procedure is to identify the key information source, which is expected to guarantee fast and accurate diagnosis when operators attend to it. The developed computational model is used to search the diagnostic paths and the key information source. In this study, an experiment with twelve trained participants was executed to validate the effectiveness of the proposed procedure. Eighteen scenarios covering various accidents were administered twice for each subject, and experimental data were collected and analyzed. As a result of the data analysis, it was validated that the salience level of information sources significantly influences the attention of operators, and the first observation of the key information sources leads operators to a quick and correct situation assessment. Therefore, we conclude that the proposed procedure for applying the developed model to HSI design is effective. (C) 2013 Elsevier Ltd. All rights reserved.