With respect to the design of visual information display (VID) for process control, this study experimentally evaluated the effectiveness of functionally abstracted information in the task of fault diagnosis. The benefits of functional properties of work domain have been emphasized by ecological interface design (EID), a relatively new design framework for human-machine interfaces. According to the concept of EID, multilevel information representation based on abstraction hierarchy of work domain is expected to be advantageous for supporting the operator's problem solving. To investigate the advantage of EID application, an experiment was conducted using a computer-based simulation of the secondary cooling system of nuclear power plants. Three interfaces were compared: the first representing only the physical properties of the process, the second representing purpose-related generalized functions (GFs) in addition to the physical properties, and the third representing abstract functions (AFs) governing the GFs in addition to the physical properties. The results showed that the diagnostic performance was improved by displaying functionally abstracted information at both levels, and that the usefulness of the abstract information was dependent on the complexity of the diagnosis problems. (C) 2001 Elsevier Science Ltd. All rights reserved.