Human factors is one of the critical issues in Information Technology, as industry realizes the need to change from technology-oriented goals to meet the demands of computer users. Human factors can help to improve Informatics Usability for real people, and to reduce the huge people-costs of human machine interactions. This book has been developed from lectures given at an Advanced Study course, sponsored by the European Science and Technology Research Committee of the Commission of the European Communities (CREST), and by the Science and Engineering Research Council (SERC) of the UK. It has three objectives: 1. To review the knowledge and methods available from the field of human factors for improving the usability of informatics systems; 2. To describe recent theoretical and methodological developments in the area; 3. To stimulate increased application of this expertise.