Human-computer interaction (HCI) study is the region of intersection between psychology and the social sciences, on the one hand, and computer science and technology, on the other. HCI researchers analyze and design specific user interface technologies (e.g. pointing devices). They study and improve the processes of technology development (e.g. task analysis, design rationale). They develop and evaluate new applications of technology (e.g. word processors, digital libraries). Throughout the past two decades, HCI has progressively integrated its scientific concerns with the engineering goal of improving the usability of computer systems and applications, which has resulted in a body of technical knowledge and methodology. HCI continues to provide a challenging test domain for applying and developing psychological and social theory in the context of technology development and use.