We suggest that HCI designs characteristically embody multiple, distinct psychological claims, that virtually every aspect of a system's usability is overdetermined by independent psychological rationales inherent in its design. These myriad claims cohere in being implemented together in a running system. Thus, ItCI artifacts themselves are perhaps the most effective medium for theory development in ItCI. We advance a framework for articulating the psychological claims embodied by artifacts. This proposal reconciles the contrasting perspectives of theory-based design and hermeneutics, and clarifies the apparent paradox of ItCI application leading HCI theory.KEYWORDS: theory, design, task analysis As a field of inquiry, the study of human-computer interaction is perplexing. In the midst of enormous activity and considerable technical progress, very fundamental issues remain unresolved. For example, it would seem to be axiomatic that scientific psychology has much to contribute to an understanding of IlC1 phenomena and to the design of IICI artifacts. ttowever, the role of scientific psychology in IICI is in dispute.Some theorists argue that only certain fairly narrow conceptions of psychology can successfully be applied. Newell and Card [14] warn that psychology might be driven out of IICI unless it can provide quantitatively predictive cognitive models. This approach focuses of necessity on relatively low-level asPermission to copy without fee all or part of this material Is gl'anted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and Its date appear, and notice Is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. Other theorists hold that pursuing the goal of developing cognitive science theories of HCI may impair progress toward usefully understanding IICI phenomena and effectively contributing to design [20]. This approach stresses the distortion and oversimplification inherent in laboratory-bound psychology and in conventional views of theory-based design. In contrast, this hermeneutic approach recommends treating situations, users and artifacts as unique instances. Understanding such instances is seen as an interactive process of consensual interpretation: the goal is not to identify a theory-base for application to design, but to design through a subjective process of discovery [21].Both approaches are problematic [3,5]. The limited scope of quantitative theories precludes adequate grounding for design decisions. Such theory-based design has never occurred on a nontrivial scale. On the other hand, bridges from hermeneutic interpretation into design decision-making are essentially mystical. There is no systematic methodology, no conceptual framework, no explicit way to abstract from particular experiences.Indeed, interface innovations frequently lead I ICI research rather than following from it in ...