Abstract Of late, designers of interactive systems and other exponents of HCI have expressed an increased interest in the contribution which Social Science might make to design. Using recent discussions of "distributed cognition" as our stalking horse, we show that a strategy of simple annexation or incorporation is unlikely to realize the value which the Social Sciences might contribute. Such value will not be derived by a "filling out" of design requirements through the addition of social dimensions to cognitive ones. Rather, it will take the form of a re-appraisal of deep-seated distinctions such as that between the social and the cognitive. In the context of some on-going work at EuroPARC, we examine the possibilities which this re-appraisal might offer. We conclude with a review of the implications of this kind of re-appraisal for the design of interactive systems.