In this paper, we examine, from a cognitive standpoint, the issue of collective decision-making in participatory design groups. These multi-occupational group (manufacturing operators, foremen, maintenance mechanics, the method agent, the shop foreman, draftsmen, etc.) are asked to redesign the equipment of a production line in a factory manufacturing steel tubes. Our analysis is focused on the cognitive side of the redesign activity, and especially on the coUective evaluation processes. From the transcripts of the meetings, we have examined how the co-designers come to an agreement about the redesigned equipment. We show that the criteria sponteneously used for the evaluation of the solutions are far wider (quantitatively and qualitatively) than the list of functional criteria prescribed to the co-designers for the decision-making process. This study has led to the development of an evaluation method, named CRITERIA, which is briefly described.
