What happens when humans produce new technologies?Two interdependent perspectives from which such a production can be approached are adopted: & bull; How and why constructs that have their origins in human mental life are embodied in physical environments when people fabricate their habitat, even to the point of those constructs becoming that very habitat & bull; How and why these fabricated habitats affect, and feed back into, human mental life. The aim of the CT research programme is to determine, in general, which technologies, and in particular, which interactive computer-based technologies, are