ABSTRACT This paper argues from extensive research findings in design psychology and industrial design processes, as well as our own observations, that interactive generative systems can be powerful tools for human designers. Moreover, interactive generative systems can fit naturally into human design thinking and industrial design practice. This discussion is focused on aesthetic design fields like knitwear and graphic design, but is largely applicable to major branches of engineering. Human designers and generative systems have complementary abilities. Humans are extremely good at perceptual evaluation of designs, according to criteria that are extremely hard to program. As a result, they can provide fitness evaluations for evolutionary generative systems. They can also tailor the biases on generation systems use to reach useful solutions quickly. We discuss an application of these approaches: Kelly's evolutionary systems for color scheme design. Automatic design systems can work interactively with human designers by generating complete designs from partial specifications, that can they be used as starting points for designing by modification. We discuss an application of this approach: Eckert's garment shape design system. KEYWORDS Generative Systems, Automatic Design, Design Psychology, Aesthetic Design, Conceptual Design 1 INTRODUCTION - ACHIEVING HUMAN-COMPUTER SYNERGY The purpose of intelligent systems for supporting human designers is to achieve human-computer synergy, to achieve greater creativity and effectiveness than either humans or artificial intelligence (AI) systems can manage on their own. This entails embedding intelligent systems into human design activities, not only to take over subtasks that humans find difficult or tedious, but also to exploit the power of human design thinking. The argument of this paper is that generative systems for automatic design can be powerful tools for human designers, but need to be grounded in an understanding of design. While the intrinsic structure of the design problem is the most profound influence on what designers do, their strategies and actions are powerfully constrained by their cognitive capacities, and by the representations and operations afforded by the tools they use. Effective tools must be engineered to fit (1) the task, (2) the cognitive characteristics of their users, (3) their users' skills, and (4) the organization of the design process within its industrial context. This requires both an awareness of design psychology and a thorough study of the design processes in which a tool will be used. Effective interactive AI systems should enable human designers to exploit the strengths of AI systems, to perform complex computations, handle multiple constraints and explore alternative solutions. As interactive tools, generative systems can exploit the strengths of human designers, to evaluate the characteristics and qualities of designs perceptually, and to use visual stimuli as triggers to imagine novel designs. Automatic design systems can work interactively in different roles (which can be combined): evolving designs iteratively with humans performing selection and fitness evaluation; completing designs from partial specifications; and generating initial candidate designs for humans to modify. 1.1 The Power of Bias For most interesting classes of artifacts, the space of possible designs is immense. At any stage in the construction of a design, the vast majority of possible changes are either nonsensical or foolish. So to create a design that meets its designers' objectives, the generation process must be strongly directed. In the generation of successive partial designs, this direction can come from the expressive power of the representation in which the design is expressed, from the range of design creation actions available, and from the ways in which these actions are selected. In the evaluation of successive partial designs, it can come from the constraints the design must meet and the qualities it must have. Human designers combine all these sources of guidance. Automatic design systems need very strong direction to produce appropriate rather than inappropriate artifacts: they need to be biased towards producing some designs rather than others. But when their users want to explore alternative designs for reasons that cannot easily be programmed, bias is harmful: automatic design systems should cover the whole space of appropriate designs, and not just a small subset of it. In this paper, we argue that stand-alone generative systems have biases that are far too strong for many applications. A more fruitful approach is to build in constant domain constraints (for instance in tailoring, that the sleeve crown curve is the same length as the armhole curve), and allow users either to program constraints and biases, or to provide the biasing themselves interactively. 1.2 Generative Systems for Visuospatial Conceptual Design In this pa