Some concepts, such as colour concepts or value concepts, seem to bear traces of the mind's own make-up. For instance, an extreme position would be that colours and values are not in the world at all, they instead are mere projections that tell us more about the users of response-dependent concepts than about the world they inhabit. But even setting aside such extreme views, a number of important philosophical and psychological questions remain open. What exactly is response-dependence, and does any concept have this feature? What is the appropriate metaphysics for properties represented by response-dependent concepts, and for these concepts themselves? What determines the extension of such properties? How are we to account for knowledge expressed in terms of response-dependent concepts? What mechanisms correctly explain the origins of response-dependent concepts, and their role in representation?