. Where do perceptually grounded categories come from? Some researchers claim they are innate, others claim they are learned. This paper presents a third 'ecological' approach. I propose a system by which discrimination networks, capable of categorial distinctions, spontaneously grow, rather independently of specific examples. I show that linguistic interaction can drive a spiraling increase in the ontological complexity of an agent. The ontology formation mechanism can be coupled to adaptive language games by which a shared lexicon spontaneously self-organises. Software simulations and experiments with robotic agents serve as examples. 1 Introduction The past few years, a number of researchers have become interested in building operational theories for how language and the conceptualisation of reality that underlies language can bootstrap itself, both in a developing single individual (ontogenesis) and in the human species (glossogenesis); (Hurford, 1989), (Steels, 1979b), (..