The purpose of this paper is to review the cognitive literature regarding transfer in order to provide a context for the consideration of transfer in neural networks. We consider transfer under the three general headings of analogy, skill transfer and metaphor. The emphasis of the research in each of these areas is quite different and the literatures are largely distinct. Important common themes emerge, however, relating to the role of similarity, the importance of "surface content", and the nature of the representations that are used. We will draw out these common themes, and note ways of facilitating transfer. We also briefly note possible implications for the study of transfer in neural networks.