Recent years have seen an explosion of research in neural networks, or what has become more generally known as connectionism. The roots of connectionism can be found in many disciplines, giving the area a strength due to the many fields that it intersects and a weakness in that the connectionism seems diffuse and ill-

defined. Much of what amounts to the central issues in connectionist research (cf. Hanson & Burr, 1990) finds a comfortable home in the cognitive science field, which is itself a mixture of computer science, psychology, philosophy, linguistics and other fields. Nonetheless, despite this apparent diversity, the roots of connectionism are deeply and uniquely entwined with psychology and in particular animal learning theory.