Abstract

It is a controversial issue as to which of the two approaches, the Physical Symbol System Hypothesis or Parallel Distributed Processing , is a better characterization of the mind. At the root of this controversy are two questions: What sort of computer is the brain, and what sort of programs run on that computer? What is presented here is a theory which bridges the apparent gap between PSSH and PDP approaches. In particular, a computer is presented that adheres to constraints of PDP computation , and a program is presented which at first glance is only suitable for a PSSH computer but which runs on a PDP computer. The approach presented here, vertical integration, shows how to construct PDP computers that can process symbols and how to design symbol systems so that they will run on more brain-like computers. ;The type of computer presented here is called a tensor manipulation network. It is a special type of PDP network where the operation of the network is interpreted as manipulations of high rank tensors . The operations on tensors in turn are interpreted as operations on symbol structures. A wide range of tensor manipulation architectures are presented with the goal of inducing constraints on the symbol structures that it is possible for the mind to possess. ;As a demonstration of what is possible with constrained symbol structures, a program, CRAM, is presented which uses and acquires thematic knowledge. CRAM is able to read, in English, single-paragraph, fable-like stories and either give a thematically relevant summary or generate planning advice for a character in the story. CRAM is also able to learn new themes through combination of existing, known themes encountered in the fables CRAM reads. ;CRAM demonstrates that even the most symbolic cognitive tasks can be accomplished with PDP networks, if the networks are designed properly