A Neural Theory of Language and Embodied Construction Grammar

This chapter outlines an explicitly neural theory of language and a construction grammar formalism based on this theory. The formalism, ECG, combines deep insights from cognitive linguistics with advanced techniques of neural computation. We illustrate the theory and the formalism with detailed, automatically generated semantic analyses of several related examples. Recent developments in neuroscience and the behavioral sciences suggest approaching language as a cornerstone of Unified Cognitive Science. One such integrative effort has been underway for two decades in Berkeley. The NTL (Neural Theory of Language) project studies language learning and use as an embodied neural system using a wide range of analytic, experimental, and modeling techniques. The basic motivation for NTL and its relation to ongoing experimental work is discussed in several places. The core idea is to take all the constraints seriously and to build explicit computational models that demonstrate the theoretical claims. At one level, NTL continues the tradition of Cognitive Linguistics (CL) represented by several chapters in this volume. But explicit computational modeling demands greater precision than is possible with the pictorial diagrams that remain standard in most CL work. CL and related approaches to language stress the continuity of language with the whole mind and body and with society. Statistical considerations and incremental learning and adaptation are also deemed essential parts of the capacity for language. The challenge is to develop a methodology that honors the inseparability of language use while being sufficiently rigorous to support formal and computational analysis. The NTL approach is to postulate distinct levels of description, explicitly mirroring the levels in the natural sciences such as biology, chemistry, and physics. The discussions in this chapter will focus on computational level descriptions of fairly complex language phenomena. In other work (Feldman 2006), we suggest how such descriptions can be reduced to a structured connectionist level and then to postulated brain structures. There is now a fair body of behavioral and biological experimentation exploring these models (Boroditsky 2000; Gallese 2005; Hauk 2004). Within the computational level, the NTL approach separates language understanding into two distinct phases called analysis and enactment. Schematically, analysis is a process that takes an utterance in context and produces the best fitting intermediate structure called the Semantic Specification or semspec (cf. Figure 6). The semspec is intended to capture all of the semantic 1 The ECGweb wiki can be found at http://ecgweb.pbwiki.com/. A web search using ECG NTL ICSI will also work.