A Discovery Procedure for Certain Phonological Rules

A DISCOVERY PROCEDURE FOR CERTAIN PHONOLOGICAL RULES Mark Johnson Linguistics, UCSD. ABSTRACT Acquisition of phonological systems can be insightfully studied in terms of discovery procedures. This paper describes a discovery procedure, implemented in Lisp, capable of deter- mining a set of ordered phonological rules, which may be in opaque contexts~ from a set of surface forms arranged in para- digms. 1. INTRODUCTION For generative grammarians, such as Chomsky (1965), a primary problem of linguistics is to explain how the language learner can acquire the grammar of his or her language on the basis of the limited evidence available to him or her. Chomsky introduced the idealization of instantaneous acquisition, which 1 adopt here, in order to model the language acquisition device as a function from primary linguistic data to possible gram- mars, rather than as a process. Assuming that the set of possible human languages is small, rather than large, appears to make acquisition easier, since there are fewer possible grammars to choose from, and less data should be required to choose between them. Accord- ingly, generative linguists are interested in delimiting the class of possible human languages. This is done by looking for pro- perties common to all human languages, or universals. Together, these universals form universal grammar, a set of principles that all human languages obey. Assuming that universal grammar is innate, the language learner can use it to restrict the number of possible grammars he or she must con- sider when learning a language. As part of universal grammar, the language learner is supposed to innately possess an evaluation metric, which is used to "decide" between two grammars when both are con- sistent with other principles of universal grammar and the available language data. 2. DISCOVERY PROCEDURES This approach deals with acquisition without reference to a specific discovery procedure, and so in some sense the results of such research are general~ in that in principle they apply to all discovery procedures. Still, I think that there is some util- ity in considering the problem of acquisition in terms of actual discovery procedures. Firstly, we can identify the parts of a grammar that are underspeeified with respect to the available data. Parts of a grammar or a rule are strongly data determined if they are fixed or uniquely determined by the data, given the require- ment that overall grammar be empirically correct. By contrast, a part of a grammar or of a rule is weakly data determined if there is a large class of grammar or rule parts that are all consistent with the available data. For example, if there are two possible analyses that equally well account for the available data, then the choice of which of these analyses should be incorporated in the final grammar is weakly data determined. Strong or weak data determination is therefore a property of the grammar formalism and the data combined, and independent of the choice of discovery procedure. Secondly, a discovery procedure may partition a phono- logical system in an …

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