Models of Lexical Decay

15 1965 International Conference on Computational Linguistics MODELS OF LEXICAL DECAY D. Kleinecke TECHNICAL MILITARY PLANNING OPERATION GENERAL ELECTRIC COMPANY 735 State Street (P. O. Drawer QQ) SANTA BARBARA, CALIFORNIA 9310Z Abstract Lexical decay is the phenomenon underlying the dating tech- niques known as "glottochronology" and"lexicostatistics." Much of the contraversial nature of work in this field is the result of extremely imprecise foundations and lack of attention to the underlying statistical and semantic models. A satisfactory semantic model can be found in the concept of se- mantic atom. Notwithstanding a number of philosophical objections, the semantic atom is an operationally feasible support for a lexicon which is a semantic subset of all possible meanings and at the same time, exhausts the vocabulary of a language. Lexical decay is the process by which the lexical item covering an atom is replaced by another lexical item. Exponential lexical preservation is, in this model, directly analogous to decay phenomena in nuclear physics. Consistency re- quires that the decay process involved in exponentially preserved vocabularies be a Poisson process. This shows how to form test vocabularies for dating and proves that presently used vocabularies are not correctly formed. Dialectation studies show that historically diverging populations must be modelled by correlated Poisson processes. Definitive sta- tistical treatment of these questions is not possible at this time, but much desirable research can be indicated. Kleinecke - I Introduction This paper is an attempt to establish the method of dating by lexical decay upon an adequate theoretical foundation. The method discussed is that invented by Swadesh (1) over a decade ago and usually known as glottochronology or lexicostatistics. In the inter- vening years it has been widely applied, but often to the accompa- niment of much confusion and contraversy. It seems that much of the confusion can be removed by a rigorous treatment of the phenom- enological model and careful application of statistics. The contraversy can be removed only by the completion of a sufficient number of supporting studies. Rigorous formulation permits us to'pinpoint what studies are needed and what conclusions are being sought. Granting (as not everyone seems willing to do) that the basic fact of "uniform" lexical decay occurs, the problem to be attacked is that of correctly formulating models for lexical decay and of correctly deriving statistical consequences from these models. In what follows, we will construct a set of models which seem to fit the needs of the method of dating by lexical decay, Our approach is strictly pragmatic, that is, we construct the model we need with- out concerning ourselves about its a priori reasonableness. Later we try to assemble some arguments which justify the model. In no sense is this an approach for first principles. The analogy between lexical decay and the decay phenomena of nuclear physics has been often noted and dismissed. In the pre- sent paper, we insist that this analogy is much more than an analogy; it is, on the first level, an identity. The only alternative to …

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