tailieunhanh - Báo cáo khoa học: "Co-evolution of Language and of the Language Acquisition Device"

A new account of parameter setting during grammatical acquisition is presented in terms of Generalized Categorial G r a m m a r embedded in a default inheritance hierarchy, providing a natural partial ordering on the setting of parameters. Experiments show that several experimentally effective learners can be defined in this framework. Ew)lutionary simulations suggest that a with default initial settings for parameters will emerge, provided that learning is memory limited and the environment of linguistic adaptation contains an appropriate language. . | Co-evolution of Language and of the Language Acquisition Device Ted Briscoe ejb@ Computer Laboratory University of Cambridge Pembroke Street Cambridge CB2 3QG UK Abstract A new account of parameter setting during grammatical acquisition is presented in terms of Generalized Categorial Grammar embedded in a default inheritance hierarch providing a natural partial ordering on the setting of parameters. Experiments show that several experimentally effective learners can be defined in this framework. Evolutionary simulations suggest that a learner with default initial settings for parameters will emerge provided that learning is memory limited and the environment of linguistic adaptation contains an appropriate language. 1 Theoretical Background Grammatical acquisition proceeds on the basis of a partial genotypic specification of universal grammar HG complemented with a learning procedure enabling the child to complete this specification appropriately. The parameter setting framework of Chomsky 1981 claims that learning involves fixing tin values of a finite set of finite-valued parameters to select a single fully-specified grammar from within the space defined by the genotypic specification of UG. Formal accounts of parameter setting have been developed for small fragments but even in these search spaces contain local maxima and subset-superset relations which may cause a learner to converge to an incorrect grammar Clark 1992 Gibson and Wexler 1994 Niyogi and Berwick 1995 . The solution to these problems involves defining default unmarked initial values for some parameters and or ordering the setting of parameters during learning. Bickerton 1984 argues for the Bioprogram Hypothesis as an explanation for universal similarities between historically unrelated creoles and for the rapid increase in grammatical complexity accompanying the transition from pidgin to creole languages. From the perspective of the parameters framework the Bioprogram Hypothesis claims