Corpus evidence and the role of probability estimates in processing decisions

An exception to a non-categorical generalization consists of a lexical item that exhibits the general pattern at a rate radically different – either far higher or far lower – from the norm. Lexical differences in noun phrases containing non-subject relative clauses (NSRCs) correlate with large differences in the likelihood that the NSRC will begin with that. In particular, the choices of determiner, head noun, and prenominal adjective in an NP containing an NSRC may dramatically raise or lower rates of that in the NSRC. These lexical variations can be partially explained in terms of predictability: more predictable NSRCs are less likely to begin with that. This generalization can be plausibly explained in terms of processing, assuming that facilitates processing and/or signals difficulty. The correlations between lexical choices in the NP and the predictability of an NSRC can, in turn, be explained in terms of the semantics of the lexical items and the pragmatics of reference.