he past tense has been the source of considerable debate concerning the role of connectionist models in explaining linguistic phenomena. In response to Pinker and Prince (1988), several connectionist models have been developed that compute a mapping between the present tense phonological form of a verb to a past tense phonological form. Most of these models cannot distinguish between homophones such as F L Y - F L E W and FLY-FLffiD (as in "flied out"). Kim. Pinker, Prince, & Prasada (1991) have suggested that the addition of semantic information to such nets will not provide an adequate solution to this homophony problem. They showed that English speakers use derivational status, rather than semantic information in generating past tenses. W e provide evidence contradicting this account. Subjects' rated preferences for past tense forms are predicted by semantic measures; moreover, a simulation model shows that semantic distance provides a basis for learning the alternative past tenses for words such as F L Y . W e suggest a reconciliation of the two theories in which knowledge of "derivational status" arises out of semantic facts in the course of learning.

MacDonald, Pearlmutter, and Seidenberg (1993) propose an alternative to the dominant view in sentence processing that syntactic ambiguities are resolved by heuristics based on structural simplicity. MacDonald et al. argue that such ambiguities can be defined in terms of alternatives associated with information in individual lexical items, and thus that syntactic ambiguities can be resolved by lexical disambiguation mechanisms relying on access to the relative frequencies of alternatives and to biases created by contextual constraints. We present evidence from a computer simulation of the use of frequency-based and contextual constraints in the processing of the main verb/reduced relative syntactic ambiguity, showing that frequency and relatively limited contextual information from a sample of natural language can interact sufficiently to model basic results in the literature.