Ambiguity, parsing, and the evaluation measure

An evaluation measure (EM) guides a learner's choice of grammar when more than one is compatible with available input. EM must be universal, so children receiving comparable input acquire comparable grammars. It must favor the choices children actually make. The theoretical shift from rule-based grammars to principles-and-parameter-based grammars demanded a new conception of EM. I propose that it reflects biases of the sentence processing mechanism.