Experiment 4 acceptability fixed effects.

We present four experiments investigating adaptation to a regional grammatical structure through reading exposure, using both the needs + past participle construction (e.g., The car needs washed) and the double modal construction (e.g. You might could go there). In each experiment, participants read two stories containing informal dialogue. Half of the participants were exposed to one of the regional constructions and half were not. Those readers exposed to the regional constructions adapted, gradually reading the novel constructions faster over 9 to 15 exemplars. The degree to which the exposed group learned the construction was tested in two ways. In the first two experiments, learning was measured by comparing reading times to acceptable and unacceptable variants of the novel constructions. Readers did not learn either the verb tense rule for the needs construction (Experiment 1) or a simple ordering rule for double modal constructions (Experiment 2). Similarly, in Experiments 3 and 4, metalinguistic judgments used to test learning revealed that participants had failed to acquire the regional grammar of either novel construction. These experiments suggest that the adaptation effects reflect learning some general properties of the experimental stimuli, not learning the syntactic constructions themselves.