This dissertation explores the relationship between the parser and the grammar in error-driven retrieval by examining the mechanism underlying the illusory licensing of subject-verb agreement violations (‘agreement attraction’). Previous work motivates a two-stage model of agreement attraction in which the parser predicts the verb’s number and engages in retrieval of the agreement controller only when it detects a mismatch between the prediction and the bottom-up input (Wagers, Lau & Phillips, 2009; Lago, Shalom, Sigman, Lau & Phillips, 2015). It is the second stage of retrieval and feature-checking that is thought to be error-prone, resulting in agreement attraction. Here we investigate two central questions about the processing system that underlies this profile. First, to what extent does error-driven retrieval end up altering the structural representation of the sentence, as compared to an independent feature-checking process that can result in global inconsistencies? Using a novel dual-task paradigm combining self-paced reading and a speeded forced choice task, we show that comprehenders do not misinterpret the attractor as the subject in agreement attraction. This indicates that the illusory licensing reflects a low-level number rechecking process that does not lead to restructuring. Second, what is the relationship between the information guiding the retrieval process and the terms that define agreement in the grammar? In a series of speeded acceptability judgment and self-paced reading experiments, we demonstrate that the number cue in error-driven retrieval is as abstract as the terms in which agreement is stated in the grammar, and that semantic features not relevant to the dependency in the grammar are not used to guide retrieval of the agreement controller. However, data from advanced Chinese learners of English suggests that it is not the case that all features relevant to the grammatical dependency will necessarily be used as retrieval cues. Taken together, these results suggest that the feature-checking repair mechanism follows grammatical principles but can result in a final structural representation of the sentence that is inconsistent with the grammar.