For many students, basic understanding of grammar comes from "hearing" written text in their heads. If you ask a student how he or she spotted a grammatical error, the answer is often, "It didn’t sound right." For subject-verb agreement, contractions, punctuation, and other basic grammar topics, this strategy is quite effective. However, for the more complex grammar required in AP English or college-level English, "hearing" is no longer sufficient. Identifying dangling modifiers, types of phrases, and parts of a sentence require an intellectual understanding of the subject.