The document summarizes a study on the generalization of relative clauses in English as a second language. The study tested 36 students learning English who were divided into four groups receiving different types of instruction on relative clauses. The groups focused on subject, direct object, object of preposition, and received no instruction. Post-tests showed students learned the types taught best and generalized learning to less marked structures, supporting the markedness differential hypothesis that more marked structures are harder to learn. The study provides evidence that universal grammar can influence adult second language acquisition, at least for relative clause formation.