Speaker's sensitivity to three types of rule violations in sentences was examined with a method of factor analysis to explore whether three factors corresponded to the three types of violation. The types of violation used involved a rule of lexical category, selectional restriction on a phrase boundary and selectional restriction on a noun phrase. Results showed that while two factors mostly corresponded to the first and third rule violation were obtained, they did not fully represent the pre-assigned items. A factor for the second rule violation could not be identified. The study findings were discussed in relation to Chomsky's contention that native speakers of a language possess the linguistic ability to judge grammaticality in their native language.