Second-language teachers are concerned with the cause and elimination of errors in second-language classes. Until recently, most linguists believed that errors were due to interference from the mother tongue. On this basis, they placed a great deal of importance on contrastive analysis. The feeling was that if linguists could analyze carefully and completely the systems of both the first and the second languages, they would be able to predict the errors that would occur during second-language learning. This theory was based on the tenet that language was primarily a set of conditioned verbal habits. Errors in second-language learning would occur at those points at which the two language systems were dissimilar. The solution was a systematic analysis of both languages followed by the prescription of pattern drills to overcome first-language habits.
Recent investigations of the errors made by second-language learners have revealed surprising statistics. Although some errors are the direct result of native-language interference, the percentage is not so large as had been believed. The errors tabulated by Dulay and Burt (1973) indicated that only 3 percent of the errors in their study were due to interference. Hanzeli (1975, p. 8) states that researchers in contrastive analysis ". . . like Corder, Selinker, Burt, and George, have proved conclusively that the traditional contrastive analysis of two grammars cannot predict the frequency and hierarchy of learners' errors."