According to the text “errors” are:

Before the 1960’s, during the dominance of the behaviouristic view upon language there existed a dominated view of language to consider learners’ errors as something undesirable. Making errors was seen as a sign of mislearning and regarded as undesirable to proper processes of language learning. According to the behaviouristic point of view, the reason behind making errors lies in inadequate teaching methods which if had been “perfect” they would never be committed. This way of thinking was considered to be naive as there is nothing to be called “perfect” methodology especially with the appearance of the Universal Grammar concept proposed by Chomsky in 1965. The latter claimed that each human being has an innate capacity that can guide him through a vast number of sentence generation possibilities. Since then, a shift by language teachers towards the cognitive approach has started. Chomsky’s theory contributes in raising researcher’s interests about learners’ errors as a source of hypotheses formation. The importance of errors in language learning was first advocated by Corder (1967). He proved that strategies of L2 learners could be inferred through the analysis of their errors and that could be helpful for researchers of L2 learning process. Selinker (1992) highlighted two fundamental contributions of Corder’s study in L2 learning. The first one is that the learner’s errors are systematic and the second is that they are not “negative” or “interfering” but a positive factor, indicative of testing hypothesis.

Errors Correction in Foreign Language Teaching . Available from: https://www.researchgate.net/publication/318249645_Errors_Correction_in_Foreign_Language_Teaching [accessed Aug 6, 2017].