When starting school pupils begin to adopt the standard Croatian language (non dominant L2), which in some regions differs from the native idioms (dominant L1). In this situation the interlanguage field is created and most students become vertically plurilingual, i.e. the interweaving of different language codes is ref lected in monolingual school practice.In this research the greatest attention has been paid to the cognitivelinguistic para digm and the constructivist theory, within which the stimulus theory and error theory have proven to be an extremely purposeful part of the learning process in the early lan guage development. The aim was to examine the purposefulness of the application of the modern learning theories on the development of communicative competence of younger primary school pupils. The research results have confirmed that communicative compe tence can be successfully developed, among other, by taking advantage of errors as a stim ulus for further learning. Only in such a situation the interlanguage field in monolingual Croatian language practice should be treated as a positive and not a negative linguistic phenomenon.