Researchers have found a very consistent order in the acquisition of first-language structures by children, which has drawn interest from Second Language Acquisition (SLA) scholars. Considerable effort has been devoted to testing the "identity hypothesis", which asserts that first and second language acquisitions may conform to similar patterns. This, however, has not been confirmed, perhaps because second-language learners' cognition and affect states are more developed. The two may have common neurological bases, but no convincing scientific evidence supports this hypothesis. Brown (1973) conducted a study on the acquisition of 14 grammatical morphemes by three English-speaking children and found that their developmental patterns were remarkably similar. This study is said to have initiated research in the field of SLA to investigate whether the patterns of L1 and L2 acquisition are also similar. Dulay and Burt produced a highly cited and classic study in this area. They investigated the acquisition order of eight grammatical morphemes (progressive -ing, plural -s, irregular past tense, possessive 's, articles, third-person singular -s, copula be, and auxiliary be) among children learning English as a second language. Their study included 95 Mexican-American children, 26 Spanish-speaking children, and 30 Puerto Rican children. The researchers predicted that the three groups would exhibit the same acquisition order, but that this order would differ from what is observed in first language acquisition. This was based on the assumption that the semantic distinctions second language learners already possess would influence the mapping of semantic functions to morphemes. Followed by studies that showed similar patterns for L2 acquisition, the view that the order of morpheme acquisition of English is consistent and relatively independent of the
L1 has been dominant ever since, but recent studies have expressed results that challenge this view, and maintain that the morpheme acquisition order is at least partly L1-dependent. to this claim. For example, these are reviewed by Ellis. They show that learners begin by omitting pronouns or using them indiscriminately: for example, using "I" to refer to all agents. Learners then acquire a single pronoun feature, often person, followed by number and eventually by gender. Little evidence of interference from the learner's first language has been found; it appears that learners use pronouns based entirely on their
inferences about target language structure. More recent studies have shown that universality and individuality coexist in the order of grammatical item acquisition. For example, a large-scale investigation In both fields, consistent patterns have emerged and have been the object of considerable theorizing. == See also ==