The development of L2 morphology

According to the Declarative/Procedural model (Ullman, 2005) and the Shallow Structure Hypothesis (Clahsen and Felser, 2006), late L2 learners do not decompose morphologically complex words; rather, adult L2 learners store inflected words as whole word forms in the mental lexicon (Step 1). [...]on the assumption that the L1 settings initially informs L2 grammars (Full Transfer/Full Access Hypothesis; Schwartz and Sprouse, 1996), L2 learners need to reassemble grammatical and interpretable features that govern the distribution of inflectional forms (Feature Reassembly Hypothesis; Lardiere, 2009). [...]Montrul, de la Fuente, Davidson and Foote observe that age differences between child and adult learners correlate with differences in the type of input available to learners. In order to test the relative contributions of age and input differences, the authors compare adult L2 learners with early L1 heritage learners. Since heritage learners receive early target-language input, they are likely to have been exposed to more diminutives than adult L2 learners even though, like adult L2 learners, they often only reach intermediate to advanced proficiency levels in the target language.