Processing trimorphemic words in a second language:effects of exposure type

A central question in second language (L2) acquisition is whether L2 processing can become nativelike. The Shallow Structure Hypothesis (SSH) posits morphological processing in L2 is qualitatively different from that of L1, whereas the Declarative/Procedural (D/P) Model suggests naturalistic exposure (NE) to L2 can lead to nativelike processing. This study investigated whether L2 morphological processing can become nativelike by examining L1-Persian learners of L2-English with classroom exposure (CE) and those with NE. Using a cross-modal priming task, we presented trimorphemic English words under three different priming conditions: constituent (rewash → rewashable), nonconstituent (washable → rewashable), and unrelated (notify → rewashable). The NE group exhibited stronger priming in the constituent than in the nonconstituent condition, while the CE group showed equal priming in both conditions. The CE group’s performance aligns with the SSH, whereas the NE group demonstrated nativelike processing, supporting the D/P Model and highlighting the importance of NE.