Abstract:

Most languages of the world have a high proportion of morphologically complex words that are composed of two or more morphemes. When processing morphologically complex words, readers can choose to access the whole word meaning directly from the mental lexicon or to use morphological rules to construct the word semantics. Therefore, the exploration of the morphologically complex word processing mode could help us to promote the understanding of the language processing mechanism. In the past 30 years, the masked priming paradigm and lexical decision task have been widely used to study the mechanism of morphological complex words both in the first language (L1) and second language (L2) research. There is a consensus that native speakers could access the whole word meaning by combing morphemes, however, despite an increasing amount of second language research regarding this issue, the morphologically complex word processing mechanism for the late bilinguals who acquire the second language after the critical period (5 years old) is still in debate and shows a different pattern from native speakers. This mainly lies in two aspects: First, the morphological priming effect in the second language studies is very unstable, indicating that the ability of late second language learners to use morphological rules may be affected by many factors and the application of morphological rules is not as efficient as native speakers. Second, compared with native speakers, the late second language learners are more inclined to rely on the orthographic information than the morphological structure information in early word recognition, which is reflected by when the prime and target share the similar in orthography, there is no semantic competition between them to offset the promotion effect brought by the similarity of the orthography. Based on the Complementary Learning Systems account and Episodic L2 Hypothesis, the possible processing mechanism of L2 morphologically complex words is proposed and the divergence of previous L2 research is explained under this theoretical framework. We propose that different from native speakers, the late bilinguals mainly acquire the second language knowledge in an explicit way (i.e., classroom introduction), which may lead to the abstract morphological information in the neocortex is not formed. Therefore, when late second language learners process complex morphological words, the abstract morphological rules through the neocortical mechanism could not be used to promote the morphologically complex words’ processing, but a temporary morphological rule through the hippocampal mechanism could be involved in this process. Since the extraction of morphological rules through the hippocampus mechanism needs to be reconstructed and then real-time reconstruction of morphological rules takes a certain amount of time, which leads to the instability of the morphological priming effect and the lower efficiency of the application of the morphological rules. In addition, according to the Episodic L2 Hypothesis, for late second language learners, words are stored in the episodic memory system where these representations are irrelevant. Therefore, there is no competition at the meaning level between the prime and target when they are similar in orthography, which also explains why there is a significant from priming effect for the late L2 learners at least in lexical decision task. The evidence from the cognitive neuroscience area is needed to test the rationality of our hypothesis in the future. Secondly, eye movement techniques could be adopted in future research to investigate the processing mechanism of morphologically complex words for second language learners under more natural reading conditions. Finally, future research also needs to explore the influences of morphological family size on the processing of L2 morphologically complex words, as well as reveal the neural mechanism underlying L2 morphologically complex words. 

Key words: second language learner, morphologically complex words, processing mechanism, morphological rule