The present dissertation research investigates how morphologically complex words are processed in isolation and in sentential context by native speakers and second language learners, and how four critical factors in morphological processing (regularity, stem frequency, whole-word frequency, and orthographic similarity) influence this processing.

For comparisons between different first languages (Korean L1 and English L1) and between first and second languages (English L1 and English L2), Native Korean Speakers (Exp.1 and 3), Native English Speakers (Exp. 2a and 4a), and Korean Learners of English (Exp. 2b and 4b) were tested. In order to compare the priming effects from words in isolation and words in sentences, sets of inflectional prime and target pairs, one for each language, were used both in a masked priming lexical decision task (Exp.1 and 2) and a self-paced reading task with mask priming (Exp. 3 and 4).

The results showed priming effects from inflectional prime and target pairs in both Korean L1 and English L1 when the pairs were presented in isolation, showing morphological sensitivity in both L1 groups. However, when the pairs were embedded in sentences, the priming effect was found only in native English speakers but not in native Korean speakers, implying language-specific differences between Korean and English in processing of inflectional words in sentences. Moreover, even though a similar pattern of priming effects was found for words in isolation, English L2 showed no significant priming effect for words in sentences, consistent with past literature demonstrating less sensitivity to morphological structure in L2. The different patterns of priming effects between the two tasks as well as across the three language groups in the present research were also analyzed in terms of the four morphological factors, and discussed from the perspective of language-specific characteristics.

In summary, the present dissertation research examined morphological processing of two typologically different languages in two different reading contexts. The results suggest the importance of language-specific characteristics in various reading conditions in enhancing our understanding of morphological processing in the human mind.