Investigating the Relationship between the Morphological Processing of Regular and Irregular Words and L2 Vocabulary Acquisition

The present study investigates the relationship between the morphological processing of regular and irregular words and second language (L2) vocabulary acquisition. In considering that monolingual Arabic speakers derive a large number of new words from roots by leaning heavily on the regularity of rules in Arabic (Bar Dershowitz, 2012; Habash, 2010), they are expected to experience difficulty when developing the lexicon of a language with less regular rules, such as English. To examine this assumption empirically, data were collected by administering an English receptive vocabulary knowledge test that included 100 regular and irregular inflected and derived words to 450 Arabic English as a foreign language (EFL) learners from schools in Saudi Arabia. The test also included pesudowords (nonwords) to act as ‘gatekeepers’ against the possibility of guessing. The t-test results revealed a non-significant difference in learners’ uptake of L2 words, whether regular or irregular. However, the study indicates that word frequency plays a statistically significant role in learning L2 vocabulary that is irregularly inflected or derived. The frequency effect on irregular word morphology found in this study is in line with the approach of a dual-route mechanism. This approach suggests that irregular words are not rule-based, so are stored in the mental lexicon as full entries, whereas regular words are not. This article suggests that introducing rules for deriving new words from base forms to EFL learners in the early stages of learning would be very useful for L2 vocabulary development.