This study examines the sensitivity of Saudi Arabian learners of English as a Foreign Language (EFL) to grammatical violations of article use in (non-)referential indefinite contexts. The Morphological Congruency Hypothesis (MCH) predicts online sensitivity to ungrammaticality when both languages grammaticalize a shared meaning. Although Arabic and English both grammaticalize definite/indefinite meanings, they differ in morphological marking. English marks indefiniteness with an overt article, while Arabic marks it by a lack of article, and has an optional indefinite referential marker, wa:ħid ‘one’. In two experiments, on article omission and article misuse respectively, the study employed online self-paced reading and offline grammaticality judgment tasks. The results challenge the MCH, showing that Arabic EFL learners are sensitive to article omissions before indefinite singular count nouns but less sensitive to article misuse in the same environment. The lack of sensitivity to article misuse occurred with referential indefinites, suggesting the possibility of transfer effects of the Arabic referential marker.
