Previous research on Arabic heritage speakers points to notable variability in the language proficiencies of Arabic heritage speakers, both as individuals and as groups (Albirini & Benmamoun, 2012; Albirini, Benmamoun, & Saadah, 2011). This study examines the language proficiencies of Egyptian and Palestinian heritage speakers, assesses the relationship between their L1 proficiency levels and other linguistic, socio-affective, socio-contextual, and demographic factors, and explores the relative significance of these factors in determining proficiency in heritage Arabic. A total of 20 Egyptian and 20 Palestinian heritage speakers completed an oral narrative that was used for assessing three dimensions of their language proficiencies, namely fluency, grammatical accuracy, and syntactic complexity. In addition, the participants filled in a 182-item questionnaire about the factors potentially influencing their heritage language skills, including language input, language use, language attitudes, ethnic identity, family role, community support, school, and demographics. The study also involved follow-up interviews with a sample of five Palestinian and five Egyptian participants.

The results showed that the Palestinian speakers outperformed their Egyptian counterparts in terms of language fluency, accuracy, complexity, and overall proficiency. Pearson and Spearman correlations indicated that language use, language input, family role, community support, and parents’ language correlate positively with language proficiency. Multiple regression analyses showed that language use (in terms of frequency, range, and contexts) is the only significant predictor of the variability in heritage language proficiency. Lastly, the interviews revealed that the Palestinian heritage speakers’ linguistic advantage over their Egyptian counterparts might be attributed to their commitment to Arabic as a main marker of their heritage and identity, the encouragement of their families to maintain their heritage language, and the wider social networks to which they had access. The implications of the study are discussed.