Is first language attrition possible without second language knowledge?

The study explores whether Russian immigrants in Israel with no knowledge of Hebrew (L2) can experience attrition of Russian (L1). Immigrants with no knowledge of Hebrew (-Hebrew), bilingual immigrants who know Russian and Hebrew (+Hebrew), and monolingual controls were compared on lexical retrieval, correctness judgment of collocations, future tense formation, confidence in providing answers to two tasks and the time it took to complete them. Both immigrant groups showed signs of L1 attrition of collocations and of future tense formation, and the -Hebrew group performed significantly worse than +Hebrew group on future tense formation. The three groups did not differ in time-on-task. The -Hebrew group was less confident than the other groups in one task. Low and significant correlations were found between some sociolinguistic factors and test results. We conclude that first language attrition can occur both when immigrants acquire a second language and when they remain monolingual.