[4] In 1987, she and linguistics researcher Steven H. Weinberger were co-editors of the book Interlanguage Phonology: The Acquisition of a Second Language Sound System (Newbury House Publishers).
A 1990 review of this book in Second Language Research called it a "well integrated, comprehensive mixture of established and recent articles, covering all major issues of phonology.
"[5] Ioup was the primary author of "Reexamining the Critical Period Hypothesis: A Case Study of Successful Adult SLA in a Naturalistic Environment," published in March 1994 in the journal Studies in Second Language Acquisition, which examined "the ability of adults to achieve nativelike competence in [a] second language" without the benefit of formal schooling.
"[1] In the interview, Ioup explained that while teaching in Egypt, she had met a British student, Julie, who reported learning Egyptian Arabic "as an adult but in the manner of a child," meaning the student never had formal training in Egyptian Arabic and could only speak the language, not read or write it.
[1] Ioup recounted that this student's ability to learn Egyptian Arabic led Ioup to reconsider the so-called critical period hypothesis, which claims that languages need to be learned at a young age (usually before puberty) in order to achieve nativelike fluency.