The present investigation tests the predictions of the Interpretability Hypothesis (Tsimpli & Dimitrakopoulou, 2007), according to which uninterpretable features are subject to L1-based maturational effects, representing an insurmountable difficulty in adult L2 acquisition. The study tests knowledge of gaps vs. resumptive pronouns in L2 English by native speakers of Kuwaiti Arabic. Results show that the experimental L2 groups showed evidence of successfully differentiating ungrammatical questions with a resumptive pronoun and grammatical questions without one. More importantly, however, results did not provide any evidence that interpretable features (e.g., animacy or d-linking) aided development. These results do not support the predictions of the Interpretability Hypothesis. However, given that the study did not involve time-sensitive measures, it is an open question whether these conclusions would hold under time pressure.