Scope ambiguity arises when a sentence contains scope-bearing logical operators like quantifiers and negation (Fox, 2003). For instance, in English, the sentence 'Every horse didn't jump over the fence' can be interpreted as either 'None of the horses jumped over the fence' (surface scope) or 'Not all of the horses jumped over the fence' (inverse scope). Chinese exhibits a scope-rigid nature, arguably permitting only surface scope readings (Aoun & Li, 1989; Huang, 1982). Furthermore, English-speaking learners of Chinese would presumably encounter the well-known poverty-of-the-stimulus (POS) problem (Pearl, 2021; White, 2022) due to the lack of positive evidence in the L2 input. This study utilized a bidirectional design to investigate the offline interpretation and online processing of quantifier scope by L2 learners of English and Chinese. Three experiments involving doubly quantified and negatively quantified sentences were conducted, marking the first investigation of its kind. In Experiment 1 with sentence-interpretation matching tasks, both English and Chinese speakers predominantly favored surface scope interpretations without supportive discourse contexts. Notably, English speakers leaned more towards accepting inverse scope interpretations, except for NU sentences. In Experiment 2 involving L2 learners of English and Chinese, results from truth-value judgment tasks demonstrated their target-like acquisition of quantifier scope interpretations across most structures. In Experiment 3, employing the visual-world eye-tracking paradigm with the same participants, the findings closely paralleled those of Experiment 2, especially regarding the observed patterns in eye-fixation data. This cross-linguistic study advances empirical research on L2 learners' quantifier scope interpretation, revealing their capacity to largely surmount the POS problem. Acquisition patterns were shaped by factors including L2 (triggering) input, grammatical constraints, L1 transfer, L2 proficiency, statistical inference, and experimental setups. Another novel discovery is that Chinese exhibits the ability to obtain inverse scope interpretations for NU sentences across experiments, challenging the long-standing scope-rigidity claim associated with this language. This compelling evidence indicates that scope rigidity in Chinese may not be universally applicable, and certain interpretations that were previously assumed to be unavailable can be facilitated by factors like discourse contexts or experimental setups. Therefore, NU sentences are not a POS problem for learners of L2 Chinese. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]