This dissertation interrogates the representation of syntactic locality constraints, specifically intervention locality, within child grammar. Our focal point is the Intervention Hypothesis, which suggests that children are governed by a strict version of featural Relativized Minimality, leading to comprehension difficulties when partial featural overlap between moved elements and interveners is present. The unique morphosyntactic properties of Mandarin "bei"-passives afford an ideal platform for our investigation. Syntactic investigations indicate that long "bei"-passives involve movement of the internal argument (IA) across the external argument (EA), which is an embedded subject in this construction, whereas the IA movement in short "bei"-passives does not cross an EA because the EA is not syntactically projected. As such, the IA movement in long "bei"-passives, demonstrated in (1a), provokes intervention, which, based on the Intervention Hypothesis, should cause more difficulty for children's comprehension than short "bei"-passives (1b). Furthermore, unlike in English, Mandarin lacks verbal/adjectival passive homophones to facilitate children's comprehension of short passives. Consequently, children must establish a dependency between the IA and its gap, necessitating crossing an intervening argument in long passives. Our corpus study shows that long "bei"-passives are more frequent than short "bei"-passives in both child spontaneous speech and their input, which is not observed in any other languages in previous literature. In line with the Intervention Hypothesis, our results from both Experiments 1 and 2 highlight that children's comprehension of long passives is worse than short passives, despite their significantly higher frequency in child and child-directed Mandarin. The dissertation further investigates which features are computationally relevant for intervention in child grammar. By manipulating three distinct features in Mandarin -- Animacy, Number, and Shape -- our research illuminates the role of linguistic features in forming a syntactic dependency. Experiment 1 shows that Animacy mismatch improved children's performance on long passives, indicating its participation in children's computation of intervention. An alternative ex- planation exists for this effect, however. Experiment 2 shows that a mismatch in Number or Shape does not affect children's intervention difficulty with long passives. This leads us to propose that only morphosyntactic features triggering syntactic movement play a role in calculating intervention locality. In summary, this dissertation provides evidence supporting the Intervention Hypothesis, underscoring the intervention difficulty in children's comprehension of long, but not short, "bei"-passives. Our research suggests that only morphosyntactic features triggering syntactic movement participate in computing intervention locality. This discovery introduces new dimensions to our understanding of syntactic locality constraints in child grammar and exposes cross-linguistic variations in the engagement of different morphosyntactic features in this aspect.[Equations Omitted.]. [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.]