The goal of this paper is to tease apart two approaches to the source of children's consistent scope assignment in negative sentences containing logical connectives: the Semantic Subset Principle and the Semantic Subset Maxim. Previous developmental work has observed that four- to six-year-old children across languages have difficulty with disjunctive interpretations in these sentences and assign conjunctive interpretations. The results of our experiment however show that Japanese children can access the disjunctive interpretations when conjunctions are elided. This finding supports the idea that children are guided by the Semantic Subset Principle when determining the default value of any parameter associated with a logical connective.