In the face of underspecified utterances, listeners routinely and without much apparent effort make the right kinds of pragmatic inferences about a speaker's intended meaning. This dissertation investigates the processing of scalar implicatures as a way of addressing how listeners perform this remarkable feat. In particular, the role of context in the processing of scalar implicatures from "some" to "not all" is explored. Contrary to the widely held assumption that scalar implicatures are highly regularized, frequent, and relatively context-independent, this dissertation suggests that they are in fact relatively infrequent and highly context-dependent; both the robustness and the speed with which scalar implicatures from "some" to "not all" are computed are modulated by the probabilistic support that the implicature receives from multiple contextual cues. Scalar implicatures are found to be especially sensitive to the naturalness or expectedness of both scalar and non-scalar alternative utterances the speaker could have produced, but didn't. A novel contextualist account of scalar implicature processing that has roots in both constraint-based and information-theoretic accounts of language processing is proposed that provides a unifying explanation for a) the varying robustness of scalar implicatures across different contexts, b) the varying speed of scalar implicatures across different contexts, and c) the speed and efficiency of communication. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]