Human communication relies on the ability to assess what others intend to communicate beyond what they directly say. Under classic theories of communication, a critical component of this process is the evaluation of what another person knows (epistemic reasoning) and how that knowledge will affect the value of what they communicate. For example, a sentence such as "Some tires need to be replaced after 50,000 miles" can be interpreted as giving rise to the inference "Some but not all tires need to be replaced after 50,000 miles" when uttered by an expert. However, the same inference does not arise when the sentence is spoken by a 16-year-old driver with limited knowledge about tires. Adults have been shown to adjust the inferences they make during communication in accordance with the knowledge state of the speaker, but in young children this ability is debated. This dissertation explores the role that epistemic reasoning plays in the development of pragmatic inferences in both linguistic and non-linguistic communicative contexts using behavioral and neural approaches. In a series of studies, we investigate whether young children are capable of making sensitive adaptions to the epistemic state of a communicator during pragmatic inference. We use variations on a novel visual world paradigm in a carefully chosen set of contexts to explore how young children develop scalar inference competence and how that development interacts with the development of epistemic reasoning. First, we focus our attention on 4- and 5-year-old children to address existing debates over the role of epistemic reasoning in early derivation of scalar implicatures. Next, we examine how expectations of informativeness and other communicative principles extend to forms of ostensive communication using non-linguistic symbols. Finally, we employ neuroimaging methods to look through a different lens at the relationship between pragmatic development and epistemic development. These finding contribute not only to our understanding of scalar implicatures, but also to the broader fields of pragmatics, theory of mind, symbolic development, and cognitive neuroscience. [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.]