This study is part of a longer-term project to provide embodied conversational agents (ECAs) with behaviors that enable them to build and maintain rapport with their human partners. We focus on paralinguistic behaviors, and especially nonverbal behaviors, and their role in communicating rapport. Using an ECA that guides its players through a speech-controlled game, we attempt to measure the familiarity built between humans and ECAs across several interactions based on paralinguistic behaviors. In particular, we studied the effect of differences in the amplitude of nonverbal behaviors by an ECA interacting with a human across two conversational sessions. Our results suggest that increasing amplitude of nonverbal paralinguistic behaviors may lead to an increased perception of physical connectedness between humans and ECAs.