This paper explores whether witnessing a Virtual Human (VH) in what appears to be a socially engaging discussion with another virtual human confederate/accomplice (VHC) can prime a person to feel and behave more socially engaged with the VH in a subsequent interaction. To explore this social priming phenomenon, we conducted an experiment in which participants in a control group had no priming while those in an experimental group were briefly exposed to an engaging social interaction between a VH and a nearby VHC. The participants primed by exposure to the brief VHC-VH interaction reported being significantly more excited and alert, perceiving the VH closer, and showed significantly higher measures of Co-Presence, Attentional Allocation, and Message Understanding dimensions of social presence towards the VH, compared to those who were not primed.