Conversation partners’ assumptions about each other’sknowledge (their partner models) on a subject are importantin spoken interaction. However, little is known about whatinfluences our partner models in spoken interactions withartificial partners. In our experiment we asked people to name15 British landmarks, and estimate their identifiability to aperson as well as an automated conversational agent of eitherBritish or American origin. Our results show that people’sassumptions about what an artificial partner knows are relatedto their estimates of what other people are likely to know -but they generally estimate artificial partners to have moreknowledge in the task than human partners. These findingsshed light on the way in which people build partner models ofartificial partners. Importantly, they suggest that people useassumptions about what other humans know as a heuristicwhen assessing an artificial partner’s knowledge.