— As an increasing number of robots have been designed to interact with people on a regular basis, research into human-robot interaction has become more widespread. At the same time, little work has been done on the problem of long-term human-robot interaction, in which a human uses a robot for a period of weeks or months. As the person spends more and more time interacting with the robot, it is expected that the means by which they make sense of the robot and its behavior - their “cognitive model” of the robot - may change over time. In order to examine this cognitive model, a study was conducted involving the Personal Exploration Rover (PER) museum exhibit and the museum employees responsible for them. The results of the study suggest a number of relevant components of a cognitive model for human-robot interaction which will be further examined in an upcoming study on scientist-rover interaction.