The study of human-robot interaction commonly occurs in a laboratory environment in an endeavour to control the experimental conditions. Although convenient for the experimenters, a laboratory setting can constrain and therefore alter a participant's behaviour. In this paper we introduce the method of ‘open experimentation’ in which human-robot interaction studies take place outside the laboratory in a public social environment. Results from over 4,300 participants interacting with a humanoid robot, Diamandini, demonstrate that the general population preferred to observe the robot from a social distance, while children were comfortable to interact more closely with it and for extended periods of time.