Considering an interactive computer as a social stimulus suggests that contemporary social psychological theories can contribute to the prediction of user attitude and performance. In order to assist in the systematic exploration of this possibility, we developed DIALOGUE, an on-line system to investigate the effects of varying the computer's responses to the user. This system involves a presentation program that displays the computer's responses, performs the pacing of video information, and collects a variety of measurements, including the user's response time and the number of correct/incorrect user responses. DIALOGUE also includes a data manager that allows the experimenter to examine or modify the information collected by the presentation program. Utilizing DIALOGUE, we conducted a preliminary investigation of one aspect of human-computer interaction, the effects of varying the degree of human-like responses exhibited by the computer. Results suggest that (1) there are underlying dimensions of judgment involving perception of interactive computers, (2) a manipulation of human-like computer responses is reflected primarily in certain of these dimensions, and (3) such a manipulation influences user performance and feelings of responsibility. Factors related to the implementation of DIALOGUE are considered, and its potential for investigations of a variety of human-computer interactions is discussed.