Two of three datasets from study where participants engaged in a spoken 'dialogue' with a pre-recorded video counsellor asking open questions to promote behaviour change. interview length and change talk results.csv reports duration of dialogue and number of instances of change talk and sustain talk detected by human coders in each participant's speech. Transcripts of participants' speech are not uploaded because we did not request participants' consent for sharing. When designing the study, we did not know if people would feel comfortable speaking aloud to the computer; we did not want to make them feel more self-conscious by knowing their speech would shared. The data are from 16 of 18 participants; two were excluded for not talking about a goal to increase physical activity, which was a requirement of the study. Version 1.0 contains ratings of the number of instances of change and sustain talk, which required the coder to judge when a complex statement should be scored as containing more than one instance. Version 2.0 was created in response to a reviewer's suggestion that coders should simply score the presence or absence of change and sustain talk. The new dataset presents the agreed scoring of two independent coders who scored whether change or sustain talk were present in each participant's response to each question posed by the video-counsellor. Questionnaire Units of Analysis.docx contains participants' written responses to an evaluation questionnaire completed one week after the interview. These responses were the raw material for thematic analysis. This dataset contains responses from 18 participants, including participants 7 and 11 who did not talk about a goal of physical activity when interacting with the video-counsellor.