Abstract: Among other things, a computer-implemented method includes, on successive occasions over a period of time, gathering measured data and self-reported data that represent health states of participants in a health goal system, based on at least some of the gathered data, determining, by machine learning, data representing a relationship between sequences of self-applied interventions and health states of participants who belong to respective groups that share similar characteristics, calculating scores representing characteristics of interactions between participants and the health goal system, and based on the scores and the data determined by machine learning, choosing elements of conversations to be provided to the participants, elements of the conversations being chosen to affect (i) behaviors, (ii) health states, or (iii) health awareness, or a combination of any two or more of them, of the participants, the elements of the conversations comprising questions posed to the participants on user interfaces of e