Abstract: A computer system is described for providing intervention suggestion information to a user, for the purpose of changing a psychological state of the user. The information suggestion information identifies at least one recommended intervention, selected from a pool of candidate interventions. Each candidate intervention, in turn, involves a type of computer-related activity with which the user is likely already familiar. The computer system formulates the intervention suggestion information in the form of one or more messages, delivered to one or more user devices, such as a mobile user device, or a mobile user device in conjunction with an ambient presentation device. According to one optional aspect, the computer system chooses the recommended interventions based on context information. According to another aspect, the computer system selects interventions by adopting a particular balance between an exploitation mode and an exploration mode.