In this project we focus on understanding the impact of mobile behaviour change support systems in terms of two psychological constructs that are widely acknowledged to play an essential part in the initial, as well as the long-term, engagement with behaviour change support systems, i.e., trust calibration and intrinsic motivation.

One of the key determinants of user acceptance of any automated system is the extent to which a user trusts the system. Appropriate trust calibration, such that the perceived trustworthiness of a system matches its actual trustworthiness, is a critical factor for achieving the full potential of behaviour change support systems. In cases of mistrust, users may discard the system’s feedback or advice, thus not benefitting from potentially important health interventions. On the other hand, in cases of overtrust, the user may overly rely on the system, transferring control without an appropriate level of insight into the rationale of the advice, its limitations, or potential ill effects. Especially for systems that are less than 100% reliable, it is of critical importance to aid users in building an accurate mental model of the system’s decision making process and capability. This will also help to avoid inflated expectations, and subsequent disappointment and discontinued use of the behaviour change support systems – which currently presents a substantial issue (Clawson et al., 2015; Cordeiro et al., 2015).

A second key concern in the success of behaviour change support systems is the extent to which these technologies enable or support intrinsically motivated behaviours. Intrinsic motivation refers to behaviours that inherently provide enjoyment or satisfaction, and they are typically distinguished from externally motivated behaviours, which refer to behaviours that bring a desirable, separable outcome (Ryan & Deci, 2000a). Intrinsic motivation is regarded as the most powerful form of motivation and an impressive body of research has demonstrated the relation of intrinsic motivation with behavioural persistence and performance in various health-related behaviours as well as professional behaviours (e.g., Ryan & Deci, 2000). Extrinsically motivated behaviours are often not sustained and are experienced as less satisfying. Self Determination Theory (SDT) prescribes that whether a behaviour is intrinsically or extrinsically motivated or not motivated at all, is influenced by the extent to which the behaviour satisfies three psychological needs: the need for autonomy, the need for competence and the need for relatedness. How mobile BCSS affect these psychological needs requires further research.