Self-generated validity (SGV) describes the finding that asking participants to report their intention to perform a behaviour (eg, "Do you intend to donate blood?") causes greater subsequent performance of that behaviour compared to not asking about intentions. Our recent research has shown that SGV can be used to increase two objectively assessed health behaviours (blood donation; screening attendance) over periods of up to 12 months. We aim to further our understanding of SGV and assess how it can be used to promote behaviour change. We will explore the generality of SGV (across approach and avoidance behaviours; and across different cognition measures), the mechanisms of effect (role of degree of deliberation about the behaviour and public commitment to the behaviour), and the moderators of the effect (impact of measuring different cognitions, impact of different levels of past experience with the behaviour). Real world Randomised Controlled Trials on two behaviours (cervical screening, child immunisation) will examine what factors influence SGV. In addition, Laboratory Experiments will further elucidate the generality, mechanisms and moderators of SGV. Better understanding of SGV would inform its use as a simple but effective way to change behaviour and inform our understanding of how merely measuring cognitions may change behaviour.