The empirical investigation of free will beliefs is a fascinating and extensive field, offering potential insights into the extent and ramifications of free will beliefs, but this research is not without its limitations. Many competing definitions of free will exist. These competing definitions have informed the variety of free will manipulations and measures currently used, often without researchers properly addressing the important differences in the understandings of free will being operationalised, manipulated and measured. These manipulations and measures are also typically (...) broad ranging, also including statements targeting determinism, reductionism and other related constructs. They therefore lack the focus necessary to identify just what aspect of these supposed free will manipulations are actually impacting cognitions, beliefs, and behaviours. Across 7 studies we address some of these limitations. Study 1 confirms past findings demonstrating that perceptions of having choice and being free from constraints are central to lay understandings of free will. Study 1 also tests new single item measures of free will and determinism. In studies 2 and 3 we use our new measure of lay free will, to demonstrate that the previously established utility of free will beliefs for predicting subjective wellbeing, is due to the perceptions of having control that form the core of lay free will beliefs. We then reason that, as pro deterministic/anti free will messages can undermine free will beliefs these manipulations may also impact perceived control and subsequently indicators of subjective wellbeing. Studies 4 and 5 demonstrate that an abridged version of the Crick essay, can undermine perceived control. This suggests that past successful manipulations of behaviour via the Crick essay, may have been due, at least in part, to reductions in perceived control rather than just free will beliefs. The Crick essay is a broad ranging, poorly focused manipulation, simultaneously championing determinism while undermining the idea of free will. We therefore then endeavour to create two new, better focused, manipulations of free will/determinism, with reduced demand characteristics. In study 6 our TMS manipulation lead to a significant reduction between participants’ pre and post manipulation scores but this was also true for participants in the neutral condition. These complex findings are explored, suggesting that placing participants in an intimidating environment may undermine their perceptions of having free will. In study 7 our deterministic video manipulation successfully undermines free will belief but does not undermine perceived control or self-efficacy. These findings are explored further with participants’ agreement with the deterministic or non-deterministic video lecture, moderating the impact of condition on participants’ ratings of free will, self-efficacy and perceived control. When compared to non-determinism, high agreement with determinism was associated with lower perceived control and free will belief. By contrast low agreement with determinism was associated with higher perceived control self-efficacy and free will. In study 1 we created a new measure of cheating/dishonesty that can be used online. In study 7 we used this new measure of cheating and contrary to our predictions, exposure to a deterministic argument led to less cheating than exposure to a non-deterministic argument. In the general discussion the various strands of research are brought together and their contribution to the literature discussed. The limitations of our research are explored with new ideas proposed to address those limitations and further our work. Taken together, the research outlined in this thesis provides valuable new insight into the nature and implications of beliefs relating to free will and determinism, provides a valuable critique of research in this field and offers suggestions to improve and extend the current literature. (shrink)