Health is important, but the health of the nation is failing, with chronic diseases, such as cardiovascular disease, cancer and diabetes on the rise. Most of which are related to the performance of negative health behaviours. As a result, improving the health of the population through the promotion of positive health behaviours is a key aim of health professionals and Government. However, to promote positive health behaviours, first, what variables predict health behaviour must be identified. Two prominent variables of interest are cognition and personality. Recently, attention has focussed on executive control (EC) and conscientiousness as predictors of health behaviour. As such, a number of questions have emerged. Firstly, due to the conceptual overlap of these variables, are they related constructs? Secondly, do they have a direct impact on health behaviour? Finally, are they moderating variables, and do they moderate the intention-behaviour relationship? The aim of this PhD was to explore the relations between EC, conscientiousness and multiple health behaviours in healthy samples. Over four studies, participants completed an array of computer, and paper and pencil-based tasks and computer-administered questionnaires. In addition, behavioural intentions and health behaviour performance was measured over a period of 7-14 days using online daily diaries. Using multilevel modelling analysis, three main findings emerged. First, the relationship between EC and conscientiousness is dependent on the measures used. Second, some EC and conscientiousness measures have direct effects on health behaviour; and third, some EC and conscientiousness measures have indirect effects on health behaviour via moderation of the intention-behaviour relationship. The findings highlight EC and conscientiousness are significantly related to health behaviour performance, though the relationships are more complex than shown by previous research. As such, the current findings serve to highlight issues of construct complexity, ecological validity, sample diversity and measurement
