Abstract
Self-determination theory presents a multi-dimensional approach to human motivation in which motivation is driven by a range of classifiably distinct regulation styles. However, these different regulations are also considered to fall along a continuum of self-determination which implies that a global dimension reflecting the degree of self-determination present is important. The lack of explicit integration between these two aspects in the conceptualization of motivation has recently led to debates and a flux of research on the structure of motivation as defined in self-determination theory. This review comprehensively explores recent advances in this area as well as more classical approaches in order to establish an optimal and empirically supported conceptualization of motivation. A novel solution is proposed, namely a semi-radex structure of motivation, in which types of motivation are predictably ordered by degree of self-determination while also maintaining their unique contribution as distinct factors. Theoretical and practical implications for researchers who use self-determination theory are made.