In 2004 unexplained pedagogical barriers were limiting Learning Object (LO) development. Few reference points existed preventing the formation of specific pedagogical questions as to the nature of these barriers - hence this PhD's rationale. This thesis 'uncovers' the most effective pedagogical and evaluation/assessment* approaches for LO design in Medical Education, and the underlying principles within these approaches - i.e. what is effective, and why. To determine why certain approaches are effective observation/interview/usability studies were performed using grounded theory to generate hypotheses (1A Participants n=57). To verify 1A findings, this process was replicated using different sites/samples in Phase 2(Eastern/Midlands, n=72). To determine what was most effective, systematic reviews using a purpose-built design were undertaken with additional questions on pedagogy and evaluation/assessment• components (1B Studies n=222). Approaches identified as 'effective' according to statistics, SCIE and my own rigor scoring systems were tested blind in two locations (Eastern/Midlands) with different samples under a null hypothesis (i.e. 'Each approach will score no differently to any other', Phase 2 participants n=72). This was further developed by replicating this process via mobile delivery. Section 1A generated over a hundred hypotheses. In Section 1B, two existing approaches scored consistently high. Phase 2 produced the same hypotheses/approaches when submitted to the blinded observation/interview/usability process thus tight theme linkage resulted in rigorous theory and empirical data. The two top-performing 1B approaches scored high resulting in the possible existence of generic principles. When replicating 1A, 1B and Phase 2 for mobile delivery, the existence of generic principles was verified and a possible model for practice formed. In summary, this thesis underlines the importance of learner input and how learners' perceptions form an essential part of the LO learning process. It discovers original generic principles for both desktop and mobile formats, highlights how branch and loop learning systems are necessary for learner customisation, and provides new knowledge verifying Wiley's molecular LO analogy. *In this thesis many types of evaluation approaches are tested. These are called 'evaluation approaches' by the authors that created them. However, in some disciplines the term 'evaluation' is viewed as being interchangeable with the term 'assessment'. For this reason explanatory footnotes will be given throughout where necessary.EThOS - Electronic Theses Online ServiceGBUnited Kingdo