Towards clear construct definitions: Applying an iterative approach to constructs of the Health Action Process Approach (HAPA).

The psychological and behavioural sciences have long struggled with issues of replicability and reproducibility, often attributed to poorly defined psychological constructs. Clear and precise construct definitions are essential for advancing theory development, improving measurement validity, and fostering scientific communication. This study aimed to develop comprehensive definitions for key constructs within the Health Action Process Approach (HAPA), a widely used model in health psychology. Using a structured, iterative methodology adapted from Podsakoff et al. (2016), we focused on refining definitions for action planning, coping planning, self-efficacy, and action control—core constructs in the model’s post-motivational phase. The resulting definitions are intended for inclusion in the Decentralised Construct Taxonomy (DCT), promoting transparency and consistency in construct usage. This work offers a replicable framework for construct definition development, with implications extending beyond the HAPA model to the broader behavioural sciences.