A research project (whose objectives and methods have recently been published in the Annals of Behavioral Medicine) led by Dr. Susan Michie (University College London, UK) aims to develop matrices of hypothesised links between behaviour change techniques (BTCs) and specific mechanisms of action as well as behavioural theories. Linking BCTs to the mechanisms of action described in behavioural theories allows researchers to target mechanisms of action more deliberatively and makes it easier for investigators to design studies that can evaluate the processes underlying effective interventions.