Relational reasoning – responding to one stimulus is terms of another – is central to human cognition. Relational reasoning involves (1) the detection and combination of information, and (2) the deployment of relational information to transform the functions (e.g., motivating, discriminative, or reinforcing) of the stimuli being related. Unfortunately, due to a lack of appropriate measures relational reasoning research has neglected the ability for transforming stimulus functions. This project aims to address this issue by creating a battery of function transformation tasks that directly target the ability to transform stimulus functions. Work package 1 will create a psychometrically sound function transformation task test battery. Work package 2 will investigate how the ability for transforming stimulus functions relates to the ability for detecting and combining relational information. Work package 3 will investigate whether the ability for transforming functions can be trained. Work package 4 will assess whether training the ability for transforming functions boosts relational reasoning interventions. The overarching aim of this project is to kick-start research on transforming stimulus functions. Successfully delivering the four work packages will equip researchers with the necessary tools for a more complete science of relational reasoning, will advance that basic science, and will set the stage for advances in applied efforts to improve relational reasoning abilities.