by Rong Bi, Jan Grohn, Patricia L. Lockwood, Miriam C. Klein-Flügge, Lilian Weber Humans show remarkable flexibility in adapting their behaviour to constantly changing environments. This flexibility relies on the ability to regulate motivation in response to changing motivational demands. Typically, the amount of effort required to achieve a certain goal is not precisely signalled by the environment but needs to be learnt from experience. By contrast, prior work examining motivated choices has usually directly instructed effort requirements. It therefore remains unclear how healthy individuals estimate and flexibly regulate effort and how they might achieve this in dynamically changing environments. In the current study, we examine how effort learning is shaped by different types of environmental uncertainty when motivational requirements are not explicitly instructed. Analogous to tasks in the reward learning domain, we designed a novel effort learning task that systematically manipul