“Interest” is a key concept in the field of science education and engagement. Science centres, museum exhibitions, programmes and interventions are designed to stimulate the interest of visitors. But what exactly is interest and how does it relate to curiosity? What makes something interesting? Are there different types of interest? What factors breed curiosity? And how do we measure these factors? Interest as a concept is ill defined. All too often it’s meaning is taken for granted and based on intuitive assumptions. Furthermore, interest has often been conflated with the notion of curiosity – although the two are not always the same.This poses problems not only for programme development but also for evaluation, as interest has been shown to come in a variety of different flavours and stages of development. This session aims to unpack the notions of interest and curiosity, applying insights and understandings from the field of psychology, in addition to findings from new research into STEM engagement. The presentations will challenge and redefine participants’ understanding of these concepts, aiding development and evaluation of STEM programmes focused on these concepts in the future.