“…The finding that scores on low-stakes tests do not always reflect students' true ability has already been recognized in the literature (Wise and DeMars 2005 and Finn 2015 provide reviews). One strand of research uses observational data to examine correlations between performance and proxies for motivation and effort, including self-reported motivation, interest, attitudes and effort, fast response times, low item response rates, and declining performance over the course of the test (e.g., Eklöf 2010; DeMars and Wise 2010; Borghans and Schils 2013; Zamarro, Hitt, and Mendez 2016;Borgonovi and Biecek 2016;Balart, Oosterveen, and Webbink 2017;Akyol, Krishna, and Wang 2018). 3 Yet, important for our purposes, these studies are not able to identify the impact of effort separately from the impact of ability.…”