“A replication attempt with a sample from a more diverse population, over 10 times larger than the original study, showed only half the effect of the original study. The replication suggested that economic background, rather than willpower, explained the other half.[6][7] The predictive power of the marshmallow test was challenged in a 2020 study.[8][9] Work done in 2018 and 2024 found that the Marshmallow Test "does not reliably predict adult functioning".