Research paper
Credé M, Tynan MC, Harms PD. Much ado about grit: A meta-analytic synthesis of the grit literature. Journal of Personality and Social Psychology. 2017 Sep;113(3):492–511. doi:10.1037/pspp0000102. Epub 2016 Jun 16.
Why we cite it
Supplies the corpus's only counterweight to `cgr01`, which until now was the sole substantive source on grit in a library where six companions lean on it. Before this citation, a piece drawing on grit would have presented one side of a live scientific argument as settled.
Its more useful contribution is finer than "grit is contested." The meta-analysis **splits the construct**: perseverance of effort holds up considerably better than consistency of interest, and perseverance predicts academic performance even after conscientiousness is controlled for. So the corpus does not have to choose between endorsing grit and discarding it. It can say the durable half is sustained effort, and that the "passion"/consistency-of-interest half — which is the distinctive part of Duckworth's definition — is the part the aggregate evidence supports least.