Comments on "Intra- and interspecific variation in self-control capacities of parrots in a delay of gratification task".

Brucks (Anim Cogn 25(2):473-491, 2021) have published an intriguing paper on the differing abilities of various species of parrots to succeed in a delay of gratification task. I find their interspecies comparisons of considerable interest but take exception to their misrepresentation of prior research on delayed gratification from our laboratory in Koepke (J Comp Psychol 129:339-346, 2015). Contrary to their claims, our subject was never trained on the task; rather, one might argue instead that all their subjects received considerable training or at least forms of pre-exposure that could affect their overall claims. I also briefly discuss other design features that may have affected their results.