Can grey parrots (Psittacus erithacus) succeed on a "complex" foraging task failed by nonhuman primates (Pan troglodytes, Pongo abelii, Sapajus apella) but solved by wrasse fish (Labroides dimidiatus)?

Linking specific cognitive abilities of nonhuman species on a laboratory task to their evolutionary history-ecological niche can be a fruitful exercise in comparative psychology. Crucial issues, however, are the choice of task, the specific conditions of the task, and possibly the subjects' understanding or interpretation of the task. Salwiczek et al. (2012) compared cleaner wrasse fish (Labroides dimidaitus) to several nonhuman primate species (capuchins, Sapajus paella; chimpanzees, Pan troglodytes; orangutans, Pongo abelii) on a task purportedly related to the ecological demands of the fish, but not necessarily of the nonhuman primates; fish succeeded whereas almost all of the nonhuman primates that were tested failed. We replicated the two-choice paradigm of the task with three Grey parrots (Psittacus erithacus), whose ecology, evolutionary history, and cortical capacity are arguably more like those of nonhuman primates than fish. Greys succeeded at levels more like fish than all the nonhuman primates, suggesting possible alternative explanations for their success. Fish and nonhuman primate subjects also experienced a reversal of the initial conditions to test for generalization: Greys were similarly tested; they performed more like fish and capuchins (who now succeeded) than the apes (who continued to fail).