Replication of the Mirror Mark Test Experiment in the Magpie (Pica pica) Does Not Provide Evidence of Self-Recognition

Self-recognition in animals is demonstrated when individuals pass the mark test. Formerly, it was thought that self-recognition was restricted to humans, great apes, and certain mammals with large brains and highly evolved social cognition. However, 1 study showed that 2 out of 5 magpies (Pica pica) passed the mark test, suggesting that magpies have a similar level of cognitive abilities to great apes. The scientific advancement depends on confidence in published science, and this confidence can be reached only after rigorous replication of published studies. Here, we present a close replication of the magpie study but using a larger sample size while following a very similar experimental protocol. Like the previous study, in our experiment, magpies showed both social and self-directed behavior more frequently in front of the mirror versus a control cardboard stimulus. However, during the mark test, self-directed behavior proved more frequent in front of the cardboard than in the mirror. Thus, our replication failed to confirm the previous results. Close replications, while not disproving an earlier study, identify results that should be considered with caution. Therefore, more replication studies and additional experimental work is needed to unambiguously demonstrate that magpies are consistently able to pass the mark test. The existence of compelling evidence of self-recognition in other corvid species is discussed in depth.