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 thoughtthat self-recognition was restricted to humans, great apes, and certain mammals with large brains andhighly evolved social cognition. However, 1 study showed that 2 out of 5 magpies (Pica pica) passed themark test, suggesting that magpies have a similar level of cognitive abilities to great apes. The scientificadvancement depends on confidence in published science, and this confidence can be reached only afterrigorous replication of published studies. Here, we present a close replication of the magpie study butusing 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 themirror versus a control cardboard stimulus. However, during the mark test, self-directed behavior provedmore frequent in front of the cardboard than in the mirror. Thus, our replication failed to confirm theprevious results. Close replications, while not disproving an earlier study, identify results that should beconsidered with caution. Therefore, more replication studies and additional experimental work is neededto unambiguously demonstrate that magpies are consistently able to pass the mark test. The existence ofcompelling evidence of self-recognition in other corvid species is discussed in depth.