Mirror responses in African grey parrot (Psittacus erithacus) support the gradualist perspective on mirror self-recognition

Abstract

So far, only a handful of species have successfully passed the mirror test, showing the mirror self-recognition ability. Birds that have been claimed to show this ability are all corvids. In this study, we conducted a series of mirror-related tests, including open mirror exposure, mirror-mediated foraging task and mark test, to investigate this ability in the African grey parrot. Subjects responded to the mirror on three levels. Three subjects consistently showed social behaviours towards the mirror, two of which repeatedly hit the mirror throughout the test, indicating a complete lack of mirror perception and self-recognition. Two subjects showed social behaviours or hit the mirror almost within the first 10 min of the mirror trial, indicating they initially recognized mirror images as conspecifics but changed this misconception over time. There was only one individual, who not only never hit the mirror and exhibited social behaviours towards the mirror, but also could use the mirror to locate hidden food and mark on the body that was invisible without a mirror. However, considering the lack of contingent behaviours and spontaneous mirror-guided self-directed behaviours, it is hard to assert the African grey parrot possesses mirror self-recognition. All in all, we found our subjects responded differently towards the mirror, showing varying levels of understanding of the mirror. Our findings support the gradualist perspective on mirror self-recognition. Different mark methods are also discussed, and we suggest attaching the mark on the mandible in future parrot research.