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August 20, 2008

Welcome to the club, Magpie (Pica pica)

The past 20 years have already been a humbling experience for people sympathetic to the idea that humans are unique among animals. For many years, it was thought that tool use was an exclusive trait of humans, but then the evidence rolled in that other primates routinely use tools. The real shocker, of course, is that some birds also use tools [1]. And so it also went for cultural knowledge , long-term planning behavior, creativity, and dreaming. All of these behaviors are seen not just in other mammals, but in some species of birds. All this evidence makes it increasingly difficult to argue that there is much fundamentally special about Homo sapiens, except perhaps the coincidence of all of these behaviors in a single species.

To this list of human-like behaviors that birds exhibit, it seems we can now add self-recognition, at least for the European Magpie (Pica pica) [2]. This idea is usually illustrated by the so-called mirror test [3]: some kind of mark is placed on an animal in a spot they cannot normally see (on their chin, forehead, etc.), and a mirror is then placed so that they can see the mark on themselves. The usual interpretation of the resulting behavior is that if the animal recognizes themselves in the mirror, they will scratch directly at the foreign mark that they cannot normally see [4]. This kind of mirror use is seen in all the great apes (humans older than 18 months, bonobos, chimpanzees, organutans and gorillas), dolphins, killer whales and elephants.

Of course, we still have no explanation of what allows such mirror-recognition to happen. Is it the size of the brain alone? (Probably not, but size is likely important in some ways.) Is there some special structure in the brain that mediates it? (Maybe. It would be interesting to stick some of these animals into a CT scanner while they're doing this test to see if there are homologous regions of the brain that light up.) Etc. One thing that's interesting about this new discovery of self-recognition in Magpies is that these birds are in the corvid family, which includes other clever birds like crows. This group of birds are fairly large, and thus have relatively large brains, so it may be that whatever neurological structures facilitate self-recognition, they require relatively large masses of neurons. From a more general perspective though, it's exciting that all of these "complex" behaviors appear in birds. Because their brains are structured quite differently from mammal brains, it suggests that there's not one single way to create "intelligent" brains. If it turns out that there are many many ways to create complex behavior, then perhaps one day we'll figure out what the essential structures and dynamics are, and be able to build one from scratch.


[1] This is pretty clearly a case of convergent evolution, since surely not all of the interceding species between birds and mammals were also tool users.

[2] H. Prior, A. Schwarz and O. Güntürkün, "Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self Recognition." PLoS Biology 6, e202 (2008).

[3] The mirror test has, in fact, been heavily criticized for its indirectness and its bias toward human-style self-recognition. Of course, as anyone who's encountered the mind-numbing stupidity of corporate customer service, it can be extremely difficult to judge from behavior alone whether an animal is actually a thinking being. Examples abound of humans fooling ourselves and each other on this issue. If you ever want to experience this difficulty first-hand, try discussing with someone else whether your subjective experience of the world is similar or different from theirs.

[4] The control for this kind of experiment is to use two different color marks, one that is flesh- (or feather-)colored and one that is not.

posted August 20, 2008 07:56 AM in Obsession with birds | permalink