When I began research with Alex, my first grant proposal was rejected not only with the flippant remark “What is this woman smoking?” but also with more serious criticisms, arguing that the studies I proposed were unlikely to succeed, given that birds lacked anything that looked like the primate cerebral cortex — the part of the brain in mammals that is responsible for intelligent behavior. Even after I started giving lectures in the 1980s with the data I had collected, my colleagues argued that no “mere bird” could possibly do what I was claiming.
Examining Bird Brains
Many of these naysayers, however, hadn’t done their homework. As far back as the beginning of the 20th century, researchers such as Kalischer (1901) suggested that for birds and mammals, different-looking brain areas might be responsible for the same types of intelligent behavior, and that just as for mammals, parallels could be made between the relative sizes of these areas and the extent of avian learning (see also Cobb, 1960; Portmann, 1950; Portmann & Stingelin, 1961; note Stettner, 1974; for a detailed review, see Pepperberg, 1999).
But it was not until the 21st century that the leading avian neurobiologists (Jarvis et al., 2005) published a paper clearly demonstrating that portions of the avian brain and the mammalian cerebral cortex actually functioned in the same ways, even though they looked completely different. [For those of you who want an example using specific neurobiological terms, the avian nidopallium caudolaterale (NCL) and the dorsolateral corticoid (CDL) areas, respectively, are likely homologues of the posterior parietal cortex and parts of the prefrontal cortex (Butler et al., 2005)]. Other research (Jarvis et al., 2013) clarifies additional correspondences between avian and mammalian brain areas.
Vocal Learning Differences In Birds
Of particular interest, however, are two very recent studies. One study, by Olkowicz et al. (2016), demonstrates that large-brained parrots such as Greys (as well as several corvids) have neuron counts in an area crucial for cognitive processing that are equal to or greater than primates with much larger overall brains; these authors suggest that the large numbers of neurons concentrated in high densities in this forebrain region are substantially responsible for advanced avian intelligence. The second study, by Chakraborty et al. (2015), examines brain structures involved in vocal learning.
Many avian species (sub-oscine birds such as North American flycatchers, members of the pigeon and chicken families) develop innately specified species-specific vocalizations, but are incapable of true vocal learning, and lack specific neural structures responsible for such learning. Vocal learning, and the requisite neural structures, characterizes the oscines, or songbirds (e.g., robins, wrens, warblers). Parrots also engage in vocal learning, and have a brain structure somewhat like that of songbirds. Unlike many (but not all) songbirds, however, parrots are open-ended vocal learners.
Consequently, unlike those songbirds that tend to learn the majority of their repertoire early in life (including aspects such as dialects common to the territories where they hatched) and make few, if any, changes in this repertoire over time, parrots are capable of learning new vocalizations throughout their lives.
The Brainpower Of African Greys And Similar Birds
Interestingly, Chakraborty et al. (2015) found that parrots such as the Grey have not only a neural system comparable to that of songbirds and hummingbirds for the learning of their species-specific vocalizations, but also a unique, separate “shell” system that may be responsible for their open-ended abilities to learn and acquire utterances of different species, including human speech. These authors also suggest that, because this shell system is larger in psittacine species like Greys that have shown advanced cognitive capacities, that this region may also be involved in nonvocal as well as vocal learning.
The moral of this story is that when anyone calls you a “bird brain,” take it as a compliment!
Butler, A.B., Manger, P.R., Lindahl, B.I.B., & Århem, P. (2005). Evolution of the neural basis of consciousness: A bird-mammal comparison. BioEssays, 27, 923-936.
Chakraborty, M., Walløe, S., Nedergaard, S., Fridel, E.E., et al., (2015). Core and shell song systems unique to the parrot brain. PLoS ONE 10(6): e0118496. doi:10.1371/ journal.pone.0118496
Cobb, S. (1960). Observations on the comparative anatomy of the avian brain. In D.I. Ingle & S.O. Waife, eds., Perspectives in Biology and Medicine, vol. 3. Chicago: University of Chicago Press, pp. 383-408.
Jarvis, E.D., Güntürkün, O., Bruce, L., Csillag, A., Karten, H., Kuenzel, W., Medina, L., et al. (2005). Avian brains and a new understanding of vertebrate evolution. Nature Reviews Neuroscience, 6, 151-159.
Jarvis, E.D., Yu, J., Rivas, M.V., Horita, H., Feenders, G., Whitney, O., Jarvis, S.C., Jarvis, E.R., et al. (2013). Global view of the functional molecular organization of the avian cerebrum: mirror images and functional columns. Journal of Comparative Neurology, 521, 3614–3665.
Kalischer, O. (1901). Weitere Mittheilung zur Grosshirnlocalisation bei den Vogeln (Further information on cerebral lesions in birds). Preussian Akademie der Wissenschaften, Berlin, 1, 428-439.
Pepperberg, I.M. (1999). The Alex Studies. Cambridge, MA: Harvard University Press.
Portmann, A. (1950). Système nerveux. In P.P. Grassé, ed., Traité de Zoologie, Paris: Masson, pp. 185-203.
Portmann, A., & Stingelin, W. (1961). The central nervous system. In A.J. Marshall, ed., Biology and Comparative Physiology of Birds, Vol. 2. New York: Academic Press, pp. 1-36.
Stettner, L.J. (1967). Brain lesions in birds: Effects on discrimination acquisition and reversal. Science, 155, 1689-1692.
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