I have completely forgotten this person’s name, but I am going to call her Crystal Powers, because she so completely embodied a California archetype of the unmoored spiritualist. We were at a party after an art opening and she had asked about my job. At the time I was a graduate student, working on a project with zebra finches. The study was about how it is that they acquire songs early in development, and then continue to sing these same songs throughout their lives, without much change. It is a classic “sensitive period” phenomenon, and understanding how it’s regulated might provide clues about sensitive periods for language, which is what I was really interested in, and which, amazingly, is something I am still working on.
At the time there was a good deal of excitement about zebra finch song learning, because it was becoming clear that the situation was much more complicated than people had previously thought. The tidy explanation that had held sway for a long time was that this sensitive period was genetically programmed. Evidence for this came from studies in which the gross size of parts of the bird’s brain that are critical for song learning changes dramatically over time, so that they are at their largest when song is typically learned, and then shrink down to a fraction of the size just before adulthood, when the sensitive period closes. Other markers of the ability to learn, or plasticity changed in a similar way that appeared neatly timed to the behavioral sensitive period.
Recent work, had shown, however, that those anatomical and physiological changes could, to some degree, be uncoupled from behavioral change. For example, birds raised without exposure to song will lose particular markers of plasticity at the anatomical and cellular level more slowly than birds raised hearing song. That by itself is sort of amazing to contemplate. We’re not talking about entirely removing auditory input — the “isolate” birds are often raised by females, who even produce a range of species-specific vocalizations, just not song.
Nonetheless, birds isolated from song eventually do undergo many of the changes associated with the sensitive period, if on a somewhat delayed schedule. Their brains grow, and then shrink. Their NMDA receptors convert from juvenile to adult form. Their cell physiology takes on adult-like features. The puzzle was that these isolate birds with their adult-like brains were still capable of substantial learning. They were not as good as juveniles, but they were able to learn new songs from other adult birds, which is not something adults normally do. This meant that the maturation of physiological properties of the song system couldn’t be sufficient for closure of the sensitive period. This fit in nicely with data from many different model systems, suggesting that plasticity can be restored in adulthood under a wide range of conditions, even in systems thought to be “locked down” by the closure of sensitive periods. It was an exciting and productive time, even if, in retrospect, we may have gone overboard in claiming that the brain was always and everywhere changeable by experience.
I was somewhere very early in the process of explaining all of this when Crystal cut me off:
“What if it’s just their way?”
“What if they stop learning in adulthood because that’s just their way?”
I don’t remember what I said next, but I do know that at some point I started yelling, or doing what counts as yelling in California (it’s different in New York, where I’m from).
“It’s their way” is a marginally acceptable answer to an inquisitive three year old whom you suspect to be intentionally trying to forestall bath time by asking questions. It’s not an explanation, it is “a makeshift, an admission of helplessness before the problem of reality.”
I’m pretty sure I tried politely to explain that the goal of researching this question is to figure out what it means for this to be “their way.” What parts of this system are under such strong genetic control that they turn out more or less the same whatever the developmental milieu is like? And what parts are so exquisitely tuned to experience that they can be modified on the fly over the entire lifespan? And what about all of the stuff in between — which is about 99% of biology — the stuff that depends in part on genetic inheritance, in part on experience and part on dumb luck? What is the nature of “their way?”
I’m still not sure what was going on there. Maybe Crystal Powers was baiting me. In my memory she has fused with the woman in a Range Rover from whom I snaked a parking spot in front of the Bodhi Tree bookstore in West Hollywood. When I came back from lunch I found a note on my windshield that said “Your kindness on this day will be remembered.” This was probably one of my first encounters with the judgmental, passive-aggressive underbelly of the otherwise wifty and sweet New Age subculture, and our argument about The Way of the Zebra Finch was giving me the same drained, heavy feeling emanating in both directions from about the third chakra.
And yet, I have actually became somewhat sympathetic to this viewpoint over time. Not, of course, that a scientific explanation can stop at “it’s their way,” but that there is something missing from the laboratory study of animals outside a more holistic context. What if, in the search for things to catalog, quantify and manipulate, we’ve reduced the bird’s world to something totally outside what its genetic inheritance has prepared it for?
There is a continuum in animal research from something like Jane Goodall’s observations of primates in Gombe, to advanced techniques in molecular biological research that treat the life of the subject mostly as the medium necessary to cultivate the proteins they’re interested in. Both are important, but both also are limited in important ways. It can be easy, when dazzled by the technological sophistication of a modern lab, to lose sight of the fact that it is missing something — something that potentially could only be gained by sitting in the jungle, and watching.
There is a whole range of interesting behaviors that occur in the middle zone between these extremes, and there used to be a thriving field of neuroethology dedicated to tracking down the neural basis of these behaviors. Some branches of this field survive, but the golden age had already passed when I discovered it. In fact it was in free fall, and without intervention soon might go extinct. Niche behaviors like sound localization in owls, echolocation in bats, or sexual promiscuity in voles are hard to directly relate to disorders, and as a result, funding for neuroethology has been cut mercilessly over the last two decades. Money has been redirected instead toward projects that can help characterize disorders, identify drug targets, or otherwise lead to monetizeable deliverables, rather than basic, curiosity-driven research. This is sad, because it means that we are unlikely to learn anything new about the biology underlying a wide range of complex behaviors. It’s also short-sighted, because we really don’t know where the next breakthrough will come from. Many of today’s hot topics in treatment and drug discovery are based on research that started with basic questions about things like the mysterious “way of the zebra finch.”
illustration by Leah Beeferman