The chapter I'm reading now is called "The Plastic Brain." It took me a moment to realize that Harkaway knows the original meaning of "plastic," before it was applied to mostly organic polymers with a distinctive texture and feel: it originally meant "moldable," and connoted substances that could be shaped and would hold the shape they'd been given. The thought passed through my mind that "plastic" might be a better adjective for human sexuality than the currently popular buzzword "fluid", except that I'm not sure most people would understand its being used that way.
Harkaway begins by pointing out that
Another example that I find suggestive is that bilingual people show up differently in brain scans depending on whether they acquired both languages before the age of four or five, or acquired the second one later in life. In the former case, both languages show up localized in the same area of the brain; in the latter, they are spread out to different areas. This sort of information is important, because I've run into people who've claimed that brain scans show different results in gay and straight people, which they assume to mean that the differences are at least inborn if not genetically determined; but such differences can be acquired as the result of learning.the brain is a versatile and even to some extent a volatile organ. It does, even in adulthood, alter its shape to take on new skills and abilities at the cost of others. The phenomenon is called 'neuroplasticity', and it is actually -- to a layman's eye -- remarkable. By way of example: the anterior hippocampus -- the region associated with spatial memory and navigation of a London taxi driver, seen in a magnetic resonance image, shows pronounced enlargement. Taxi drivers learn the streets and the flow of traffic, and that learning is reflected in the actual physical structure of their brains [81].
I can't help wondering what alternative there would be to the brain as a "genetically organized structure." Like many biological determinists, Pinker here overlooks the interaction between the genes and the environment that produces actual organisms. It's not a question of either / or. Does anybody argue that the brain isn't "genetically organized," at some level? At the same time, it's clear that "differences in intelligence, scientific genius [!], sexual orientation, and impulsive violence" are not entirely "organized" by the genes either.Having said that, it is important not to overstate the extent of neuroplasticity. Steven Pinker and Johnstone Professor of Psychology at Harvard, points out in The Blank Slate that 'most neuroscientists believe that these changes take place within a matrix of genetically organized structure.' However impressive the plasticity of the brain, there are limits. 'People born with variations on the typical plan have variations in the ways their minds work ... These gross features are almost certainly not sculpted by information coming in from the senses, which implies that differences in intelligence, scientific genius, sexual orientation, and impulsive violence are not entirely learned.' The question is how far the smaller changes within the brain can take one's identity before the brick wall of genetic structure is reached [82; emphasis added].
Analogously, the plastic arts use materials that can be shaped and manipulated -- clay, metal, wood, stone, concrete, and so on -- but there are physical limits to their plasticity, and artists who work with these media have to learn to respect them. There are people who talk, carelessly, as though organisms are infinitely malleable, and they're wrong. Nothing material has unlimited plasticity. But on the other side you have people like Richard Dawkins and his fantasy of organisms as "gigantic lumbering robots" in which hives of genes swarm. Dawkins tried to minimize this passage here, behind a flurry of rhetoric without a serious argument, especially since robots and computers were much less "intelligent" in the Seventies (when he wrote that passage) than he believes they are now. The real problem, though, is that he posits a sharp divide between the genes and the organisms they inhabit.
Ironically, it seems to be enthusiasts for genetic manipulation who believe that organisms are, or will be, infinitely malleable if we can just learn enough about the genome, and science enthusiasts generally who talk as though there were no limits to the plasticity of the human brain when it comes to the acquisition of scientific knowledge. The possibility that there might be some questions that can't be answered, not because there are things Man ought not to know, but because thought has limits imposed by the physical structure of the brain, tends to make them uncomfortable. I have no idea whether there are such limits, or what they might be if they exist, but I think it's a reasonable question.
