The World in the Brain

I used to believe that we could understand psychology at different levels of analysis, and events at any one of the levels could be studied independently of events at the other levels. For example, one could study events at the level of the brain (and seek answers in terms of biological mechanisms), the level of the person (and seek answers in terms of the contents of thoughts, beliefs, knowledge, and so forth), or the level of the group (and seek answers in terms of social interactions). This approach seemed reasonable; the strategy of "divide and conquer" is a cornerstone in all of science, isn't it? In fact, virtually all introductory psychology textbooks are written as if events at the different levels are largely independent, with separate chapters (that only rarely include cross-references to each other) on the brain, perception, memory, personality, social psychology, and so on. 

I've changed my mind. I don't think it's possible to understand events at any one level of analysis without taking into account what occurs at other levels. In particular, I'm now convinced that at least some aspects of the structure and function of the brain can only be understood by situating the brain in a specific cultural context. I'm not simply saying that the brain has evolved to function in a specific type of environment (an idea that forms a mainstay of evolutionary psychology and some areas of computer vision, where statistics of the natural environment are used to guide processing). Rather, I'm saying that to understand how any specific brain functions, we need to understand how that person was raised, and currently functions, in the surrounding culture. 

Here's my line of reasoning. Let's begin with a fundamental fact: The genes, of which we have perhaps only some 30,000, cannot program us to function equally effectively in every possible environment. Hence, evolution has licensed the environment to set up and configure each individual's brain, so that it can work well in that context. For example, consider stereovision. We all know about stereo in audition; the sound from each of two loudspeakers has slightly different phases, so the listener's brain glues them together to provide the sense of an auditory panorama. Something similar is at work in vision. In stereovision, the slight disparity in the images that reach the two eyes are a cue for how far away objects are. If you're focused on an object directly in front of you, your eyes will converge slightly. Aside from the exact point of focus, the rest of the image will strike slightly different places on the two retinas (at the back of the eye, which converts light into neural impulses), and the brain uses the slight disparities to figure out how far away something is. 
            
There are two important points here. First, this stereo process — of computing depth on the basis of the disparities in where images strike the two retinas — depends on the distance between the eyes. And second, and this is absolutely critical, there's no way to know at the moment of conception how far apart a person's eyes are going to be, because that depends on bone growth — and bone growth depends partly on the mother's diet and partly on the infant's diet. 
            
So, given that bone growth depends partly on the environment, how could the genes set up stereovision circuits in the brain? What the genes did is really clever: Young children (peaking at about age 18 months) have more connections among neurons than do adults; in fact, until about eight years old, children have about twice as many neural connections as they do as adults. But only some of these connections provide useful information. For example, when the infant reaches, only the connections from some neurons will correctly guide reaching. The brain uses a process called pruning to get rid of the useless connections. The connections that turn out to work, with the distance between the eyes the infant happens to have, would not be the ones that would work if the mother did not have enough calcium, or the infant hadn't had enough of various dietary supplements. 
            
This is a really elegant solution to the problem that the genes can't know in advance how far apart the eyes will be. To cope with this problem, the genes overpopulate the brain, giving us options for different environments (where the distance between eyes and length of the arms are part of the brain's "environment," in this sense), and then the environment selects which connections are appropriate. In other words, the genes take advantage of the environment to configure the brain. 

This overpopulate-and-select mechanism is not limited to stereovision. In general, the environment sets up the brain (above and beyond any role it may have had in the evolution of the species), configuring it to work well in the world a person inhabits. And by environment I'm including everything outside the brain — including the social environment. For example, it's well known that children can learn multiple languages without an accent and with good grammar, if they are exposed to the language before puberty. But after puberty, it's very difficult to learn a second language so well. Similarly, when I first went to Japan, I was told not even to bother trying to bow, that there were something like a dozen different bows and I was always going to "bow with an accent" — and in my case the accent was so thick that it was impenetrable.  
            
The notion is that a variety of factors in our environment, including in our social environment, configure our brains. It's true for language, and I bet it's true for politeness as well as a raft of other kinds of phenomena. The genes result in a profusion of connections among neurons, which provide a playing field for the world to select and configure so that we fit the environment in which we inhabit. The world comes into our head, configuring us. The brain and its surrounding environment are not as separate as they might appear.  

This perspective leads me to wonder whether we can assume that the brains of people living in different cultures process information in precisely the same ways. Yes, people the world over have much in common (we are members of the same species, after all), but even small changes in the wiring may lead us to use the common machinery in different ways. If so, then people from different cultures may have unique perspectives on common problems, and be poised to make unique contributions toward solving such problems. 

Changing my mind about the relationship between events at different levels of analysis has led me to change fundamental beliefs. In particular, I now believe that understanding how the surrounding culture affects the brain may be of more than merely "academic interest."