1) First, a pet peeve: just because something is can be localized in the brain using fMRI or similar techniques, does not mean it's innate. This drives me craaazy. Everything that we conceptualize or do is represented in the brain somehow (unless you're a dualist, and that has its own major logical flaws). For instance, trained musicians devote more of their auditory processing regions to listening to piano music, and have a larger auditory cortex and larger areas devoted toward motor control of the fingers used to play their instrument. [cite]. This is (naturally, reasonably) not interpreted as meaning that playing the violin is innate, but that the brain can "tune itself" as it learns. [These differences are linked to amount of musical training, and are larger the younger the training began, which all supports such an interpretation]. The point is, localization in the brain != innateness. Aarrgh.

2) The article talks about what agent-based modeling has shown us, which is interesting:

Using this technique, University of Michigan political scientist Robert Axelrod and his colleague Ross Hammond of the Brookings Institution in Washington, D.C., have studied how ethnocentric behavior may have evolved even in the absence of any initial bias or prejudice. To make the model as simple as possible, they made each agent one of four possible colors. None of the colors was given any positive or negative ranking with respect to the other colors; in the beginning, all colors were created equal. The agents were then provided with instructions (simple algorithms) as to possible ways to respond when encountering another agent. One algorithm specified whether or not the agent cooperated when meeting someone of its own color. The other algorithm specified whether or not the agent cooperated with agents of a different color.

The scientists defined an ethnocentric strategy as one in which an agent cooperated only with other agents of its own color, and not with agents of other colors. The other strategies were to cooperate with everyone, cooperate with no one and cooperate only with agents of a different color. Since only one of the four possible strategies is ethnocentric and all were equally likely, random interactions would result in a 25 percent rate of ethnocentric behavior. Yet their studies consistently demonstrated that greater than three-fourths of the agents eventually adopted an ethnocentric strategy. In short, although the agents weren't programmed to have any initial bias for or against any color, they gradually evolved an ethnocentric preference for one's own color at the expense of those of another color.

Axelrod and Hammond don't claim that their studies duplicate the real-world complexities of prejudice and discrimination. But it is hard to ignore that an initially meaningless trait morphed into a trigger for group bias. Contrary to how most of us see bigotry and prejudice as arising out of faulty education and early-childhood indoctrination, Axelrod's model doesn't begin with preconceived notions about the relative values of different colors, nor is it associated with any underlying negative emotional state such as envy, frustration or animosity. Detection of a difference, no matter how innocent, is enough to result in ethnocentric strategies.

As I understand it, the general reason these experiments work the way they do is that the other strategies do worse given the dynamics of the game (single-interaction Prisoner's Dilemma): (a) cooperating with everyone leaves one open to being "suckered" by more people; (b) cooperating with nobody leaves one open to being hurt disproportionately by never getting the benefits of cooperation; and (c) cooperating with different colors is less likely to lead to a stable state.

Why is this last observation -- the critical one -- true? Let's say we have a red, orange, and yellow agent sitting next to each other, and all of them decide to cooperate with a different color. This is good, and leads to an increased probability of all of them being able to reproduce, and the next generation has two red, two yellow, and two orange agents. Now the problem is apparent: each of the agents is now next to an agent (i.e., the other one of its own color) that it is not going to cooperate with, which will hurt its chances of being able to survive and reproduce. By contrast, subsequent generations of agents that favor their own color won't have this problem. And in fact, if you remove "local reproduction" -- if an agent's children aren't likely to end up next to it -- then you don't get the rise of ethnocentrism... but you don't get much cooperation, either. (Again, this is sensible: the key is for agents to be able to essentially adapt to local conditions in such a way that they can rely on the other agents close to them, and they can't do that if reproduction isn't local). I would imagine that if one's cooperation strategy didn't tend to resemble the cooperation strategy of one's parents, you wouldn't see either ethnocentrism (or much cooperation) either.

3) One thing the article didn't talk about, but I think is very important, is how much racial perception may have to do with our strategies of categorization in general. There's a rich literature studying categorization, and one of the basic findings is of boundary sharpening and within-category blurring. (Rob Goldstone has been doing lots of interesting work in this area, for instance). Boundary sharpening refers to the tendency, once you've categorized X and Y as different things, to exaggerate their differences: if the categories containing X and Y are defined by differences in size, you would perceive the size difference between X and Y to be greater than it actually is. Within-category blurring refers to the opposite effect: the tendency to minimize the differences of objects within the same category -- so you might see two X's as being closer in size than they really are. This is a sensible strategy, since the more you do so it, the better you'll be able to correctly categorize the boundary cases. However, it results in something that looks very much like stereotyping.

Research along these lines is just beginning, and it's too early to go from this observation to conclude that part of the reason for stereotyping is that it emerges from the way we categorize things, but I think it's a possibility. (There also might be an interaction with the cognitive capacity of the learning agent, or its preference for a "simpler" explanation -- the more the agent can't remember subtle distinctions, and the more the agent favors an underlying categorization with few groups or few subtleties between or within groups, the more these effects occur).

All of which doesn't mean, of course, that stereotyping or different in-group/out-group responses are justified or rational in today's situations and contexts. But figuring out why we think this way is a good way to start to understand how not to when we need to.

[*] Axelrod and Hammond's paper can be found here.