How rational is the human brain?
Photo courtesy ofL By Amber Rieder, Jenna Traynor, Geoffrey B Hall (Own work) [CC0], via Wikimedia Commons MRI_Location_Amygdala_up
JDN 2457111 EDT 11:19.
[I like to use the Julian Date Number system for keeping track of dates because is secular (not tied to any particular religion, unlike BC/AD), uses a single unit of measure (days) instead of several (days, months, years), is already in widespread use in astronomy—and also sounds a lot like a Stardate.]
As I like to say, humans are 90% rational—but woe betide that other 10%.
Are humans completely rational? Do we behave as rational agents who maximize expected utility?
It should be obvious that the answer is no—people often do, say, and believe remarkably irrational things, and if they didn't we wouldn't have much need for an "idiot free zone". If we were completely rational, everyone would believe in global warming, no one would believe in religion, and there could absolutely never have been anything remotely like Daesh.
Maybe we could still have certain kinds of conflicts or macroeconomic instabilities, though even then it seems to me that if we were really so smart we'd come up with policies to resolve our conflicts and maintain stability. At the very least, perfectly rational beings with perfect information should attain Pareto-efficiency, a state in which no one could benefit without someone else being harmed. I'm not just asserting that, you can prove it. And I do mean prove in the strongest sense of the word: formalized with certain assumptions it is a mathematical theorem, the First Fundamental Welfare Theorem. Yet plainly this is not how the world works; even though Pareto-efficiency is overrated (a world in which one person owns literally everything is Pareto-efficient), we clearly don't even have it; by ending war, genocide, slavery, and racism, millions of lives could be improved without harming anyone else. I could go on, but most of you already agree that humans are not completely rational.
Yet most economic models in wide use—"neoclassical" models as they are generally known—assume this extremely strong notion of human rationality, and even take it a step further by equating rationality with selfishness. Many economists honestly seem baffled by the idea that it could ever be rational to help someone else with no expectation of return; my favorite was when an economist put 'altruism' in scare quotes. Economic policy has been designed accordingly, and with this is mind, is it really so surprising that corporations grow ever-more powerful and ever-more corrupt and business executives are about 4 times more likely than the general population to be psychopaths?
On the other hand, we shouldn't let ourselves go too far in the opposite direction and conclude that human beings are totally and irredeemably irrational. If we were fully rational, Idiot Free Zone would be unnecessary; if we were fully irrational, it would be impossible. Indeed, civilization itself would be impossible; if we were simply gorillas in cheap tuxedos we would behave the way that gorillas behave when you put them in cheap tuxedos.
In fact, even gorillas are quite intelligent; gorillas are capable of making and using tools, for example, as well as recognizing themselves in the mirror. So let's consider something obviously far less intelligent: an ant. Are even ants really totally irrational?
No, they aren't; while ants cannot write novels or even make tools, and they do not exhibit the emotional complexity of dogs, the problem-solving ability of crows, or the cleverness of octopus, nonetheless ants can, under the proper conditions, locate food, evade predators, and provide for their queen to ensure their own progeny.
A totally irrational being is one that would immediately destroy itself; there are simply too many more ways to be dead than to be alive. Indeed, the very notion is almost incoherent, as such a creature could never evolve in the first place; it would have to be specifically designed by a pre-existing rational being, perhaps as an existentialist art project in order to demonstrate its very futility. (Actually now that I say that, I have little doubt that in the transhuman future there will be individuals interested in such projects, and we will need strict regulations on the sentience of art-project AIs.)
Hence, human beings are actually quite rational; if you compare us on the one hand to a completely irrational being that immediately destroys itself and on the other hand to a completely rational being that lives its entire existence in the perfection of its desires, we are in fact closer to the latter end. Over the centuries our rationality has improved as we have discovered new knowledge, restructured our social institutions, invented new technologies, and improved our health and education.
Even most of our irrational behaviors are almost rational, in the sense that they were rational when we evolved them millennia ago, or in the sense that they would advance our goals except for some piece of information we're missing or some false belief we have.
Let's talk about Daesh, for example; they may seem like the pinnacle of human irrationality, and in a sense they are. A young man who travels halfway around the world in order to blow himself up along with a building full of people for believing in a subtly different interpretation of a 7th century book is clearly not behaving with optimal rationality. And yet, as unwilling as most of our society is to recognize this fact, his actions are comprehensible—they are not simply incoherent madness, and they are by no means unpredictable. (Maybe the individual targets are unpredictable, but even this is entirely rational; it is a mixed strategy. Against a superior opponent, guerilla warfare targets unpredictably to avoid defenses that would be otherwise overwhelming.) Given only one false premise, the argument for his actions is valid; given that assumption, his behavior is entirely rational. That premise? That these actions please Allah, who will reward him eternally with maximal happiness in Heaven. Given the prospect of an eternal reward, particularly one of maximal happiness, it would be entirely rational to do almost anything to achieve that reward. The only cost that would not be worth paying would be sending others to eternal punishment or denying them eternal happiness. If Heaven exists, baptizing babies and then killing them (as Conquistadors did) is a deeply altruistic act; even if it dooms you to Hell at least it sends those babies to Heaven. This woman who shot her own child is making a perfectly valid argument; her only delusion is believing in Heaven and Hell—actually believing in them, the way that I believe in chocolate and cyanide, as things that actually exist in the world. When most people say that they "believe in Heaven", they are lying (at least to us, if also to themselves); if they actually believed they would act like people in Daesh, or else they would follow Matthew's beattitudes to the letter and donate all their possessions and mutilate themselves as punishment for feeling angry or tempted. They would be willing to commit torture and murder if they thought it would convert people to the true religion, because any finite period of suffering cannot possibly be as bad as an infinite period of maximal suffering. Combine that with our deep-seated instincts for tribal identity, evolved over millennia in which tribal identity was life itself (also the basis of racism and nationalism), and you have a very dangerous combination—from a brain that is overall being almost entirely rational. Fanatical religion is not dangerous because it is so irrational; on the contrary it is dangerous because it is so rational, given only that you actually believe the premises that religion entails. It is dangerous precisely because it can drive human beings who are otherwise intelligent and reasonable to horrific violence.
Nor is it inherently irrational that we are so driven by emotion—indeed, what else would we be driven by? People who lose the capacity to feel emotion don't become paragons of rationality ala Spock or Lt. Com. Data; they become inert, crippled by flat affector even catatonia. Emotions drive almost all our behavior, rational and otherwise; and it is ultimately the emotional experiences of joy and suffering that are the foundation of rationality itself. Emotions can be rationally warranted or unwarranted in much the same way as beliefs: If a brown recluse spider is attacking you, fear is rational. If a common house spider is crawling along the wall, fear is irrational—we call that "arachnophobia". If your grandmother just died, sadness is rational. If your life is going fine but you can barely get out of bed, your sadness is irrational—we call that "depression". Even happiness can be irrational: You'd have to be manic to laugh with glee while under aerial bombardment. In fact most people's emotions are rational most of the time.
This is reason for optimism; while the project of human rationality may seem hopeless at times, we have made substantial progress even in the last few generations. Perhaps one day the entire world—or entire colonized Orion Arm—will be an idiot-free zone.
[The image is a public domain brain scan image from the National Institute of Mental Health, highlighting one of the amygdalas, one of the central features of our limbic system, which is, broadly speaking, the source of our emotions. The amygdalas are involved in memory, decision-making, motivation, and emotion—making them a particularly good place to start when asking how rational
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