Algorithms to Live By: The Computer Science of Human Decisions

by Brian Christian

Optimal stopping tells us when to look and when to leap. The explore/exploit tradeoff tells us how to find the balance between trying new things and enjoying our favorites. Sorting theory tells us how (and whether) to arrange our offices. Caching theory tells us how to fill our closets. Scheduling theory tells us how to fill our time.

As computers become better tuned to real-world problems, they provide not only algorithms that people can borrow for their own lives, but a better standard against which to compare human cognition itself. Over

Unlike previous researchers, Gittins approached the multi-armed bandit problem in those terms. He conceived the goal as maximizing payoffs not for a fixed interval of time, but for a future that is endless yet discounted.

Exploration in itself has value, since trying new things increases our chances of finding the best. So taking the future into account, rather than focusing just on the present, drives us toward novelty.

In 2010 and 2015, the FDA released a pair of draft “guidance” documents on “Adaptive Design” clinical trials for drugs and medical devices, which suggests—despite a long history of sticking to an option they trust—that they might at last be willing to explore alternatives.

but as Andy Warhol put it, “A Coke is a Coke.” Having instincts tuned by evolution for a world in constant flux isn’t necessarily helpful in an era of industrial standardization.

We refer to things like Google and Bing as “search engines,” but that is something of a misnomer: they’re really sort engines. What makes Google so dominant as a means of

The truncated top of an immense, sorted list is in many ways the universal user interface. Computer science gives us a way to understand

A team of researchers at the University of Rochester recently explored how prior experiences might affect behavior in the marshmallow test. Before marshmallows were even mentioned, the kids in the experiment embarked on an art project. The experimenter gave them some mediocre supplies, and promised to be back with better options soon. But, unbeknownst to them, the children were divided into two groups. In one group, the experimenter was reliable, and came back with the better art supplies as promised. In the other, she was unreliable, coming back with nothing but apologies. The art project completed, the children went on to the standard marshmallow test. And here, the children who had learned that the experimenter was unreliable were more likely to eat the marshmallow before she came back, losing the opportunity to earn a second treat. Failing the marshmallow test—and being less successful in later life—may not be about lacking willpower. It could be a result of believing that adults are not dependable: that they can’t be trusted to keep their word, that they disappear for intervals of arbitrary length. Learning self-control is important, but it’s equally important to grow up in an environment where adults are consistently present and trustworthy.

Just amazing!

And the challenge has only increased with the development of the printing press, the nightly news, and social media—innovations that allow our species to spread language mechanically.

Communication is one of those delightful things that work only in practice; in theory it’s impossible.

It offers a way to have finite patience and infinite mercy. Maybe we don’t have to choose.

Shortly after being sworn in to Hawaii’s First Circuit Court, Judge Steven Alm noticed a remarkable pattern. Probationers would repeatedly violate their probation terms, and circuit judges would routinely use their discretion to let them off with a warning. But at some point, perhaps after a dozen or more violations, the judge would decide to be strict, and assign the violator a prison sentence measured in years. Says Alm, “I thought, what a crazy way to try to change anybody’s behavior.” So Alm proposed almost exactly the opposite. In place of violation hearings scheduled a long time into the future, requiring uncertain judgment calls, and occasionally producing huge penalties, HOPE is based on immediate, predefined punishments that begin with just one day in jail and increase after each incident. A five-year study by the Department of Justice reported that HOPE probationers were half as likely as regular probationers to be arrested for a new crime or have their probation revoked. And they were 72% less likely to use drugs. Seventeen states have followed Hawaii’s lead and launched their own versions of HOPE.

As Laurence J. Peter saw it, the insidious Peter Principle arises in corporations because of “the first commandment of hierarchical life: the hierarchy must be preserved.” TCP, in contrast, teaches the virtues of flexibility. Companies speak of “flat” hierarchies and “tall” hierarchies, but they might consider speaking of dynamic ones. Under an AIMD system, no one is long anxious about being overtaxed, nor long resentful about a missed promotion; both are temporary and frequent correctives, and the system hovers near its equilibrium despite everything changing all the time. Perhaps one day we’ll speak not of the arc of one’s career, but rather of its sawtooth.

Understanding the exact function and meaning of human backchannels continues to be an active area of research. In 2014, for instance, UC Santa Cruz’s Jackson Tolins and Jean Fox Tree demonstrated that those inconspicuous “uh-huhs” and “yeahs” and “hmms” and “ohs” that pepper our speech perform distinct, precise roles in regulating the flow of information from speaker to listener—both its rate and level of detail. Indeed, they are every bit as critical as ACKs are in TCP. Says Tolins, “Really, while some people may be worse than others, ‘bad storytellers’ can at least partly blame their audience.” This realization has had the unexpected side effect of taking off some of the pressure when he gives lectures—including, of course, lectures about that very result. “Whenever I give these backchannel talks, I always tell the audience that the way they are backchanneling to my talk right now is changing what I say,” he jokes, “so they’re responsible for how well I do.”

The most prevalent critique of modern communications is that we are “always connected.” But the problem isn’t that we’re always connected; we’re not. The problem is that we’re always buffered. The difference is enormous.

I’m an optimist in the sense that I believe humans are noble and honorable, and some of them are really smart.… I have a somewhat more pessimistic view of people in groups. —STEVE JOBS

(Luring an opponent into fruitless recursion can be an effective strategy in other games, too. One of the most colorful, bizarre, and fascinating episodes in the history of man-vs.-machine chess came in a 2008 blitz showdown between American grandmaster Hikaru Nakamura and leading computer chess program Rybka. In a game where each side got just three minutes on the clock to play all of their moves or automatically lose, the advantage surely seemed to be on the side of the computer—capable of evaluating millions of positions every second, and of making its move without twitching a muscle. But Nakamura immediately gridlocked the board, and proceeded to make repetitive, meaningless moves as fast as he could click. Meanwhile, the computer wasted precious moments fruitlessly searching for winning variations that didn’t exist and doggedly trying to anticipate all the possible future moves by Nakamura, who himself was simply doing the chess equivalent of twiddling his thumbs. When the computer had nearly exhausted its time and began flailing so as not to lose by the clock, Nakamura finally opened the position and crashed through.)

When it comes to traffic of the human kind, the low price of anarchy cuts both ways. The good news is that the lack of centralized coordination is making your commute at most only 33% worse. On the other hand, if you’re hoping that networked, self-driving autonomous cars will bring us a future of traffic utopia, it may be disheartening to learn that today’s selfish, uncoordinated drivers are already pretty close to optimal. It’s true that self-driving cars should reduce the number of road accidents and may be able to drive more closely together, both of which would speed up traffic. But from a congestion standpoint, the fact that anarchy is only 4/3 as congested as perfect coordination means that perfectly coordinated commutes will only be 3/4 as congested as they are now. It’s a bit like the famous line by James Branch Cabell: “The optimist proclaims that we live in the best of all possible worlds; and the pessimist fears this is true.” Congestion will always be a problem solvable more by planners and by overall demand than by the decisions of individual drivers, human or computer, selfish or cooperative.

Nature is full of examples of individuals being essentially hijacked to serve the goals of another species. The lancet liver fluke (Dicrocoelium dendriticum), for instance, is a parasite that makes ants deliberately climb to the tops of grass blades so that they’ll be eaten by sheep—the lancet fluke’s preferred host. Likewise, the parasite Toxoplasma gondii makes mice permanently lose their fear of cats, with similar results.

Yes, people search for objective characteristics they care about. Everybody wants somebody who’s kind and intelligent and interesting and healthy and maybe physically attractive, good earning power, the whole laundry list of features, but that’s the first pass.… After you’ve spent enough time together, it’s not those things that make you want

Whenever you find yourself on the side of the majority, it is time to pause and reflect. —MARK TWAIN

I firmly believe that the important things about humans are social in character and that relief by machines from many of our present demanding intellectual functions will finally give the human race time and incentive to learn how to live well together. —MERRILL FLOOD Any dynamic system subject to the constraints of space and time

But we don’t only pick the problems that we pose to ourselves. We also pick the problems we pose each other, whether it’s the way we design a city or the way we ask a question. This creates a surprising bridge from computer science to ethics—in the form of a principle that we call computational kindness.