^A The use of “exploit” here has unfortunate overtones in terms of “exploiting others.” What is meant here by “exploit” is simply using the knowledge one has learned from exploring to make the best choices.

^B Machine learning is a branch of computer science in which algorithms are developed to learn from the world.³ Although machine learning often lives in the artificial intelligence divisions of computer science departments, machine learning is actually distinct from artificial intelligence. “Artificial intelligence” is about trying to match (either mechanistically or computationally) human skills. “Machine learning” is about trying to build the best algorithm that will be able to solve the problem. Scientists working on machine learning believe that a machine that can learn from the world can be more efficient and perform better than a preprogrammed machine. (For example, imagine if your thermostat could learn when you typically came home or when you typically woke up in the morning. It could learn to set itself to warm the house before you arrived or just before you woke up. Of course, it could be programmed to do that, but then it would have to be programmed separately for each person. A single learning algorithm could be programmed once to learn the right timing for each person.⁴)

^C This can be most easily implemented by selecting a random number from 1 to 100 each try. If the random number is 100, then you take a random action. If it’s anything else, you pick the best choice you can. One could also simply pick the random action every 100th try, but the danger is that if the winning probabilities have some oscillation to it, then your every 100th try might match the oscillation and you wouldn’t know. Randomness is better. Of course, humans are terrible at being random.⁵

^D Yes, I know slot machines always have a less than 100% payout because the goal of casinos is to make a profit. If you like, you can think of these games as putting money into savings accounts. A savings account in a bank may be FDIC insured and thus very safe (because the only way to lose money is for the United States itself to go under), but you’d make only 1% interest each year. On the other hand, a mutual fund account might not be FDIC insured (and thus you can lose money on it), but you might make an average of 5% interest each year. Buying a stock might be very variable, making 10% one year and losing 10% the next. This is why good financial planning requires a diverse portfolio to balance out risk.⁹ $1 if you pick a blue marble. Imagine that you see the first jar being filled, so that you know that half of the marbles are red and half are blue. (You will still have to pick with your eyes closed and the jar above your head so which marble you pick will be random, but you know the distribution of marbles in the first jar.) Imagine, however, that the second jar was filled while you were not there and all you know is that there is a mix of red and blue marbles. Which jar will you pick from? In the first one, you know that you have a 50:50 chance of getting red or blue. In the second one, you might have a 90:10 chance or a 10:90 chance. Adding up all the possible chances, it turns out that you also have a 50:50 chance of getting red or blue. (The likelihood of seeing a 90:10 mix of red and blue marbles is the same likelihood of seeing a 10:90 mix. Since 90:10 is the opposite of 10:90, they average out to being equivalent to a 50:50 mix in both the first-order average [expected value] and the second-order variability [risk].) However, people reliably prefer the first jar, even when the fact that the second jar adds up to the same chance is pointed out to them. The first jar contains risk (expected uncertainty; you could get red or blue). The second jar, however, also contains ambiguity (What’s the mix?) as well as risk (What’s the variability?). This is known as ambiguity aversion and is technically an example of the Ellsberg paradox.^E

^E The paradox was introduced by Daniel Ellsberg (of the famous Pentagon Papers¹⁹) in his 1962 Ph.D. dissertation in economics.²⁰ It is called a paradox because the simple equations of economists are unable to explain why humans are ambiguity averse.

^F To my knowledge, although the paradox is robustly shown by humans, the paradox has not been tested on nonlinguistic animals, probably because it depends on the experimenter telling the subject the two probabilities.

^G These rules were put in place due to egregious experiments such as the Tuskegee syphilis experiment, where subjects were lied to about the goals and consequences of experiments.²² These rules are now followed very strictly, and it is exceptionally difficult to get approval to lie to an experimental subject.

^H There is some evidence that part of the problem with psychopaths may be due to dysfunction in this mirror system and its ability to recognize the emotions of others,³⁷ but others have argued that this dysfunction is due primarily to an inability to correctly represent socially derived internal emotions.³⁸

^I One probably should not make a distinction between “classic” and “popular.” Most literature that we call “classic” now was immensely popular in its time. Shakespeare, for example, was by far the most popular playwright of his day, and his plays are full of rough jokes for the popular crowds. (See, for example, Mercutio’s death scene in Romeo and Juliet, most of A Midsummer Night’s Dream, and the porter in Macbeth, to name but three.) I’ve often thought Shakespeare at his time was probably closest to Steven Spielberg in our day, with both blockbuster adventures like Indiana Jones and critically acclaimed movies like Schindler’s List. Similarly, the entire city of Athens turned out for the annual shows by Aeschylus, Sophocles, and Euripides, each of whom regularly won the best-play awards. Aristophanes’ comedies contain what we now refer to as “frat-boy” humor, with lots of sex (Lysistrata), over-the-top characters (The Clouds), and fart jokes (The Frogs).

^J An interesting question arises when the characters are explicitly nonhuman, whether they be aliens, magical creatures, or robots. In these stories, the nonhuman creatures tend either to be based on specific human cultures or to have exaggerated but still remarkably human, traits.⁴¹ Writing science fiction about aliens can be said to be about finding the balance between making the aliens too human and making them too alien.

^K As I’ve said elsewhere in this book (see Chapter 24 for a detailed discussion), the recognition that there are physical and evolutionary causes for increased risk-taking in adolescents does not excuse the adolescent from the responsibility for his or her actions. It is important to recognize that sociobiological trends are not destiny and do not relieve one of responsibility. Although most drug users start using drugs in their adolescent years and many drug users age out of drug use and settle down to normal (non–drug-based) lives, the vast majority of adolescents do not succumb to peer pressure and drug use.⁴⁶ One hopes that before being sent off to college or out into the world for their exploration, adolescents have been taught what their limits are and have an accurate sense of the risks and dangers.