[PROLOGUE – EVERYBODY WANTS A ROCK]
[PART I – THERMOSTAT]
[PART II – MOTIVATION]
[PART III – PERSONALITY AND INDIVIDUAL DIFFERENCES]
[PART IV – LEARNING]
[PART V – DEPRESSION AND OTHER DIAGNOSES]
[PART VI – CONFLICT AND OSCILLATION]
[PART VII – NO REALLY, SERIOUSLY, WHAT IS GOING ON?]
[INTERLUDE – I LOVE YOU FOR PSYCHOLOGICAL REASONS]
[PART VIII – ARTIFICIAL INTELLIGENCE]
[PART IX – ANIMAL WELFARE]

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Since behavioral feedback of any significance is always negative, it follows that there will always be a tendency to move toward a zero-error condition calling for no effort, and (if clever enough) one will always be able to discover the reference condition. By the same token, one will always be able to discover what the subject is controlling, for if disturbances are applied that do not in fact disturb the controlled aspect of the environment, the subject’s behavior will not oppose the disturbance. Only when one has found the correct definition will the proposed controlled quantity be protected against disturbance by the subject’s actions.

— William Powers, Behavior: The Control of Perception

What we wrote in the previous parts is only a start. Here are the things we need to figure out next.

First, we should try to discover all the basic drives of human psychology. We should learn about their error signals, which we identify as emotions. 

When possible, we should also figure out what signal each governor is actually controlling, and the target it is controlling that signal towards. It’s a good start to know that there is a drive with an error we know as thirst, but it would be better to confirm that thirst is the error of a governor controlling blood osmolality. And it would be even better to then confirm that this governor controls blood osmolality towards a target of 280-295 mOsm/kg (or perhaps some biological proxy of that target). 

For example, we may find that there is a hunger governor controlling the hormone leptin, a tiredness governor controlling the hormone melatonin, and so on. The answers we find probably won’t be quite that simple, but we’re looking for something along these lines. 

We should also try to characterize signals like happiness and curiosity, which don’t seem to be errors from a control system (if nothing else, they aren’t actively driven towards zero!), but do seem to be important signals that interact with the other drives and with motivation in other ways.

Second, we should try to discover the parameters that tune the governors. It’s clear that some governors can be “stronger” than others, and that these patterns of strength and weakness differ between different people. People are more or less brave, more or less neat and clean, etc. We’d like to find out what it means, in a precise sense, for one governor to be stronger than another. 

We’d like to know whether parameters are individual to each governor, or global to all of them, or if there are some of both. For example, we’d like to know if each governor has an individual parameter that adjusts how it balances exploration vs. exploitation, or if there is an explore/exploit parameter that influences all the governors globally. 

One of our long-term goals is to find ways of measuring these parameters for each person. For example, we might want to ask if someone’s fear governor is stronger than their thirst governor, perhaps even how much stronger. This will give us the start of a true measure of personality. 

Third, we will want to discover the laws of what’s known as selection, the detailed parliamentary procedure and rules that control how the governors vote on actions. 

As before, there will be parameters that adjust these laws, and make people different from one another. Learning how to measure these parameters will give us an even stronger theory of personality.

Fourth, as we develop a better understanding of the drives, the governors, and the laws that dictate their behavior, we can start working to characterize well-known behaviors in terms of these governors and their parameters. 

Here are some things we might be able to understand in terms of this new paradigm: personality, anxiety, depression, personality disorders, possibly other psychiatric disorders, self-harm, high-risk behavior, drugs, and addiction. 

If cybernetic principles lead to models that have natural outcomes that look just like anxiety, depression, addiction, etc., that will establish the promise of this approach. Then we can look at the points where the models fail, consider alternative models, refine the approach, and make the models even better. 

But this last project is kind of “for the rest of time”. If building the paradigm is successful, people can spend the next few hundred years applying it. But first we have to build it.

1. Considerations

First, a few considerations, issues that might come up when trying to discover the drives.

1.1 Are Emotions Constructed?

One of the questions academics keep asking about emotions is whether or not they are “culturally constructed”. 

This may seem like a weird question, but to people on the inside of academic psychology, it’s a major topic.

But we’re not here to revisit those debates, we’re here to put them to rest. The cybernetic perspective gives a very clear answer to the question of whether or not emotions are constructed: yes, and no.

All emotions are biologically hard-wired, because they are the error signals from our most fundamental drives, all of which are necessary for survival. These are not at all constructed. While we don’t yet know the details, we understand that at some level they are physically distinct from each other, controlling different biological signals towards different set points. 

But emotion categories are culturally constructed. There are a huge number — dozens, maybe hundreds, maybe even thousands — of individual emotions, but we don’t have a word for each of them. Instead we group them together in ways that make practical sense for the needs of our culture. 

As usual, hunger is a good example. We treat hunger as if it is just one signal, when in fact hunger is easily a dozen different emotions, maybe more. But because these emotions are all addressed by similar actions (stuffing something in your maw) most languages treat them as one thing.

We can unpack our emotion words when we need to — we can talk about craving salt, or talk about specific cravings that come from this drive, like craving pickles. We can say things like, “I’m stuffed but I’m still hungry!” and so on. But the hunger drives are closely intertwined most of the time, so most languages don’t make any serious distinction between them.

Desert mice almost never drink water; they get almost all their water from their food, from eating seeds. So if desert mice developed a language, they would probably come up with a single word that meant both hungry and thirsty. In their experience, hunger and thirst are addressed by one action, eating seeds, and it’s more useful to combine these ideas than to keep them separate. 

No group of humans is as extreme as the desert mouse — but still, we do wonder if there are cultures where people get most of their water from their food, and if those cultures would bother to distinguish between hunger and thirst, or if they would have one word covering both. 

1.2 Redundancy

Basic needs, especially needs that are critical to our survival, are probably supported by more than just one drive. 

Elevators are designed not only to support the weight they were designed to carry, but to support many times that weight, and they have multiple brakes and other failsafes in case of crisis. If one brake or failsafe malfunctions, the others kick in to prevent disaster. 

For the same reason, we should expect drives to be redundant, sometimes massively redundant. Humans tend to create systems that are highly efficient but fragile. But nature tends to create systems that are inefficient but resilient. If an animal has only one drive that tells it to eat, then if anything goes wrong with that drive, it will die. Better to have multiple drives, so that the animal is able to survive even if it is born with a surprise mutation or gets an unexpected brain injury. 

The more important a need is to survival, the more likely it is that there will be built-in redundancy. A need that is critically important may be supported by not one governor but by many separate governors that all control different measures of the same need. 

2. Observational Methods

One of the most foundational projects is to discover the list of drives and emotions. Above anything else, we should figure out how many different drives there are, and do our best to identify each of them. 

We can do this in two ways. We can use methods that are observational (looking at historical data, case studies, etc.) and methods that are empirical (let’s collect some data). Let’s look at these methods one at a time, starting with observational methods. 

2.1 Pure Observation

We can draw a lot of reasonable conclusions about the list of drives based on our everyday experiences of what it’s like to be human, and what we know about what it takes to survive. 

For example, we know that people have drives that lead to hunger and pain because we all experience those emotions, and it’s clear that they motivate our behavior. Most behaviors you encounter can be explained in terms of a basic drive.

Drives aren’t linked directly to each specific behavior, of course. There isn’t a drive to watch operas, or to play shuffleboard. For one thing, those options didn’t exist for our ancestors. People are probably driven to do these things because of some kind of general social emotions. But any behavior that can’t be explained in terms of a known basic drive may point to a basic drive of its own.

For example, it seems possible that humans have a basic drive to look at animals. As strange as this might sound, we go to great lengths to look at animals, even in private when no one else is around, even when no one is watching, and it seems like we are driven to this for no other reason than to look at them. It’s hard to explain these behaviors in terms of another drive, so the drive to look at animals may itself be basic. 

Think about all the time, space, and money we spend on zoos. Think of how we plaster the walls of our kindergartens with pictures of lions. Think of how many hours you personally have spent watching nature documentaries, or animal videos on YouTube. 

Before dog people got online, everyone knew that cat pictures ruled the internet. Animal pictures still rule the internet. As of this writing, the subreddit r/aww (mostly pictures of animals) is the 6th largest subreddit, with 37 million members. This may also be why people get pets in the first place, so they have animals to look at whenever they want.

If the desire to look at animals is a drive, then it should be homeostatic and conserved; you should want to go to the zoo for a while, then you should be ready to go home. If we keep you from going to the zoo, you will look at geese in the park instead. And if we keep you from looking at any animals at all, you may eventually become nearly frantic with your desire to do so, especially if this drive is unusually strong in you.  

Games like 2048 and Candy Crush suggest that there might be some kind of drive that causes sorting behavior, though maybe this is just an unusual manifestation of a drive for decorating or cleaning your environment. 

Like, let’s draw out how weird it is that people play these games. What the fuck is going on? Why is it so engrossing to watch two little blocks labeled “2” combine to form a block labeled “4”? People will do this for hours. It sounds so dumb, and yet when you’re on a plane sitting behind someone playing this on their seatback screen, you can’t look away.

When we find something extremely engrossing, it might be because it has concentrated the exact thing our drive is trying to control. If the drive here is something like “sorting”, there aren’t many naturally-occurring situations where you’re only sorting. But a game can provide you with pure, unadulterated sorting. (Compare: superstimuli.)

Another unlikely drive is some kind of drive to dig holes. The strongest evidence for this is in hobby tunneling, where people wake up one day and start digging vast networks of tunnels, usually for no apparent reason. They often do their digging in secret, and they’ll keep doing it even if there is a social or material cost, even when it’s forbidden. This suggests that it’s not done for social reasons, but in fact is done in spite of them.

What else could explain the incredible popularity of Minecraft? Why would children flock to a game about digging, instead of a game about anything else? As they say, the children yearn for the mines. 

When it is hard for us to do an activity itself, watching the activity can sometimes serve as an acceptable substitute. In this way, a drive for excavation might explain what the Italians call umarell. You’ve probably seen them — old men who spend their days watching construction sites, especially dig sites, standing there entranced with their hands clasped behind their back. This is enough of a universal across time and space that Jerry Seinfeld even has a bit about it.

Of course, these Italian men are so old-fashioned. Today the boys get all their construction watching on TikTok: 

There may even be a drive to seek out weapons, expressed especially strongly in boys. If you have ever been a boy, or spent any time around boys, this will probably sound familiar. Check out this passage from the Cyropaedia, a 370 BC biography of Cyrus the Great: 

And to-day a battle is before us where no man need teach us how to fight: we have the trick of it by nature, as a bull knows how to use his horns, or a horse his hoofs, or a dog his teeth, or a wild boar his tusks. The animals know well enough,” he added, “when and where to guard themselves: they need no master to tell them that. I myself, when I was a little lad, I knew by instinct how to shield myself from the blow I saw descending: if I had nothing else, I had my two fists, and used them with all my force against my foe: no one taught me how to do it, on the contrary they beat me if they saw me clench my fists. And a knife, I remember, I never could resist: I clutched the thing whenever I caught sight of it: not a soul showed me how to hold it, only nature herself, I do aver. I did it, not because I was taught to do it, but in spite of being forbidden, like many another thing to which nature drove me, in spite of my father and mother both. Yes, and I was never tired of hacking and hewing with my knife whenever I got the chance: it did not seem merely natural, like walking or running, it was positive joy.

Consider this collection, and what could possibly have driven someone to put it together with such care: 

People seem stuck on the idea that complex behaviors like digging or pretending a cool stick is a weapon couldn’t possibly be innate. But obviously they can be. Breeds of dogs whose ancestors were bred to herd animals, will herd animals without having to be taught. Spiders spin webs. People usually become attracted to adult members of the same species, rather than becoming attracted to furniture or the moon. If evolution has enough discretion to latch our sexual drives onto reasonable targets most of the time, then surely it can latch other drives onto other complex targets, like a stick that reminds you of an AK-47.

While we can see evidence of these drives as they express themselves in specific kinds of behavior, we don’t immediately know what is actually being controlled. A drive to dig might be implemented as something like a drive to smell freshly-turned earth, because in general that target would lead to digging behavior. You could imagine how tangential behaviors, like gardening, might be other, confused results of this drive. 

2.2 Ecological 

We can also draw some reasonable conclusions from our understanding of biology. 

All of our psychological drives were put into us by evolution to help keep us alive. So generally speaking, we should find in ourselves at least one drive (and matching emotion) for each thing that we need to stay alive, and at least one drive for all the things that have been necessary to be evolutionarily successful. 

You need to eat to stay alive, which is another reason to expect at least one drive for hunger. You don’t need sex to stay alive, but the species does need a sex drive to go on being a species at all, which is why evolution made us horny. Things that are necessary for survival (like breathing and sleeping) must be backed up by drives.

However, there are a few drives that are conspicuously missing — we don’t have quite every drive we need. See the example of scurvy, the horrible disease caused by a deficiency of vitamin C. You might think that people suffering from scurvy would seek out foods that contain the thing they lack, but as far as we know they don’t crave lemons or cabbage, which is why the cure took so long to discover. Vitamin C is necessary for survival, but people don’t appear to have a drive to seek it out.

There seem to be two main reasons we lack this drive.

First, most foods contain at least a little vitamin C, so most of our ancestors would have survived just fine without a drive telling them to seek it out. If you eat any kind of normal diet, you’ll end up with plenty of vitamin C by default. Only in very weird situations where you get no fresh food at all, like being a 15th century mariner or an arctic explorer, does this become a problem.

Second, this is a specific case where humans happen to be very unusual. We are one of the very small number of animals that can’t synthesize our own vitamin C, which is why we need to find it in our food. Most animals don’t need to consume any vitamin C, they make their own, so most animals would have no need for vitamin C drive at all. 

We probably inherit most of our drives from designs that are common to all mammals, and since the default mammal package doesn’t include a drive for vitamin C (because most mammals make their own), humans would have had to evolve such a drive from scratch. But given that vitamin C is so abundant in everything we normally eat, it’s easy to imagine why we didn’t bother.  

We have a vegetarian friend who used to struggle with random fatigue and low energy. Then he tried taking vitamin B12, and immediately felt a huge difference. But he didn’t seem to crave foods high in B12 before, suggesting that vitamin B12 also lacks a governor, despite being an essential nutrient.

This may be a common feature of many vitamins — in fact, it may be part of what it means for us to call something “a vitamin”. Most vitamins were discovered by people trying to cure diseases of deficiency, where people weren’t getting enough of the vitamin. It’s hard to develop a deficiency of something you have a drive for — the deficiency and the cure will be really obvious, since you’ll develop cravings. If you have a drive for some substance, it will be hard to develop a deficiency, so it may not be classified as a vitamin.

Some essential minerals probably have governors, but others may not, and it’s not entirely clear which is which.

But there will be signs. If you have a drive for a mineral, it should be pretty hard to develop a deficiency in that mineral, since you will normally be driven to consume it. But if you don’t have a drive for a mineral, then just like with vitamins, you’re at risk of developing deficiencies in that mineral, since you don’t have any natural motivation to seek it out. If there’s a mineral that people are always getting deficient in, that’s probably a sign that it doesn’t have a drive.

Iodine is a necessary mineral — if you don’t get enough, you develop terrible diseases of deficiency, especially goiter. This happens pretty frequently, or at least it did until people discovered the connection and started supplementing salt with iodine. Again this seems like possible evidence that there’s no iodine drive and no iodine governor. If there were, then all these Swiss people suffering from goiter would have been sitting around in their mountain cabins going “damn I would kill for some seafood right now” (seafood is high in iodine). On the other hand, maybe they were saying that, and history simply didn’t record it.

This seems like the kind of thing we should already have a clear answer for, but the literature on iodine is pretty unclear — there are a few studies, like this one that says that children aged 8-10 can’t tell the difference between traditionally prepared pickles made with iodized salt and traditionally prepared pickles made with non-iodized salt. Most of the existing research agrees, though there isn’t much of it. 

But we’ve collected a bit of data on this already, and found that while most people indeed seem unable to distinguish between iodized and non-iodized salt, a few people can pick them out of a lineup at rates somewhat better than chance. It’s also possible that most people can’t distinguish between iodized and non-iodized salt because most people aren’t iodine deficient, so that drive is inactive. 

Another slightly odd possibility is that maybe some people have iodine governors and other people don’t. Maybe this depends on where your ancestors lived, and whether they naturally got iodine in their diet (like if they were fisherpeople) or whether they had to actively seek it out to get enough (#hillpeople).

We are probably “missing” some other governors, especially governors for things that are not necessary to stay alive per se, but things that would be nice to have. 

For example, there appears to be no emotion that drives us to go and get more sunshine. Lack of sunshine is pretty bad for you, but there’s just no system making sure you go out and get it. Just like vitamin C, our ancestors were exposed to so much sunlight that evolution never bothered to give us a sunlight drive. 

This is why you have to use your human intellect, or a phone reminder or something, to remember to get your daily sunlight. You have a hard time building an association between sunlight and health because you don’t have a dedicated system keeping tabs on it.

2.3 Resistance

Another way to identify the drives is to ask ourselves what kinds of things make people angry when you try to stop them from doing those things. 

This provides some justification for drives like privacy and territoriality. Most people will go nuts if they’re not allowed some amount of personal territory; think of the teenager with the STAY OUT sign on their door.

This is also the reason to believe in various social emotions, like an emotion that arises when we feel we are being taken advantage of. This governor has a target that’s something like “I am doing 1/x of the work in this group, where x is the number of people in this group”. If you are doing more than your fair share of the work, very far from this target, then you get an error signal that feels something like being exploited, or being played.

This is why roommate situations are so stressful. People have different setpoints for cleanliness, and you might expect that each person would just clean the apartment up to their preferred level. An animal that had no social emotions would probably do exactly that. But people are social animals, and for people living in groups, the desire for cleanliness is in conflict with the desire not to get taken advantage of. 

We can also take the argument from depression in reverse. When someone is in the depths of a serious depression, we think that’s a result of all of their drives being turned way down. What do people conspicuously stop doing when they are depressed? The answer is hygiene. They let both their body and their living space become unkempt, even filthy. 

If you try to stop someone from getting/doing something, and they resist, that’s a drive. This is useful when, like privacy, it may not appear that they’re actively doing anything. But a drive for privacy becomes apparent when you don’t let people have it, because then they will fight for it. 

2.4 Knockout

Sometimes a drive is conspicuously absent in a few individuals, throwing into stark relief the fact that it’s present in everyone else. This can give us a surprisingly clear picture of the missing drive — the shape of something can be more obvious from its absence than its presence (or at least you can learn different things about its shape from the absence).

Cases of total or near-total knockout, where a person or animal is entirely missing a drive or an emotion, provide pretty strong evidence that the drive is present in everyone else. Consider the patient known as SM-046, a woman with severe amygdala damage, who experiences almost no fear:  

While the researchers behind this study don’t seem to understand its significance, we see this as strong evidence that fear and suffocation are separate emotions arising from separate drives.

SM has a complete fear knockout, and never experiences fear, no matter how dangerous the situation. She just doesn’t have that governor, or her copy of the governor is totally turned off. But she will still feel “air hunger” when she is suffocating, because breathing is handled by a different governor. It produces an entirely different error signal, one that’s easy to mistake for fear if you’re not looking carefully. 

Fear is pretty important to survival, so it seems like one of those cases where you might expect evolution to have added some redundancy. It seems reasonable to have different fear governors for different things, so if you knock your head wrong once and are no longer afraid of snakes, at least you’re still afraid of tigers. But SM doesn’t seem to have any backup fears that are still online. 

This suggests two possibilities. 1) Maybe there is really only one governor that accounts for every kind of fear. SM isn’t just missing some kinds of fear, she’s missing every kind, because there’s a single point of failure. 2) There are multiple fear governors, but they are organized in a way where it’s possible to knock all of them out at once. For example, maybe there are multiple governors but her ability to generate the perception of danger is knocked out, so all the governors are totally inactive. 

There are also some very rare genetic conditions that leave people with no experience of physical pain. These conditions are very rare because pain is very important. Without pain, you usually die, because you have no motivation not to put your arm in a wood chipper. One patient said, “at a young age, I would like to bang my head against the wall because I liked the feeling of vibration”.

This suggests that like fear, pain might be a single emotion, because it can be so cleanly toggled on or off. As far as we know, there aren’t genetic conditions where you can feel burning but you can’t feel cutting, or vice versa. People seem to either have pain basically working or have it basically gone, across the board.

That said, there do appear to be shades of pain insensitivity. For example, Jo Cameron has a version of pain insensitivity where she still experiences pain in the sense that she can avoid harming herself, but her subjective experience of pain isn’t at all unpleasant. She can tell that she’s been burned or cut, but she doesn’t mind. She described childbirth as “a tickle”, and said, “I could feel that my body was changing, but it didn’t hurt me.”

While Jo’s case is extreme, this kind of variation seems common. Some people experience pain but don’t mind, and other people don’t notice at all, and also there are shades between. So maybe there are tightly-linked drives or subcomponents that can eventually be distinguished with enough examination.

Extreme personality disorders may also be a kind of knockout. The average psychopath behaves a lot like a person with weights near zero on certain social governors, the governors that normally make people feel emotions like empathy and shame. 

Compare the stories of patient SM and Jo Cameron to this podcast interview with the sociopath M.E. Thomas / “Jamie”. There’s a lot of interesting stuff in here, but we want to highlight this one section where Spencer, the interviewer, asks her about fear:

SPENCER: I know a handful of sociopaths, and one thing I’ve asked them about is fear. Some of them say that they don’t think they have fear, or at least not in the normal way that other people do. What’s your relationship with fear?

JAMIE: Yeah, I totally agree with that. … Sometimes that’s gotten me in trouble because I will not take adequate precautions. Sometimes I do things that can maybe seem like I’m a little accident-prone. For instance, when I go mountain biking, I probably crash like 20% of the time, which I’ve heard is high.

SPENCER: Yeah, you mention in your book how you cut yourself in the kitchen a lot with knives by accident. Can you talk about that?

JAMIE: Yes, I still have a plastic safety knife. It’s kind of like the type that you carve pumpkins with, or little children can carve pumpkins with. I almost always use that knife. Here and there, I think it actually is safer for me to just use a bigger metal knife, but then I have to be very, very conscientious. I’m the same way too with train tracks. There are some train tracks close to where I live, and I cross them basically every day, but I know that I’m bad at paying attention and being careful for my own self. So I really talk to myself when I’m doing it, I’m like, “Here we come, 15 feet from the train tracks, 10 feet from the train tracks. Look right, left, right, left, right.” It’s this very belt and suspenders approach to kind of rein in my brain, which naturally doesn’t care, doesn’t even pay attention to things like that.

Sometimes psychopaths like to say that they are more rational than other people, like in this excerpt: 

JAMIE: I think you can always cooperate with psychopaths when your incentives align, and when you’re able to convince a psychopath that the incentives do align, then the psychopath is a very good team member.

SPENCER: And why are they a good team member?

JAMIE: Because once their incentives are aligned that way, they’re almost like a robot. They will always behave in a way that is in alignment with their incentives. Essentially, you can trust — in economics, they talk about the rational actor, who always behaves rationally — in a lot of ways, the psychopath, as long as they’re not experiencing gray rage or maybe some weird hormones or a situation like that, they basically are the economic rational actor.

But assuming self-preservation is one of your values, what is so rational about crashing 20% of the time you go mountain biking? 

A different interpretation is that psychopaths aren’t more rational, but they are less conflicted. What they describe as a lack of ego is perhaps a lack of the self-suppressing social emotions that include certain types of fear of social consequences (for example, shame). 

In a normal person, these prosocial emotions are in conflict with selfish desires that might lead someone to cheat, lie, steal, and so on. But psychopaths mostly lack these emotions, they are entirely un-self-conscious. This means that they feel little hesitation to bend the rules. But it also has the relaxing side effect of leading to less inner conflict, which might make one feel very rational. After all, the experience is of having clear desires and working towards them without any second thoughts.

This might also be why psychopaths are often so charming and charismatic — we find a lack of inner conflict very attractive, the lack of tension even showing in your face.

3. Empirical Methods

So far we’ve looked at observational techniques only. Now we’re gonna get off our asses and (describe how to) collect some data. Here’s how we might do it.

3.1 Artificial Knockout

Natural knockouts are the clearest-cut examples, and teach us the strongest lessons. But we can learn similar lessons by knocking out emotions artificially, like with drugs.

Drugs don’t usually seem to reduce the weight on a governor to zero. But they do often seem to turn the weight (or error) on a drive down, and sometimes they seem to turn it up. For example, alcohol seems like it temporarily reduces the weights on the fear and the shame governors, making people less driven by fear and shame. In contrast, it doesn’t seem to have much impact on the hunger governor. Drunk people seem just as hungry as normal. Or maybe alcohol turns hunger up; it seems like everyone wants fried food after a couple of pints, but maybe this is driven more by the sudden lack of shame.

Sometimes the changes caused by drugs are what we would normally think of as “side effects”, but all effects are really just effects. When we talk about SSRIs having sexual side effects, this may cash out as them interfering in some way with the horny governor.

There are some extreme circumstances that are almost like knockouts, and may help us distinguish between emotions in similar ways. Our favorite example, of course, is the potato diet. When people eat almost nothing but potatoes for several days, some of them find that the normal sensation of hunger becomes very weird. They say things like:

• “It’s been very easy for me to not eat enough doing this and not realize that’s why I feel off. Might be worth a PSA. Hunger literally feels different on this diet.”
• “finding myself completely forgetting about food, even as something i need to do to live. not experiencing any hunger. no urge to snack. i am certain i’m not drinking enough water. i definitely have more energy, and more focus, despite this … not sure if i’m actually hungry but haven’t eaten nearly enough.”
• “I did get more tired throughout, and my appetite actually continually decreased. Had to remind myself to eat quite often and actually made a schedule.”
• “On 100% potatoes, I don’t ever feel ‘hungry’ the way hunger usually feels, I’ll notice that I’m low-energy or fading, and that’s my signal that I should eat again”
• “the normal feeling of hunger was entirely gone for me – what was left was a feeling of being almost faint and feeling not great when I went too long without eating. Took a lot of adjusting to.”

We think that “hunger” is actually a number of different emotions that come from several different drives. Because eating a well-rounded meal satisfies most of these drives at the same time, we don’t normally experience these emotions independently from one another, which is why we call them by a single name. 

We interpret the comments from the potato diet as reflecting a situation where some hunger emotions are unbundled from others, creating unusual subjective experiences. 

We think it went something like this: let’s say there’s one hunger drive for calories and then a bunch of drives for micronutrients like magnesium, sugar, or whatever. Normally the metabolism governor drives most eating behavior, since that’s the strongest signal. The other signals rise and fall with the signal from the calories governor anyway, because if you’re getting enough calories from a mixed diet, you will be getting approximately the right amount of the other things you need. They only chime in if you happen to be getting a diet really low in magnesium or whatever.

But something about the potato diet convinces your body that its weight set point should be lower, so it starts removing calories from your fat stores instead of adding them. This makes the metabolism governor stay quiet. It doesn’t have to vote for you to eat to get calories anymore, they are being added directly to the bloodstream. 

But your micronutrient governors don’t have the same kinds of reserves, so they keep sending out their error signals as normal. But you’re not used to responding to these micronutrient errors in isolation, and they’re not used to running the show. You feel vaguely weird and bad, but it’s not something you’re used to thinking of as hunger, and you don’t immediately know what to do about it. That’s why it feels weird on the potato diet.

Or here’s a slightly different model: If there are hunger governors for five different things and your diet only provides the nutrients that satisfy four of them, you’ll seem to experience hunger normally: very hungry before meals, full after meals (because of a fullness governor switching on). But there’s one governor that continues to vote for eating, who is later joined by the other four as time passes. So if switching to the potato diet suddenly satisfies all the hunger governors, you might experience the complete satisfaction of your hunger governors for the first time.

Which drives and emotions have been unbundled, and why exactly that would happen on potatoes, remains an open question. 

3.2 Behavioral Exhaustion

You can discover the root of a drive by separating the target of that drive into its component parts, and feeding each one into the system in turn. 

Let’s say you’re craving a cranberry juice cocktail. A natural question might be to wonder why you crave it so bad. Any craving presumably comes from one or more of your drives, but which one(s)?

A reasonable guess is that you don’t crave the whole cranberry juice cocktail, you actually crave one or more of its ingredients. You can test this by consuming the ingredients one at a time. If you first let yourself drink as much water as you want, and you still crave the cranberry juice cocktail, clearly you did not want it just because you were thirsty per se.

So you look at the other ingredients. There’s lots of sugar in the cocktail, maybe you are craving something sweet. So next you eat as much sugar as you want. If you’re still craving the cranberry juice cocktail, then it must have been something else.

In principle you can follow this process as far as you want, to discover precisely the ingredient you were craving. And once you discover the ingredient, you can follow the same process even further. You can go as far as centrifuging the original cranberry juice and eating different strata to determine exactly what part of it you were after. With enough effort, you might be able to identify the exact molecule.

In practice, things probably won’t be so simple. From oral rehydration formula, we know that some combinations of sugar, salt, and water are much more hydrating than others. If you mix the wrong combination, it can even become dehydrating. So in some cases, cravings may be holistic, your drives may really vote for something that is greater than the sum of its parts. This may be why some foods, like beans and rice, are often eaten together and seem much more delicious than the sum of their parts. In our pursuit of a better understanding of psychology, we can’t forget about biology. There is probably a reason why people prefer to drink lemonade instead of consuming water, sugar, and lemon juice in isolation. And by golly, we’re gonna find it.

In general, exhaustion shows that 1) there is a drive for the pure thing being exhausted (or else why would the organism keep taking/doing it), and 2) any behavior remaining after exhaustion cannot be caused in this case by the exhausted drive, though the exhausted drive might also vote for that behavior if it were not exhausted. 

3.3 Fungibility

Another angle is looking at impulses for different actions and trying to determine how they are fungible.

The thermostat only cares about the temperature in the house. When the house is too cold, actions that raise the temperature in any way are all equally successful, since they all correct the thermostat’s error. So from the thermostat’s perspective, actions that raise the house temperature are totally fungible. It is just as happy to turn on the baseboard heating as it is to turn on the forced-air heating, in this absurd hypothetical where your house, for some reason, has both.

We can use other fungible actions in the same way, and trace them back to their common origin. For example, you may notice that you feel hungry. You want bananas. You interrogate that feeling — what else sounds good? The other things that come to mind are avocados, potatoes, and spinach. All of them sound great. 

In many ways these foods are very different — for example, the avocado is high in fat and the banana is not. But you realize that all of the foods that sound good have something in common: they are all high in potassium. So instead of eating any of these foods, you drink some straight potassium chloride in water.

You may find that you no longer feel hungry at all, suggesting that what you thought of as a general sense of hunger was in fact a single drive for potassium. Your potassium governor was happy to fulfill in a number of different ways, so it was willing to vote for bananas, avocado, spinach, anything that would reduce its error. And when you drank straight potassium chloride in water, that also satisfied the drive, so the error signal went away. We don’t know if this would happen, but if it did, that would be fairly strong evidence for a potassium drive. 

Similarly, you might notice you have a craving for eggs and broccoli. Then you eat some nutritional yeast, which is basically nothing but B vitamins. Five minutes later, you don’t crave those foods anymore. Same deal.

3.4 Prevention

A version of fungibility in reverse, or an empirical version of resistance. To see what drive is behind a behavior, keep the person (or animal) from doing the behavior and see what they do instead. If an organism tries to do something, stop it. What does it do instead? This is probably an expression of the same drive. 

If you do this enough, you can triangulate all these behaviors and infer what variable the drive is controlling. You might also learn that two behaviors you thought were different are both expressions of the same drive. 

Also interesting that at some point the organism might do a substitution, e.g. look at pictures of food if it can’t manage to eat. When they can’t substitute, you have the drive surrounded. 

3.5 Effort

A similar method is to see what goals an animal will expend large amounts of effort to reach. A rat will push a lever 1000 times for water if that’s its only way to get hydration. It wouldn’t do this if the desire for water were an epiphenomenon of some other drive. The rat really wants water, specifically wants water, and will accept no substitutes. The fact that it puts in so much effort is the evidence.

3.6 Division

To alchemists, Fire was considered “the true and Universal Analyzer of all Mixt Bodies”, capable of dividing any substance into its more base components. 

But there were some problems with this approach. The alchemists were shaken when they discovered that Fire was not the only thing that could divide a substance into simpler components. They found that liquids like urine, beer, and wine would separate when put out in extreme cold.

Worse, there were some elements that fire couldn’t separate at all. Robert Boyle relates a story of gold being kept in a furnace for two months straight. The gold stayed a liquid the whole time, but it never separated into baser substances. Apparently fire had failed to separate gold into its elementary ingredients. Some true and Universal Analyzer! Or, more radically, maybe this meant that gold didn’t have more basic components, that gold itself was an element.

Observations like these threw alchemy into a state of chaos. In the preface to his Elements of Chemistry, where he pitches his homies on a new way of doing things, Antoine Lavoisier explains this history. He apologizes for not including a list of all the elements, saying (emphasis ours):

It will, no doubt, be a matter of surprise, that in a treatise upon the elements of chemistry, there should be no chapter on the constituent and elementary parts of matter; but I shall take occasion, in this place, to remark, that the fondness for reducing all the bodies in nature to three or four elements, proceeds from a prejudice which has descended to us from the Greek Philosophers. The notion of four elements, which, by the variety of their proportions, compose all the known substances in nature, is a mere hypothesis, assumed long before the first principles of experimental philosophy or of chemistry had any existence. In those days, without possessing facts, they framed systems; while we, who have collected facts, seem determined to reject them, when they do not agree with our prejudices. The authority of these fathers of human philosophy still carry great weight, and there is reason to fear that it will even bear hard upon generations yet to come.

It is very remarkable, that, notwithstanding of the number of philosophical chemists who have supported the doctrine of the four elements, there is not one who has not been led by the evidence of facts to admit a greater number of elements into their theory. The first chemists that wrote after the revival of letters, considered sulphur and salt as elementary substances entering into the composition of a great number of substances; hence, instead of four, they admitted the existence of six elements. Beccher assumes the existence of three kinds of earth, from the combination of which, in different proportions, he supposed all the varieties of metallic substances to be produced. Stahl gave a new modification to this system; and succeeding chemists have taken the liberty to make or to imagine changes and additions of a similar nature. All these chemists were carried along by the influence of the genius of the age in which they lived, which contented itself with assertions without proofs; or, at least, often admitted as proofs the slighted degrees of probability, unsupported by that strictly rigorous analysis required by modern philosophy.

Lavosier doesn’t claim that he knows what is an element and what is not. He says that we are going to need some very serious analysis before any of us can be sure. So instead of starting with a list of the elements, Lavoisier proposes a new method for figuring them out:

If, by the term elements, we mean to express those simple and indivisible atoms of which matter is composed, it is extremely probable we know nothing at all about them; but, if we apply the term elements, or principles of bodies, to express our idea of the last point which analysis is capable of reaching, we must admit, as elements, all the substances into which we are capable, by any means, to reduce bodies by decomposition. Not that we are entitled to affirm, that these substances we consider as simple may not be compounded of two, or even of a greater number of principles; but, since these principles cannot be separated, or rather since we have not hitherto discovered the means of separating them, they act with regard to us as simple substances, and we ought never to suppose them compounded until experiment and observation has proved them to be so.

To put this in more modern language: What we mean by “element” is “something that can’t be divided”. If we’ve discovered a way to divide some substance into different components, that substance can’t be an element. Elements are by definition the basic building blocks of matter that cannot be divided — so if it can be divided in any way, it’s not an element. (Ignore atomic chemistry for the moment, they wouldn’t discover that for a hundred years.)

Substances that we can’t divide are candidates. They might be elements — after all, they seem entirely indivisible so far. But some day we might discover a way to divide them into different components, which would prove they’re not elements after all. So they’re not elements for sure, only candidates.

If you put wood into a fire, it will be divided into ashes, smoke, etc. This makes it pretty clear that wood isn’t an element. But as of 1789, no one has found a way to divide gold into anything else, and it’s not for lack of trying. So gold should be considered an element, at least for now. To Lavoisier, gold is provisionally an element. Other things can be divided in a way that yields gold, but he’s never been able to confirm a way to divide gold into anything simpler. 

In short, it’s impossible to prove that something is an element, but you can prove that something is not, simply by dividing it. Anything we know how to divide is proven to be a compound, not an element. But anything we don’t know how to divide is only a possible element, because we may yet discover some way to divide it. 

We find ourselves in a similar situation today, and we can use something like Lavoisier’s approach to discover the full set of psychological drives (each with a corresponding emotion and governor), just like the chemists used his approach to discover the full set of elements.

The difference between these methods and the methods from the previous sections is that the methods in the previous sections start with observed behaviors, and try to figure out what drive(s) are behind them. These methods start with established or proposed drive(s) and try to learn more.

A good place to start is hunger. We think that hunger is not one emotion, it’s a common term applied to many emotions. The reason these signals are all mistakenly called by the same name, at least in English, is that they all come from governors that vote for eating behavior. These behaviors all look superficially similar, but in fact we put things in our mouths for a variety of reasons.  

Humans come with several different hunger drives because we need to eat several different things to remain healthy. We’ll call these things-you-need-to-eat “nutrients”, though this may be a little different from the common usage of that word.

Most foods contain more than one nutrient, so most foods satisfy more than one governor. A decent burrito will satisfy almost everything — your salt, carbs, fat, and guacamole governors, etc. This makes these emotions hard to disentangle, so most cultures don’t bother. It’s still possible to express these drives — “I’m really craving pickles” or “I would kill for some mozzarella right now” — and there are some related idioms like “sweet tooth”. But we don’t have dedicated words for each individual emotion, we just lump them together as “hunger”.

If you’ve messed around with your diet in really strange ways, as we have, you can sometimes get to the point where the different hunger drives become obvious. When we supplemented potassium, it was very clear to us that this increased our cravings for salt.

Like Lavoisier, we can try to break hunger down into individual drives, until we find drives we can’t distinguish any further. Those drives that can’t be divided are probably basic drives, at least until proven otherwise.

Let’s play through some examples. We think that there is probably at least one drive for salt (likely for sodium, but maybe there is a drive for chloride too) and at least one drive for fatty foods.

Now consider Joey, who wants to eat a pile of onion rings. If this is simply unalloyed hunger, a general desire for calories, then if you give Joey any other food, and he eats that food to exhaustion, he should no longer want to eat the onion rings.

However, if we assume there is one drive for salty foods, and a separate drive for fatty foods, we might suspect that the strong desire for onion rings reflects a combination of these desires, leading him to seek a food that is both salty and fatty. If true, he will also be at least somewhat interested in foods that are salty but not fatty, and in foods that are fatty but not salty.

Then, if we let Joey eat as much as he wants of a food that is salty but not fatty (perhaps mini pretzels), he will still be interested in foods that are fatty but not salty. And if we let him eat as much as he wants of a food that is fatty but not salty (perhaps avocado), he will still be interested in foods that are salty but not fatty. This would demonstrate that these are different drives. 

It probably has not escaped your attention that most foods that are salty are also fatty, and vice versa (french fries, olives, peanut butter, etc.). Perhaps this indicates some kind of drive specifically for foods that are both fatty and salty, a drive that cannot be extinguished by salt or fat in isolation. We will probably discover some outcomes at least this weird, and we should try not to stick too closely to any assumptions. The early chemists really didn’t expect to some day discover isotopes.

Evolution is doing her own thing, and she has no obligation to provide categories that make any sense to us. Governors might be controlling anything at all. There might be an important hunger governor that controls a proxy of a proxy of the ratio between sodium and potassium in the bloodstream. That’s not something that a human will find intuitive — but it’s not about being intuitive to the humans! The only law is, whatever works! 

But assuming for a moment that our study with Joey did support the idea that there’s both a salt governor and a fat governor, similar techniques could be used to discover whether there’s just one governor controlling fat-hunger, or if there are separate drives for different kinds of fat. Perhaps one drive for saturated and another drive for unsaturated fat. Or perhaps one drive for sterols? The truth will probably be stranger than we expect. 

A relatable example of this is the “dessert stomach”. If you can eat a big meal and still have room for dessert, it must be because your sugar or fat governor (or both) is still active. You can exhaust chicken-hunger while not exhausting chocolate-lava-cake hunger. This is clear evidence that there are at least two hunger drives.

3.7 The Parable of Rat C13

A lot of the studies we’ve suggested would be difficult or unethical to run on humans. But it may be easier to run this kind of study with animals. 

First of all, we can have more control over an animal’s diet than we usually would over a human’s. And second, humans might try to eat more or less of something to show the researchers how virtuous or how tough they are, but animals won’t have anything to prove — they’ll express their hunger drives with little interference from drives about impressing the research team. 

A design might look something like this: Restrict the animal’s food for a while so we know it will be hungry. Then, give it as much butter as it wants and let it eat until it stops eating. This way, we can assume that it should be fully corrected for any nutrient in the butter. 

Then, give the animal access to olive oil. If it eats an appreciable amount of olive oil, that suggests there’s a drive for at least one nutrient in olive oil that is not in butter. Further tests should be able to isolate the exact nutrients. You could also try this in the opposite order, to find if there are drives for nutrients in butter that are not found in olive oil. 

And in fact, some of these studies have already been run on animals. As one example, consider one 1968 paper by Paul Rozin. In this study, Rozin housed Sprague-Dawley rats in cages that contained water, a salt-vitamin mix, and a “liquid cafeteria” of three foods: 1) sucrose in water, 2) a 30% protein solution, and 3) Mazola oil for fat. All the rats responded well to this cafeteria, growing bigger and showing a lot of stability in their choices of liquids.

Rats clearly had protein targets and were able to hit them without blinking. When offered protein solution diluted by ½ or ¼, they increased how much solution they drank to compensate, so that their protein intake was approximately constant, though they didn’t compensate quite as well for the ¼ solution as they did for the ½ solution. Some rats were better than others at keeping their protein intake constant. This starts looking like an early form of cybernetic personality testing — at least in rats. 

Even when Rozin added quinine hydrochloride to the diluted solution, a flavor that rats normally hate, they still compensated and drank more of the diluted protein solution. This suggests they really were controlling protein intake, not just drinking for taste. That said, Rat C13 seemed to like the quinine just fine, and didn’t show any preference for the solution without it. Another sign of personality — that Rat C13, what a character!

In contrast, when Rozin diluted the sucrose solution, their source of carbohydrates, the rats only drank a little more sucrose solution to compensate. Some rats didn’t drink more sucrose solution at all. This is kind of surprising, because under normal circumstances all the rats took at least 50% of their calories from sucrose. 

Similarly, when rats were deprived of protein for a few days, they would drink more protein solution to make up for it. But when rats were deprived of sucrose solution for a few days, they would actually drink slightly less sucrose solution when it came back. The effects of being deprived were also noticeably different. Rats lost more than twice as much weight when deprived of protein than when deprived of carbohydrates.

We wish that we could provide similar comparisons for fat, but Rozin says that, “due to the very low levels of fat intake, no meaningful compensation value could be calculated.”

This isn’t evidence that carbohydrates are totally unregulated — they may just be regulated on a timescale that isn’t noticeable over a few days. The author speculates that, “this failure may have occurred because the highly palatable 35% sucrose solution is consumed at levels well above a physiological minimum.” And of course, the regulation may just be too complex to see in Rozin’s data. But it does at least look like evidence that protein is closely controlled, and controlled separately from overall calorie intake, at least in rats. 

Score one for Lavoisier’s method. Assuming that these findings are reliable, this seems like clear evidence against the idea that there is just one elemental drive for hunger. It also seems like evidence in favor of a drive for protein. Whether that drive for protein is elemental, or whether it too can be broken down into a collection of more basic drives, perhaps drives for individual amino acids, remains to be seen. 

Similar studies have suggested that cows have something like 16 different hunger drives: 

The idea of feeding minerals “free choice” to livestock came about by a need to decrease over-consumption of a liquid supplement containing phosphoric acid, protein, molasses, and other minerals. Upon investigation, it was found that the liquid supplement was being used heavily by the animal as a source of phosphorous. Consequently, we discovered if animals had access to a phosphorous source on a free choice basis, over-consumption of the liquid ceased. We then extended this concept to other vitamins and minerals: if the animal was able to select phosphorous on a free choice basis, perhaps calcium could be selected in the same manner – success!

…In time, potassium, sulfur, silicon, magnesium, vitamins, and trace minerals were added to the list. Finally, there were 16 separate vitamins and minerals fed free choice.

These findings should be independently and widely replicated before we treat them as strong evidence, but if true, this suggests that cows have drives for each of these vitamins and minerals. If they didn’t have a drive for sulfur, why would they spend their time eating it? 

4. In Which We Speculate About What Emotions There Are

The first major achievement for psychology may be a complete list of all the drives, governors, and emotions — each drive comes from a governor, and the emotion is that governor’s error signal. The most obvious analogy is to chemistry. This will be our version of the periodic table. 

We’re still a long way off from this list being completed, but we can make some educated guesses about what will be on there once it’s finished. You just heard a lot of those guesses in the previous sections — now, we’ll put those guesses together into a rough draft. 

For now, we’ll try to call each governor by the name of its error signal — drives to eat come from a governor whose error is hunger, so these are hunger governors. The drive to keep yourself from physical harm comes from a governor whose error is pain, so this is the pain governor. 

That said, there are a few cases where it’s easier to call a governor by some other name. It’s nice when we have existing terms like “thirst” already on hand, but there are some emotions that don’t have a common name, at least not in English. So sometimes we will punt and call these drives only “a drive to do X”, where X is the characteristic behavior that makes us suspect there’s a drive there in the first place. 

The big question at this point is whether this can be more than just a list. The chemical elements have a periodic structure, their properties repeat in a regular pattern. This repetition, or periodicity, is visually organized in the periodic table, where elements are grouped into rows and columns to highlight these patterns. That’s the whole reason to have the periodic table in the first place — it’s more than just a list, and it eventually led to a better understanding of how the properties of elements are related to their atomic structure. 

Maybe there is no structure or pattern to the drives, and we will just end up with a long list. But if there’s any kind of pattern or structure, we’d love to come up with an organization that highlights that structure, instead of just listing the drives one by one. 

To make an early attempt, for now we will group the drives in three categories: physiological emotions, that attend to the basics needed to keep the body functioning; environmental emotions, that attend to the qualities of a person’s immediate external environment; and social emotions, that attend to a person’s social status and relations. 

• Physiological
  • Suffocation/Panic
  • Pain
  • Hot
  • Cold
  • Exhaustion
  • Waking
  • Thirst
  • Hunger (actually several drives)
  • Satiety (stops us from eating; also probably several drives)
  • A drive to fidget and be active that burns excess calories
  • “Zoomies” (this may be the same as the drive to fidget; consider also that rodents need wheels in their cages, and if you give them a wheel in the wild, they’ll run on that too!)
  • Horny
  • A drive to pee (The Sims called it “Bladder”)
  • A drive to shit
• Environmental
  • Fear
  • Disgust
  • A drive to have a clean and organized living space (The Sims called it “Room”)
  • A drive to have a clean and well-groomed body
  • Possibly decorative drives (though these may be extension of cleanliness drives)
  • Possibly a drive to dig
  • Possibly a drive to look at animals
  • Possibly a drive to collect or hoard
  • Possibly a drive to sort
• Social
  • A drive to regulate social status up
  • A drive to keep social status from growing too fast
  • A drive for physical contact; “touch starved”
  • A drive for privacy, perhaps territorial
  • A drive for autonomy
  • A drive to socially dominate
  • Possibly a desire to follow or submit 
  • Self-consciousness (an error when you are not acting consistently or normatively)
  • Empathy
  • Grief (the drive is to care for others, but the error signal is grief)
  • Loneliness
  • Anger
  • Shame

The list should also include other signals that are not cybernetic control errors. Here’s our current best guess for that list: 

• Happiness
• Surprise
• Curiosity

Happiness and surprise are two things we subjectively experience all the time, but they don’t seem to be cybernetic control errors. They also don’t seem to drive behavior. 

In contrast, curiosity doesn’t seem to be a cybernetic control error, because it doesn’t seem to drive a target to zero, but curiosity does seem to drive behavior. As we speculated above, we think curiosity may be an adversarial signal that teaches us about the world by voting for us to explore options that our governors wouldn’t vote for on their own. 

If the history of psychology is any indication, people will want to jump straight to figuring out the social emotions. We think this is a mistake. The social emotions will probably be the hardest to uncover.

There are two reasons to leave the social emotions for later.

First, we don’t know what the social emotions might be controlling. If there really is a dominance emotion, what is it targeting? It can’t literally be “the image of someone wailing at your feet.” It’s going to be something more subtle, and we don’t currently know how to capture or measure that thing.

Second, investigating the social emotions is impractical. If you want to be able to alter someone’s social status at will for an experiment, you kinda have to put people in a Biodome or a VR world. Even then, it’s hard to be sure you’re really evoking what goes on in the regular world.

We have much stronger suspicions about what the physiological drives control, and investigating them doesn’t require us to build a whole alternative society. You can just make people eat salt or not eat salt and see what happens. 

And because other animals probably share a lot of our physiological emotions, we can run studies on them that would be unethical or impractical to run on humans. You can’t study the social emotions in other animals because other animals probably don’t have most of the social emotions that humans do. Maybe dolphins or elephants, but they’re hard to study.

We should start with something easier. We should start by studying emotions like hunger and fatigue, then use what we’ve learned to eventually understand the social emotions.

In chemistry, we discovered the gases first, then later got around to the other elements. In psychology, we will probably learn about the physiological drives first. We may cut our teeth on hunger before working up to things like fatigue, pain, fear, and eventually the social emotions, which are probably the most baroque and complex. 

It’s true that the social drives are the most interesting, and it might seem like understanding the social drives might be more important, might solve more of the problems you care about. But be patient. You have to spend some time rolling balls down ramps before you can go to the moon.

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[Next: MORE METHODS]

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