Time Preference: the most under-appreciated mental trait

Time Preference isn’t sexy and exciting, like anything related to, well, sex. It isn’t controversial like IQ and gender. In fact, most of the ink spilled on the subject isn’t even found in evolutionary or evolutionary psychology texts, but over in economics papers about things like interest rates that no one but economists would want to read.

So why do I think Time Preference is so important?

Because I think Low Time Preference is the true root of high intelligence.

First, what is Time Preference?

Time Preference (aka future time orientation, time discounting, delay discounting, temporal discounting,) is the degree to which you value having a particular item today versus having it tomorrow. “High time preference” means you want things right now, whereas “low time preference” means you’re willing to wait.

A relatively famous test of Time Preference is to offer a child a cookie right now, but tell them they can have two cookies if they wait 10 minutes. Some children take the cookie right now, some wait ten minutes, and some try to wait ten minutes but succumb to the cookie right now about halfway through.

Obviously, many factors can influence your Time Preference–if you haven’t eaten in several days, for example, you’ll probably not only eat the cookie right away, but also start punching me until I give you the second cookie. If you don’t like cookies, you won’t have any trouble waiting for another, but you won’t have much to do with it. Etc. But all these things held equal, your basic inclination toward high or low time preference is probably biological–and by “biological,” I mean, “mostly genetic.”

Luckily for us, scientists have actually discovered where to break your brain to destroy your Time Preference, which means we can figure out how it works.

The scientists train rats to touch pictures with their noses in return for sugar cubes. Picture A gives them one cube right away, while picture B gives them more cubes after a delay. If the delay is too long or the reward too small, the rats just take the one cube right away. But there’s a sweet spot–apparently 4 cubes after a short wait—where the rats will figure it’s worth their while to tap picture B instead of picture A.

But if you snip the connection between the rats’ hippocampi and nucleus accumbenses, suddenly they lose all ability to wait for sugar cubes and just eat their sugar cubes right now, like a pack of golden retrievers in a room full of squeaky toys. They become completely unable to wait for the better payout of four sugar cubes, no matter how much they might want to.

So we know that this connection between the hippocampus and the nucleus accumbens is vitally important to your Time Orientation, though I don’t know what other modifications, such as low hippocampal volume or low nucleus accumbens would do.

So what do the hippocampus and nucleus accumbens do?

According to the Wikipedia, the hippocampus plays an important part in inhibition, memory, and spatial orientation. People with damaged hippocampi become amnesiacs, unable to form new memories.There is a pretty direct relationship between hippocampus size and memory, as documented primarily in old people:

“There is, however, a reliable relationship between the size of the hippocampus and memory performance — meaning that not all elderly people show hippocampal shrinkage, but those who do tend to perform less well on some memory tasks.[71] There are also reports that memory tasks tend to produce less hippocampal activation in elderly than in young subjects.[71] Furthermore, a randomized-control study published in 2011 found that aerobic exercise could increase the size of the hippocampus in adults aged 55 to 80 and also improve spatial memory.” (wikipedia)

Amnesiacs (and Alzheimer’s patients) also get lost a lot, which seems like a perfectly natural side effect of not being able to remember where you are, except that rat experiments show something even more interesting: specific cells that light up as the rats move around, encoding data about where they are.

“Neural activity sampled from 30 to 40 randomly chosen place cells carries enough information to allow a rat’s location to be reconstructed with high confidence.” (wikipedia)

"Spatial firing patterns of 8 place cells recorded from the CA1 layer of a rat. The rat ran back and forth along an elevated track, stopping at each end to eat a small food reward. Dots indicate positions where action potentials were recorded, with color indicating which neuron emitted that action potential." (from Wikipedia)
“Spatial firing patterns of 8 place cells recorded from the CA1 layer of a rat. The rat ran back and forth along an elevated track, stopping at each end to eat a small food reward. Dots indicate positions where action potentials were recorded, with color indicating which neuron emitted that action potential.” (from Wikipedia)

According to Wikipedia, the Inhibition function theory is a little older, but seems like a perfectly reasonable theory to me.

“[Inhibition function theory] derived much of its justification from two observations: first, that animals with hippocampal damage tend to be hyperactive; second, that animals with hippocampal damage often have difficulty learning to inhibit responses that they have previously been taught, especially if the response requires remaining quiet as in a passive avoidance test.”

This is, of course, exactly what the scientists found when they separated the rats’ hippocampi from their nucleus accumbenses–they lost all ability to inhibit their impulses in order to delay gratification, even for a better payout.

In other word, the hippocampus lets you learn, process the moment of objects through space (spatial reasoning) and helps you suppress your inhibitions–that is, it is directly involved in IQ and Time Preference.


So what is the Nucleus Accumbens?

According to Wikipedia:

“As a whole, the nucleus accumbens has a significant role in the cognitive processing of aversion, motivation, pleasure, reward and reinforcement learning;[5][6][7] hence, it has a significant role in addiction.[6][7] It plays a lesser role in processing fear (a form of aversion), impulsivity, and the placebo effect.[8][9][10] It is involved in the encoding of new motor programs as well.[6]

Dopaminergic input from the VTA modulate the activity of neurons within the nucleus accumbens. These neurons are activated directly or indirectly by euphoriant drugs (e.g., amphetamine, opiates, etc.) and by participating in rewarding experiences (e.g., sex, music, exercise, etc.).[11][12] …

The shell of the nucleus accumbens is involved in the cognitive processing of motivational salience (wanting) as well as reward perception and positive reinforcement effects.[6] Particularly important are the effects of drug and naturally rewarding stimuli on the NAc shell because these effects are related to addiction.[6] Addictive drugs have a larger effect on dopamine release in the shell than in the core.[6] The specific subset of ventral tegmental area projection neurons that synapse onto the D1-type medium spiny neurons in the shell are responsible for the immediate perception of the rewarding property of a stimulus (e.g., drug reward).[3][4] …

The nucleus accumbens core is involved in the cognitive processing of motor function related to reward and reinforcement.[6] Specifically, the core encodes new motor programs which facilitate the acquisition of a given reward in the future.[6]

So it sounds to me like the point of the nucleus accumbens is to learn “That was awesome! Let’s do it again!” or “That was bad! Let’s not do it again!”

Together, the nucleus accumbens + hippocampus can learn “4 sugar cubes in a few seconds is way better than 1 sugar cube right now.” Apart, the nucleus accumbens just says, “Sugar cubes! Sugar cubes! Sugar cubes!” and jams the lever that says “Sugar cube right now!” and there is nothing the hippocampus can do about it.


What distinguishes humans from all other animals? Our big brains, intellects, or impressive vocabularies?

It is our ability to acquire new knowledge and use it to plan and build complex, multi-generational societies.

Ants and bees live in complex societies, but they do not plan them. Monkeys, dolphins, squirrels, and even rats can plan for the future, but only humans plan and build cities.

Even the hunter-gatherer must plan for the future; a small tendril only a few inches high is noted during the wet season, then returned to in the dry, when it is little more than a withered stem, and the water-storing root beneath it harvested. The farmer facing winter stores up grain and wood; the city engineer plans a water and sewer system large enough to handle the next hundred years’ projected growth.

All of these activities require the interaction between the hippocampus and nucleus accumbens. The nucleus accumbens tells us that water is good, grain is tasty, fire is warm, and that clean drinking water and flushable toilets are awesome. The hippocampus reminds us that the dry season is coming, and so we should save–and remember–that root until we need it. It reminds us that we will be cold and hungry in winter if we don’t save our grain and spend a hours and hours chopping wood right now. It reminds us that not only is it good to organize the city so that everyone can have clean drinking water and flushable toilets right now, but that we should also make sure the system will keep working even as new people enter the city over time.

Disconnect these two, and your ability to plan goes down the drain. You eat all of your roots now, devour your seed corn, refuse to chop wood, and say, well, yes, running water would be nice, but that would require so much planning.


As I have mentioned before, I think Europeans (and probably a few other groups whose history I’m just not as familiar with and so I cannot comment on) IQ increased quite a bit in the past thousand years or so, and not just because the Catholic Church banned cousin marriage. During this time, manorialism became a big deal throughout Western Europe, and the people who exhibited good impulse control, worked hard, delayed gratification, and were able to accurately calculate the long-term effects of their actions tended to succeed (that is, have lots of children) and pass on their clever traits to their children. I suspect that selective pressure for “be a good manorial employee” was particularly strong in German, (and possibly Japan, now that I think about it,) resulting in the Germanic rigidity that makes them such good engineers.

Nothing in the manorial environment directly selected for engineering ability, higher math, large vocabularies, or really anything that we mean when we normally talk about IQ. But I do expect manorial life to select for those who could control their impulses and plan for the future, resulting in a run-away effect of increasingly clever people constructing increasingly complex societies in which people had to be increasingly good at dealing with complexity and planning to survive.

Ultimately, I see pure mathematical ability as a side effect of being able to accurately predict the effects of one’s actions and plan for the future (eg, “It will be an extra long winter, so I will need extra bushels of corn,”) and the ability to plan for the future as a side effect of being able to accurately represent the path of objects through space and remember lessons one has learned. All of these things, ultimately, are the same operations, just oriented differently through the space-time continuum.

Since your brain is, of course, built from the same DNA code as the rest of you, we would expect brain functions to have some amount of genetic heritablity, which is exactly what we find:

Source: The Heritability of Impulse Control
Source: The Heritability of Impulse Control, Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies

“A meta-analysis of twin, family and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on impulsivity. The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity. Age, sex, and study design (twin vs. adoption) were all significant moderators of the magnitude of genetic and environmental influences on impulsivity. The relative contribution of genetic effects (broad sense heritability) and unique environmental effects were also found to be important throughout development from childhood to adulthood. Total genetic effects were found to be important for all ages, but appeared to be strongest in children. Analyses also demonstrated that genetic effects appeared to be stronger in males than in females.”


“Shared environmental effects” in a study like this means “the environment you and your siblings grew up in, like your household and school.” In this case, shared effects were unimportant–that means that parenting had no effect on the impulsivity of adopted children raised together in the same household. Non-shared environmental influences are basically random–you bumped your head as a kid, your mom drank during pregnancy, you were really hungry or pissed off during the test, etc., and maybe even cultural norms.

So your ability to plan for the future appears to be part genetic, and part random luck.


Bi-modal brains?

But... the second equation makes perfect sense.
But… the second equation makes sense.

So I have this co-woker–we’ll call her Delta. (Certain details have been changed to protect the privacy of the innocent.) Delta is an obviously competent, skilled worker who has succeeded at her job in a somewhat technical field for many years. She has multiple non-humanities degrees or accredidations. And yet, she frequently says things that are mind-numbingly dumb and make me want to bang my head on my desk.

To be fair, everybody makes mistakes and says incorrect things sometimes; maybe she thinks the exact same thing about me. Also, I have no real perspective on how dumb people think, because I haven’t spent much of my life talking to them. Even the formerly homeless people I know can carry on a layman’s discussion of quantum physics.

At any rate, I don’t actually think Delta is dumb. Instead, I think she has, essentially, two brain modes: Feeling Mode and Logic Mode.

Feeling Mode happens to be her default; she can do Logic Mode perfectly well, but she has to concentrate to activate it. If Logic Mode isn’t on, then things just get automatically processed through Feelings Mode and, as a result, don’t always make sense.

When Logic Mode is on, she does quite fine–her career, after all, is dependent on her rational, logical abilities, above-average math skills, etc. But her job is just that, not a passion, not something she’d do if it didn’t put food on the table. When she is in default mode, her brain just doesn’t make logical connections, notice patterns (especially meta-patterns), or otherwise understand a lot of the stuff going on around her. And her inability to judge distances/estimate sizes just makes me cringe.

My conversation topics typically go over like lead balloons.

In a recent Stanford Magazine article, Content to Code? in which Marissa Messina discusses her decision to major in computer science:

BEFORE STANFORD, I’d never heard the term “CS.” When my pre-Orientation mates used it repeatedly during our technology-free week of hiking in Yosemite prior to the start of freshman year, I had to ask them what it stood for. But their matter-of-fact response—”computer science”—was still a foreign concept to me. …

“Nonetheless, I celebrate my decision to develop my technical side. Although it does not come naturally to me, in Bay Area culture, knowing how to code feels like a prerequisite to existing. …

“I quickly learned through get-to-know-you conversations that being a “techie” was inherently cooler than being a “fuzzie,” and that social standard plus rumors of superior job prospects for engineers began to make me question my plan to major in psychology.

“Three years later, here I am, close to graduating and capable of coding. Now what?

“I certainly don’t imagine myself thriving as a professional programmer, because thinking in syntactically flawless computer-speak remains a wearisome process for me. … “

How on Earth does anyone arrive at Stanford without knowing that computer science exists?

Messina illustrates my theory rather well. She can go into logic mode, she can write code well enough to major in CS at Stanford, but it does not come naturally to her and she finds it rather unpleasant. She is only doing it because, back in freshman year, someone said her job prospects would be better with a CS degree. Now she realizes that she doesn’t actually want to do CS for a full-time job.

I suspect that most people operate primarily in Feelings Mode, and may be even worse than my co-worker at activating Logic Mode. Some may not have an operative Logic Mode at all; a few people may not have a Feeling Mode, but that seems less common. Feelings are instinctual, irrational, and messy. They exist because they are useful, but that does not mean they make logical sense.

For example, let’s suppose an out-of-control train is racing toward a group of schoolchildren who’ve been tied to the railroad tracks, but if you push a 9-foot tall man in heavy plate mail in front of the train, his death will save the children.

People operating in Logic Mode start debating the virtues of Kant’s Categorical Imperative verses Mill’s Utilitarianism.

People operating in Feelings Mode want to know what kind of psycho came up with a fucked up question like that. Children tied to the train tracks? Murdering an innocent bystander by pushing him in front of the train? Why are you fuckers debating this? Are you all sick in the head?

When Feeling people switch over into Logic Mode, I suspect it exerts some cost on them: that is, they can do it, but they don’t really like it. It’s uncomfortable, unpleasant, and sometimes exhausting. So most of the time, they prefer to be in default mode.

So there are things that they can understand in Logic Mode, but since they find the whole business unpleasant, they prefer to ignore such conclusions if they possibly can. This probably makes it very difficult to get people to make any kind of decisions involving unpleasant scenarios + data. The unpleasantness itself of the scenario breaks them out of Logic Mode and into Feeling Mode, and then the whole business is flushed down the toilet because someone goes into a screaming fit because you hurt their feelings with your data.

Earlier this morning, I happened across this “Systematizing Quotient” Quiz that HBD Chick linked to. Obviously the quiz has certain drawbacks, like user bias and the difficulty of comparing oneself to others (do I know more or less about car engines than other people? I probably know less about them than most men, but since I can diagram how an engine works and explain it, do I know more than the average woman? Where do I fall on a population scale? And what if I wouldn’t research something before buying it because I already know all about it, or because I think the brands available on the market are similar enough that the time spent resourcing would not be cost-effective?) but I thought I’d try it, anyway.

I scored in the 61-80 range, which is not terribly surprising. What’s weird is just how low everyone else scores, since the averages are 24 and 30 for women and men, respectively, and it’s not like the scale goes down to -50 or anything.

At any rate, when Delta started talking about how much she hates the Common Core math, well, I was curious. I did some digging and came up with problems like the one at the top of the screen, generally accompanied by a bunch of comments from parents like, “What are they even doing?” and “I have no idea what that is!” and “That makes no sense!” And I just look at them all like, Wow, you can’t figure out that 5+2+10+10+10=37?

Sure, math is a recently evolved trait and all, but those sorts of comments still vaguely surprise me.

IQ probably intersects the two modes via a separate axis. That is, a high-IQ Feelings Person might be able to concentrate enough of their mental resources to out-math a low-IQ Logic person, and vice versa, a high-IQ Logic Person might be able to concentrate enough mental resources to out-feel a Feeling Person. (For example, by reading a book about what various facial expressions mean and then using that knowledge in real life.) Delta, for example, could probably figure out the problem after a while, but would still say it’s a terrible problem.

There was a conversation around here somewhere about a recent paper that came out claiming that the discrepancy between the number of men and women in high-end mathematics was due to not enough girls taking rigorous math courses in middle school. Well, I don’t know about the middle schools where the paper was published, but my middle school only had one math class, and we all took it, so I don’t think that’s exactly the problem. More likely, cognitive differences just happen to be manifesting themselves in Middle School, and the math geniuses are starting to outshine people who are smart and hard working but not geniuses.

In the conversation, someone remarked that while women (or in this case, girls,) they’ve known can do math perfectly well, they tend not to enjoy it, and prefer doing other things, whereas the men they know are more or less forced to do it because their brains just happen to automatically look for patterns. This was the original inspiration for this post; the idea that someone might be able to switch back and forth between two modes, but would generally prefer one, while someone else might generally prefer the other. I might call it “Logic Mode” and The Guardian might call it “Systematizing Mode”, but they’re both basically the same.

If this is true, most people may not operate in Feeling Mode, but most women do. On the other hand, it may be that only a small sub-set of men operate primarily in Logic Mode, either, but they happen to be a larger sub-set than the sub-set of women who operate primarily in Logic Mode. Since I don’t talk to most people (no one possibly could,) and my real-life conversations are largely limited to other women, I am curious about your personal observations.