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Check this out. Five numbers appear on a screen in different locations. They remain visible for 210 milliseconds and then they are obscured. The subject must then touch the locations in increasing order of the numbers that appeared there. That’s pretty much impossible. Here’s a human subject who is highly trained and does an impressive job but still fails miserably.
Now check out how nonchalantly this chimpanzee does it.
I didn’t even know they could count. Note that the 5 numbers are random integers between 1 and 9. So the chimp is processing a binary relation in short-term memory, not to mention reading at a super-human rate. There are more videos here. I saw these at Colin Camerer’s talk last week at Arthur Robson‘s conference on the Biological Basis of Preferences.
Over the weekend I attended a conference at the University of Chicago on The Biological Basis of Preferences and Behavior, and Balazs Szentes stole the show with a new theory of the peacock’s tail. In Balazs’ theory a world without large and colorful peacock plumage is simply not stable.
A large tail is an evolutionary disadvantage: it serves no useful purpose and it slows down the male and makes him conspicuous to predators. So why do genes for large tails appear and take over the population of male peacocks? Balazs’ answer is based on matching frictions in the peacock mating market. Suppose female peacocks choose which type of male peacock to mate with: small or large tails. Once the females sort themselves across these two separate markets, the peacocks are matched and they mate.
The female peacocks are differentiated by health, and within a peacock couple health partially compensates for the disadvantageous tail. In the model this means that healthy females who mate with big-tailed peacocks will produce almost as many surviving offspring as they would if they mated with peacocks without the disadvantage of the tail.
This substitution between the characteristics of female and male peacocks creates a selection effect in the mating market. Consider what happens when a small-tailed peacock population is invaded by a mutation which gives some male peacocks large tails. Since female peacocks make up half the population of peacocks there is now an imbalance in the market for small-tailed peacocks. In particular the males are in excess demand and some females will have trouble finding a mate.
On the other hand the big-tailed male peacocks are there for the taking and its going to be the healthy female peacocks who will have the greatest incentive to switch to the market for big tail. The small cost they pay in terms of reduced quantity of offspring will be offset by their increased chance of mating. The big tails have successfully invaded.
Once they have taken over the population (Balasz shows that under his conditions there is no equilibrium with two kinds of male peacocks) he same selection effect prevents small tails from invading. When a small-tail mutation appears all the females will want to mate with them. The market for small tail gets flooded with eager females up to the point where some of them are going to have a hard time finding a mate. Given this, each female must decide whether to take a gamble and try to mate with the small-tail male or have a sure chance of mating with a large tail.
The unhealthy females are going to be the ones who are most willing to take the risk because they are the least compatible with the large-tail males. This means that the small-tail mutants can only mate with unhealthy females and (under the conditions Balazs identifies) this more than offsets their advantage, they produce fewer offspring than the large-tails and they are driven out of the population.
The human eye color blue reflects a simple, predictable, and reliable genetic mechanism of inheritance. Blue-eyed individuals represent a unique condition, as in their case there is always direct concordance between the genotype and phenotype. On the other hand, heterozygous brown-eyed individuals carry an allele that is not concor- dant with the observed eye color. Hence, eye color can provide a highly visible and salient cue to the child’s heredity. If men choose women with characteristics that promote the assurance of paternity, then blue-eyed men should prefer and feel more attracted towards women with blue eyes.
This calls for an experiment.
The eye color in the photographs of each model was manipulated so that a same face would be shown with either the natural eye color (e.g., blue) or with the other color (e.g., brown). Both blue-eyed and brown-eyed female participants showed no difference in their attractiveness ratings for male models of either eye color. Similarly, brown-eyed men showed no preference for either blue-eyed or brown-eyed female models. However, blue-eyed men rated as more attractive the blue-eyed women than the brown-eyed ones. We interpret the latter preference in terms of specific mate selective choice of blue-eyed men, reflecting strategies for reducing paternity uncertainty.
Acquired traits passed on to descendants:
“In our study, roundworms that developed resistance to a virus were able to pass along that immunity to their progeny for many consecutive generations,” reported lead author Oded Rechavi, PhD, associate research scientist in biochemistry and molecular biophysics at CUMC. “The immunity was transferred in the form of small viral-silencing agents called viRNAs, working independently of the organism’s genome.”
An interesting theoretical explanation:
According to the CUMC researchers, Lamarckian inheritance may provide adaptive advantages to an animal. “Sometimes, it is beneficial for an organism to not have a gene expressed,” explained Dr. Hobert. “The classic, Darwinian way this occurs is through a mutation, so that the gene is silenced either in every cell or in specific cell types in subsequent generations. While this is obviously happening a lot, one can envision scenarios in which it may be more advantageous for an organism to hold onto that gene and pass on the ability to silence the gene only when challenged with a specific threat. Our study demonstrates that this can be done in a completely new way: through the transmission of extrachromosomal information. The beauty of this approach is that it’s reversible.”
Beanie bow: Courtney Conklin Knapp
Suppose our minds have a hot state and a cool state. In the cool state we are rational and make calculated tradeoffs between immediate rewards and payoffs that require investment of time and effort. But when the hot state takes over we abandon deliberation and just react on instinct.
The hot state is there because there are circumstances where the stakes are too high and our calculations too slow or imperfect. You are being attacked, the food in front of you smells funky, that bridge looks unstable. No matter how confident your cool head might be, the hot state grabs the wheel and forces you to do the safe thing.
Suppose all of that is true. What does that mean when a situation looks borderline and you see that instincts haven’t taken over? Your cool, calculating head rationally infers that this must be a safer situation than it would otherwise appear. And you are therefore inclined to take more risks.
But then the hot state better step in on those borderline situations to stop you from taking those excessive risks. Except that now the borderline has moved a little bit toward the safe end. Now when the hot state doesn’t take over it means its even more safe, etc.
And of course there is the mirror image of this problem where the hot state takes over to make sure you take an urgent risk. A potential mate is in front of you but the encounter has questionable implications for the future. Physical attraction receives a multiplier. If it is not overwhelming then all of the warning signs are magnified.
“Corporations are evil” and we know this because they are always doing malicious things that are only later exposed. This often involves exploiting the complexity of transactions and the inability or unwillingness of consumers to wade through the thicket by surreptitiously ripping people off. For example, unauthorized charges inserted into phone bills, in a practice known as “cramming”, cost Americans $2 billion dollars a year, according to this article.
When something like this is discovered, the automatic reaction is to assume that the malice was intentional. They were sticking those charges in there to squeeze money out of consumers. And its basic economics that if they can secretly insert charges and make money they will. On the other hand, such a theory would appear to require you to accept they hypothesis that “corporations are evil” or at least they are cold-hearted profit maximizers.
But you can believe that corporations are not intentionally malicious and still assume that whenever there is a cold-hearted way to steal money they will do it. Because many malicious practices are not actively designed, rather they creep in and they are passively allowed to persist.
For example, those charges could have been legitimate under an outdated policy and when the policy was changed they forgot to remove them. Or some bumbling technician could have accidentally inserted them. Modern transactions are so complicated that random “mutations” are going to appear without any malicious intent and indeed without anyone noticing. This is a far more likely explanation than someone purposefully sticking them in there, especially if you doubt that “corporations are evil.”
Indeed, to have a conscious policy of ripping off unsuspecting customers requires instructing somebody to do that, and leaving a paper trail. Even a truly evil corporation understands that this is the wrong way to do it. The right way to do it is to structure the organization in a way that facilitates malice creep.
You don’t have to instruct anybody to allow mutant ripoffs to appear. They appear on their own, no paper trail required. All you need to do is to give weak incentives to the officers you have charged with making sure that you are not ripping anybody off. Nobody in your organization will have any knowledge of all the ways you are cheating your clients, not even you. By design.
There is an art to the design of an organization that cultivates malice creep. Because at the same time you have to stop “virtue creep” in its tracks. You don’t want unintended credits to randomly get inserted into the phone bill. What you need is a one-sided monitoring program. You wait around for lots of mutations to appear, you know that some are virtuous and some are malicious. Now getting rid of the virtuous ones and keep the malicious ones is easily done, just announce that its time to do some “cost-cutting.” Form an ad hoc task force to go through and find ways to restructure billing in ways that save the company money. They’ll just look at the credits and ignore the charges.
In terms of the long-run bottom line, Darwinism and Lamarckism are almost indistinguishable, but Occam’s razor favors Darwin. I would argue by the same principles that most of the malicious practices of organizations emerge by cultivated accident rather than by design.
Here’s what you already know: it’s a parasite that reproduces in the digestive system of cats. The eggs are excreted out and the vehicle is consumed by other animals in whose brains the eggs develop. Only when those brains are consumed by other cats does the cycle continue. In order to facilitate this process, chemicals are secreted inside the hosts’ brain to make them do things to increase the chance they will be eaten by cats. For example, rats with toxoplasma in their brains are not afraid of cats.
Here’s what’s new: toxoplasma is transferred from host to host through sexual contact in order to get closer to cats.
These are Toxoplasma cysts moving from rat to rat, so this exchange is kind of like a side track on the parasite’s life cycle. But it still benefits Toxoplasma, because it means it can infect even more potential prey that may get eaten by cats. And so the logic applies once more: if Toxoplasma can raise the odds of getting from infected males to uninfected females, it may have more reproductive success.
You know where this is going–it’s turning into a David Cronenberg horror movie with an all-rodent cast. Vyas wondered if there’s any difference in how female rats mate with infected and uninfected males. So he and his colleagues put a male rat with Toxoplasma at one end of a two-armed maze, and an uninfected male in the other arm. Females then got to choose which rat to approach. Vyans found that they preferred the infected males, spending more time with them and mating more often.
It’s pretty old, but worth reading given his new book.
Trivers has been teaching himself things and then growing bored with them his whole life. In 1956, when he was 13 and living in Berlin (his father was posted there by the State Department), he taught himself all of calculus in about three months. Around the same time, and with more modest success, Trivers-a skinny child picked on by bullies-tried to learn how to box, doing push-ups and covertly reading Joe Louis’s ”How to Box” in the school library.
Akubra Cadabra: Tobias Schmidt.
If you think about pain as an incentive mechanism to stop you from hurting yourself there are some properties that would follow from that.
When I was pierced by a stingray, the pain was outrageous. The puncture went deep into my foot and that of course hurts but the real pain came from the venom-laden sheath that is left behind when the barb is removed. Funny thing about the venom is that it is protein based and it can be neutralized by denaturing the protein, essentially changing its structure by “cooking” it as you would a raw egg.
How do you cook the venom when it is inside your foot? You don’t pee on it unless you are making a joke on a sitcom (and that’s a jellyfish anyway.) What you do is plunge your foot is scalding hot water raising the internal temperature enough to denature the venom inside. Here’s what happens when you do that. Immediately you feel dramatic relief from the pain. But not long after that you begin to notice that your foot is submerged in scalding hot water and that is bloody painful.
So you take it out. Then you feel the nerve-numbing pain from the venom return to the fore. Back in. Relief, burning hot water, back out. Etc. Over and over again until you have cooked all the venom and you are done. In all about 4 hours of soaking.
A good incentive scheme is reference-dependent. There’s no absolute zero. Zero is whatever baseline you are currently at and rewards/penalties incentivize improvement relative to the baseline. When the venom was the most dangerous thing, the scalding hot water was painless. Once the danger from the venom was reduced, the hot water became the focus of pain. And back and forth.
Second Observation. After three weeks of surfing (minus a couple of days robbed by my stingray friend) I came away with a sore shoulder. Rotator cuff injuries are common among surfers, especially over the hill surfers who don’t exercise enough the other 11 months of the year. The interesting thing about a rotator cuff injury is that the pain is felt in the upper shoulder, not at the site of the injury which is more in the area of the shoulder blade. It’s referred pain.
In a moral hazard framework the principal decides which signals to use to trigger rewards and penalties. Direct signals of success or failure are not necessarily the optimal ones to use because success and failure can happen by accident too. The optimal signal is the one that is most informative that the agent took the appropriate effort. Referred pain must be based on a similar principle. Rotator cuff injuries occur because of poor alignment in the shoulder resulting in an inefficient mix of muscles doing the work. Even though its the rotator cuff that is injured, the use of the upper shoulder is a strong signal that you are going to worsen the injury. It may be optimal to penalize that directly rather than associate the pain with the underlying injury.
(Drawing: Scale Up Machine Fail, from www.f1me.net.)
If you are programming a robot to vacuum your floors here’s one thing you would never consider doing: endow the robot with feelings of happiness and sadness and teach it to be happy when the floor is clean and unhappy when it is dirty.
But evolution led us to a state of affairs where emotions are what motivate us to do our jobs. How could such a kludge arrive.
Here is a story. Primitive organisms are reproduction machines. They need a certain chemical in the environment, and when they can obtain that fuel they can reproduce.
So the most successful primitive organisms are those that are the best at finding fuel. Natural selection favors those that seek fuel.
Next the organisms get more complicated. They have to make decisions that involve more than just immediate reproduction. They have intertemporal tradeoffs, multi-dimensional consumption, etc.
There is infrastructure in place to simplify this transition. The organisms that have survived to this stage are the organisms that seek fuel. They have built and learned systems for doing what is necessary to get fuel. So fuel is a simple and effective incentive mechanism.
The organism could evolve a mechanism for storing and later releasing fuel. Fuel is released when the organism takes certain actions. Fuel-seeking organisms will take those actions. Natural selection will favor the organisms that release fuel for the right actions.
Now remember that fuel is the energy needed for the most primitive functions of the organism. When this fuel is released the organism gets a boost of that energy.
A boost of energy is a big part of what we call happiness.
(subject to the usual disclaimer, this is based on some conversations with Balasz Szentes.)
Normally we understand the (near) 50-50 male/female population sex ratio with this simple model: if there were more males than females then individuals who are genetically disposed to have female children will have more grandchildren because their female children will find more mates. Thus females will increase in proportion, restoring the balance.
But here’s the interesting thing. That model doesn’t work for humans (and many other species) and in fact 50-50 is highly unstable, with potentially catastrophic consequences.
Suppose that a male has a mutation on his Y chromosome which causes him to produce Y-chormosome sperm that swim faster than his X-chromosome sperm. Then he will have only boys. And his boys will have the same gene and the same super Y-chromosome sperm.
Now suppose that his male children have an equal chance of mating as all other males in the population. Then our original mutant will have more male grandchildren than other males of his generation. Thus, the proportion of this super-Y gene increases in the population, and this trend continues generation after generation.
The balance is not being restored anymore. In fact eventually the super-Y’s dominate the male population. And that means that all offspring in all matings are boys. That means very little reproduction can happen because there are so few females. And the species goes exctinct.
I learned this from a paper by W. D. Hamilton called Extraordinary Sex Ratios.
It is a challenge for evolutionary theory to explain the prevalence of sexually reproducing species. That’s because of the twofold cost of sex: a sexually reproducing species produces half as many offspring per generation as an asexually reproducing population of the same size. So not only must there be some other advantage to sexual reproduction, it has to be large enough to outweigh that substantial cost.
One theory is that the genetic mixing that comes from sex allows a species to shed disadvantageous mutations. An asexual species can only accumulate them. This advantage can be large enough to overcome the twofold cost of sex. But the problem with this theoretical explanation is that in these models the advantage of sex is too large, so large that the kind of sex we see universally among all sexually reproducing species, sex between two parents, is dominated by tri-parental sex. This was shown by Perry, Reny, and Robson who consider a particular kind of menage a trois in which each mating requires two males and one female, and each offspring receives half of its genetic material from the mother and one quarter from each of the fathers.
This avoids a tri-fold cost of sex:
Because the cost of males is determined not by the ratio of males to females in each mating instance but, rather, by the population ratio of males to females, de-termining the population ratio is central. We therefore turn to Fisher’s celebrated equilibrium argument (Fisher, 1930). Applying the same logic to 1/2 – 1/4 – 1/4 sex, we note first that the total reproductive value of all of the males in any generation is precisely equal to that of all of the females in that generation. This is because, un-der 1/2-1/4-1/4 sex, all of the females supply half of the genes of all future generations. But then the remaining half must be supplied by all of the males. Consequently, as Fisher argued, equilibrium requires the offspring sex ratio to equate parental expenditure on male and female offspring. Maintaining the usual assumption that offspring of either sex are equally costly to raise to maturity, we conclude that the equilibrium sex ratio must be one–each male therefore mates with two females and vice versa. But this means that the cost of males is twofold–there is no additional cost of males over biparental sex.
I bring this up because (in an older working paper version) they also considered the leading competing theory for the advantage of sexual reproduction, The Red Queen hypothesis. Here the argument is that species are constantly trying to out-evolve parasites. Genetic mixing makes them a moving target. Perry, Reny, and Robson showed that, unlike the deleterious mutations theory, the Red Queen story rationalizes biparental sex over other forms of sex. Thus, from the point of view of sex as an evolved mechanism for solving some problem, only the Red Queen can explain the kind of sex we see.
And I bring that up because just last week I heard this story about a new experiment that validates the Red Queen hypothesis.
Tyler Cowen quotes Richard Dawkins:
Isn’t it plausible that a clever species such as our own might need less pain, precisely because we are capable of intelligently working out what is good for us, and what damaging events we should avoid? Isn’t it plausible that an unintelligent species might need a massive wallop of pain, to drive home a lesson that we can learn with less powerful inducement?
There is an alternative to pain as an incentive mechanism: dispensing with incentives altogether and just programming the organism with instructions to follow. And if the organism doesn’t already have “feelings” as a part of its infrastructure then the instructions are the only alternative. The big question for theories of pain and pleasure as an incentive mechanism is why mother nature as Principal bothers with incentives at all.
I spent the weekend in bed with the flu. Sunday morning, on the tail end of it, I popped a few Advil to bring the fever down so I could semi-enjoy Father’s Day. Was I making a mistake?
As I understand it, my body elevates its temperature as a defense mechanism. Evolution has been operating long enough to have a pretty well-calibrated trade-off between the losses of reduced activity from the fever versus the speed and probability of a successful recovery. Is my intervention distorting away from the optimum?
- Arguably I have private information about idiosyncratic conditions and Nature is calibrated only to the average state. Note that while this hypothesis justifies my use of Advil on Father’s Day, it also implies that I should go short on Advil on other days.
- And anyway Nature has given me the infrastructure to condition physiology on my knowledge of immediate environmental conditions. For example when I know that I am in danger, the body re-allocates resources to help me escape. What makes this any different?
- My objective is probably different. In Mother Nature’s eyes I am just a vessel from which offspring should spring forth. She could care less whether I get to practice Pink Floyd’s San Tropez on the piano with my daughters. So Nature’s revealed preference for activity is necessarily weaker than mine.
- But wait, my personal preference for non-reproductive activity is also something that Nature shaped. So what would explain the wedge?
- If I am making the wrong decision by taking Advil it’s not because I have the wrong preferences but because Advil is something Nature never expected. She has me well-trained when it comes to the fundamentals but she hasn’t had time to design my direct preference for the intermediate good Advil. She must leave it up to me to do the calculation of its implied tradeoffs in terms of the fundamentals. It’s only because of my miscalculation that I am making a mistake.
Clearly the reason that sex is so pleasurable is because that motivates us to have a lot of it. It is evolutionarily advantageous to desire the things that make us more fit. Sex feels good, we seek that feeling, we have a lot of sex, we reproduce more.
But that is not the only way to get motivated. It is also advantageous to derive pleasure directly from having children. We see children, we sense the joy we would derive from our own children and we are motivated to do what’s necessary to produce them, even if we had no particular desire for the intermediate act of sex.
And certainly both sources of motivation operate on us, but in different proportions. So it is interesting to ask what determines the optimal mix of these incentives. One alternative is to reward an intermediate act which has no direct effect on fitness but can, subject to idiosyncratic conditions together with randomness, produce a successful outcome which directly increases fitness. Sex is such an act. The other alternative is to confer rewards upon a successful outcome (or penalties for a failure.) That would mean programming us with a desire and love for children.
The tradeoff can be understood using standard intuitions from incentive theory. The rewards are designed to motivate us to take the right action at the right time. The drawback of rewarding only the final outcome is that it may be too noisy a signal of whether he acted. For example, not every encounter results in offspring. If so, then a more efficient use of rewards to motivate an act of sex is to make sex directly pleasurable. But the drawback of rewarding sex directly is that whether it is desirable to have sex right now depends on how likely it is to produce valuable offspring. If we are made to care only about the (value of) offspring we are more likely to make the right decision under the right circumstances.
Now these balance out differently for males than for females. Because when the female becomes pregnant and gives birth that is a very strong signal that she had sex at an opportune time but conveys noisier information about him.That is because, of course, this child could belong to any one of her (potentially numerous) mates. Instilling a love for children is therefore a relatively more effective incentive instrument for her than for him.
As for love of sex, note that the evolutionary value of offspring is different for males than for females because females have a significant opportunity cost given that they get pregnant with one mate at a time. This means that the circumstances are nearly always right for males to have sex, but much more rarely so for females. It is therefore efficient for males to derive greater pleasure from sex.
(It is a testament to my steadfastness as a theorist that I stand firmly by the logic of this argument despite the fact that, at least in my personal experience, females derive immense pleasure from sex.)
Drawing: Misread Trajectory from www.f1me.net
She wrote this convincing essay on happiness and parenting. Parents seem to be less happy but we shouldn’t read too much into that. She brings together all kinds of economic theory and data and along the way she cites a paper I like very much by Luis Rayo and Gary Becker:
Nobel Prize–winning economist Gary Becker, writing with Luis Rayo, has argued this contrary position. In their view, while “happiness and life satisfaction may be related to utility, they are no more measures of utility than are other dimensions of well-being, such as health or consumption of material goods.”[5] Or having kids. Children may make you less happy, but still raise your utility. Devout neoclassical reasoning leads Becker and Rayo to infer from the fact that we are having kids that they raise your utility (or at least they raise the utility of those who make this choice).
Rayo and Becker argued that happiness should be thought of as the carrot that gets us to make good decisions. But happiness is a scarce resource. There’s a limit to how happy you can be. So it has to be used in the most economical way. In their theory the most economical way to use happiness is to give an immediate, and completely transitory boost of happiness to reward good outcomes. You have sex, you get rewarded. It results in conception, that’s another reward. But then you are back to the baseline so as to maximize the range available for further rewards (and penalties) motivating behavior going forward. Bygones are bygones.
With that theory it makes no sense to look at a cross section of the population, compare how happy are people who did X relative to people who didn’t do X, and conclude on the basis of that whether its good to do X.
And by the way, if there is anything we can expect evolutionary incentives to have a good handle on, its whether or not to have kids. That’s the whole ballgame. If happiness is there to motivate us to succeed evolutionarily then you better have a good argument why Nature got it wrong. One place to look might be on the quantity/quality tradeoff. Perhaps the relative price of quality versus quantity has declined in modern times and Nature’s mechanism is tuned to an obsolete tradeoff. If so, then people feel a motivation to have more kids than they should. The prescription then would be to resist the temptation you feel to have another kid and instead invest more in the ones you have. Unless you want to be happy.
Apparently it’s biology and economics week for me because after Andrew Caplin finishes his fantastic series of lectures here at NU tomorrow, I am off to LA for this conference at USC on Biology, Neuroscience, and Economic Modeling.
Today Andrew was talking about the empirical foundations of dopamine as a reward system. Along the way he reminded us of an important finding about how dopamine actually works in the brain. It’s not what you would have guessed. If you take a monkey and do a Pavlovian experiment where you ring a bell and then later give him some goodies, the dopamine neurons fire not when the actual payoff comes, but instead when the bell rings. Interestingly, when you ring the bell and then don’t come through with the goods there is a dip in dopamine activity that seems to be associated with the letdown.
The theory is that dopamine responds to changes in expectations about payoffs, and not directly to the realization of those payoffs. This raises a very interesting theoretical question: why would that be Nature’s most convenient way to incentivize us? Think of Nature as the principal, you are the agent. You have decision-making authority because you know what choices are available and Nature gives you dopamine bonuses to guide you to good decisions. Can you come up with the right set of constraints on this moral hazard problem under which the optimal contract uses immediate rewards for the expectation of a good outcome rather than rewards that come later when the outcome actually obtains?
Here’s my lame first try, based on discount factors. Depending on your idiosyncratic circumstances your survival probability fluctuates, and this changes how much you discount the expectation of future rewards. Evolution can’t react to these changes. But if Nature is going to use future rewards to motivate your behavior today she is going to have to calibrate the magnitude of those incentive payments to your discount factor. The fluctuations in your discount factor make this prone to error. Immediate payments are better because they don’t require Nature to make any guesses about discounting.
- There is an inverse relationship between how carefully you stack the dishes inside the dishwasher and how tidy you keep it outside in your kitchen.
- In addition to funny-haha and funny-strange there is a third category of joke where the impetus for laughter is that the comedian has made some embarrassing fact that is privately true for all of us into common knowledge.
- It would be too much of an accident for 50-50 genetic mixing to be evolutionarily optimal. So to compensate we must have a programmed taste either for mates who are similar to us or who are different.
- It is well known that in a moderately sized group of total strangers the probability is about 50% that two of them will have the same birthday. But when that group happens to be at a restaurant the probability is virtually 1.
Following up on the Trivers-Willard hypothesis. The evidence is apparently that promiscuity, a trait that confers more reproductive advantage on males than females, is predictive of a greater than 50% probability of male offspring. A commenter claimed that there is a bias in favor of male offspring when the mother is impregnated close to ovulation and wondered whether the study controlled for that. A second commenter pointed out that there is no reason to control for that because that may be exactly the channel through which the Trivers-Willard effect works.
So now put yourself in the shoes of the intelligent designer. Suppose you are given that promiscuity is such a trait. You are given control over the male-female proportion of offspring and you are designing the female of the species. What you want to do is program her to have male offspring when she mates with a promiscuous male. But you cannot micromanage because there is no way to condition this directly on the promiscuity of the mate. The best you can do is vary the sex proportions conditional on biological signals, for example the date in the cycle.
How would you do this? Of all the “states of the system” that you can condition on, you would find the one such that conditional on having sex in that state, the relative likelihood that her partner was the promiscuous type was maximized. You would program her to increase the proportion of male offspring in those states.
Is sex close to ovulation such a signal? I don’t see why. But we could think of some that would qualify. How about the signal that he is delivering a small quantity of sperm? The encounter lasted longer than usual, this is the first time she had sex in a while, these sperm have not been seen before, etc…
According to the Trivers-Willard Hypothesis, individuals possessing a trait which improves the reproductive success of males more than females will be more likely to give birth to male offspring than to female offspring. I came across a study that claims to support the hypothesis where the trait in question is promiscuity.
Our analyses of two large nationally representative samples, from the General Social Survey in 1994 and the National Longitudinal Study of Adolescent Health, confirm this prediction. Controlling for a large number of social demographic factors that might be expected independently to influence offspring sex ratios, unrestricted sociosexual orientation significantly increases the odds that the first child is a boy. One standard deviation increase in the unrestrictedness of sociosexual orientation increases the odds of having a son by 12-19%.
That seems like a large effect, if true. Chullo chuck: Barking Up The Wrong Tree.
When your doctor points to the chart and asks you to rate your pain from 0 to 5, does your answer mean anything? In a way, yes: the more pain you are in the higher number you will report. So if last week you were 2 and this week you are 3 then she knows you are in more pain this week than last.
But she also wants to know your absolute level of pain and for that purpose the usefulness of the numerical scale is far less clear. Its unlikely that your 3 is equal in terms of painfulness to the next guy’s 3. And words wouldn’t seem to do much better. Language is just too high-level and abstract to communicate the intensity of experience.
But communication is possible. If you have driven a nail through your finger and you want to convey to someone how much pain you are in that is quite simple. All you need is a hammer and a second nail. The “speaker” can recreate the precise sensation within the listener.
Actual mutilation can be avoided if the listener has a memory of such an experience and somehow the speaker can tap into that memory. But not like this: “You remember how painful that was?” ”Oh yes, that was a 4.” Instead, like this: “You remember what that felt like?” “OUCH!”
Memories of pain are more than descriptions of events. Recalling them relives the experience. And when someone who cares about you needs to know how much help you need, actually feeling how you feel is more informative than hearing a description of how you feel.
So words are at best unnecessary for that kind of communication, at worst they get in the way. All we need is some signal and some understanding of how that signal should map to a physical reaction in the “listener.” If sending that signal is a hard-wired response it’s less manipulable than speech.
Which is not to say that manipulation of empathy is altogether undesirable. Most of what entertains us exists precisely because our empathy-receptors are so easily manipulated.
You manage a colony of slave-maker ants. It’s a small colony (not a knock on you, all slave-maker ant colonies are small) so you have only a handful of scouts to send out on an enslavement mission. Do you target a similarly weak colony (better odds) or the biggest and strongest around (better slaves)? According to this account of a study published in Animal Behavior, you risk it and go for the big prize.
It’s fun to theorize why:
Now, like most animal fables, this one can be spun in any number of ways. (Ants are particularly suitable for, or susceptible to, this.) Are the populous, well-defended colonies doing anything wrong? Do these attacks work because whoever’s running the big, powerful colony doesn’t mind losing a few small members? Is the answer more defenses, or subtler ones? Do you change how you live because of a small band of violent actors? Should the hostages fight back when they’re older? (They sometimes do.)
Homburg Howdyado: The Browser.
For while O’Donnell crusaded against masturbation in the mid-1990s, denouncing it as “toying” with the organs of procreation and generally undermining baby making, the facts are to the contrary. Evidence from elephants to rodents to humans shows that masturbating is—counterintuitively—an excellent way to make healthy babies, and lots of them. No one who believes in the “family” part of family values can let her claims stand.
You will find that opening paragraph in an entertaining article in Newsweek (lid lob: linkfilter.) It surveys a variety of stories suggesting that masturbation serves an adaptive role and was selected for by evolution. The stories given (hygiene, signaling (??)) are mostly of the just-so variety, but this is a case where we don’t need to infer exactly the reason. We can prove the evolutionary advantage of masturbation by a simple appeal to revealed preference.
There are lots of ways we can touch ourselves and among these, Mother Nature has revealed a very clear preference. You cannot tickle yourself. Because the brain has a system for distinguishing between stimuli caused by others and stimuli caused by ourselves. Nature puts this system to good use: such a huge fraction of sensory information comes from incidental contact with yourself that it has to be filtered out so that we can detect contact with others.
Mother Nature could have used this same system to put an end to masturbation once and for all: simply detect when its us and mute the sensation. No gain, no Spain. Instead, she made an exception in this case. She must have had a good reason.
Poker players know that the eyes never lie. Indeed your eyes almost always signal your intentions for the simple reason that you have to see what you intend to do.
This is an essential difference between communication with eye movement/eye contact and other forms of communication. The connection between what you know and what you say is entirely your choice and of course you will always use this freedom to your advantage. But what you are looking at and where your eyes move are inevitably linked.
Naturally your friends and enemies have learned, indeed evolved to exploit this connection. Even the tiniest changes in your gaze are detectable. As an example, think of the strange feeling of having a conversation with someone who has a lazy eye.
Given that Mother Nature reveals such a strong evolutionary advantage for reading another’s gaze the question then arises why we have not evolved to mask it from those who would take advantage? The answer must be that it would in fact not be to our advantage.
With any form of communication, sometimes you want to be truthful and other times you want to deceive. The physical link between your attention and your gaze means that, for this particular form of communication you can’t have it both ways. Outright deception being impossible, at best Nature could hide our gaze altogether, say by uniformly coloring the entire eye.
But she chose not to. By Nature’s revealed preference, this particular form of honesty is evolutionarily advantageous, at least on average.
Here is the abstract from a paper by Matthew Pearson and Burkhard Schipper:
In an experiment using two-bidder first-price sealed bid auctions with symmetric independent private values, we collected information on the female participants’ menstrual cycles. We find that women bid significantly higher than men in their menstrual and premenstrual phase but do not bid significantly different in other phases of the menstrual cycle. We suggest an evolutionary hypothesis according to which women are genetically predisposed by hormones to generally behave more riskily during their fertile phase of their menstrual cycle in order to increase the probability of conception, quality of offspring, and genetic variety.
Believe it or not, this contributes to a growing literature.
I went through a long showdown with tendonitis of the hamstring. At its worst it was a constant source of discomfort that occupied at least a fraction of my attention at all times. I knew that I had to heal before I would get back my to usual smiling happy self. So I worked hard, stretching, walking, running: rehabilitating.
My hamstring doesn’t bother me much anymore. But you know what? Now that it no longer dominates the focus of my attention, I am reminded that my back hurts, as it always has. But I had completely forgotten about that for the last year or so because during that time it didn’t hurt.
So I am not the content, distraction-free person I expected to be. Now that I have solved the hamstring problem my current distractions draw my attention to the next health-related job: keep my back strong, flexible, and pain-free.
This is a version of the focusing illusion. People are motivated by expected psychological rewards that never come. The classic story is moving to California. People in Michigan declare that they would be much happier if they lived in California, but as it turns out people in California just about as miserable as people who still live in Michigan.
Pain and pleasure make up the compensation package in Nature’s incentive scheme. Our attention is focused on what needs to be done using the lure of pleasure and the avoidance of pain. And if it feels like she is repeatedly moving the goal posts, that may be all part of the plan according to a new paper by Arthur Robson and Larry Samuelson.
They model the way evolution shapes our preferences based on two constraints: a) there’s a limit to how happy or unhappy we can be and b) emotional states are noisy. Emotions will evolve into an optimal mechanism for guiding us to the best decisions. Following the pioneering research of Luis Rayo and Gary Becker, they show that the most effective way to motivate us within these constraints is to use extreme rewards and penalties. If we meet the target, even by just a little, we are maximally happy. If we fall short, we are miserable.
This is the seed of a focussing illusion. Because after I heal my hamstring Nature again needs the full range of emotions to motivate me to take care of my back. So after the briefest period of relief, she quickly resets me back to zero, threatening once again misery if I don’t attend to the next item on the list. If I move to California, I enjoy a fleeting glimpse of my sought-after paradise before she re-calibrates my utility function, so that now I have to learn to surf before she’ll give me another taste.
This is a very interesting article that has the unfortunate title “Plants Can Think And Remember.” (Unfortunate because the many links to it that I have seen come with snarky comments like “Whatcha gonna do now vegetarians??”)
It reminds me of a great joke: Three scientists are on the committee to decide mankind’s greatest invention. The engineer is arguing for the internal combustion engine, the doctor is arguing for the X-ray machine and Martha Stewart is arguing for the Thermos. ”The Thermos, you’ve got to be kidding?” Sez Martha “Well you see it keeps hot things hot and cold things cold.” They look perplexed. ”Yeah, big deal.” Martha: ”How does it know??”
The article is about some pretty sophisticated ways that plants respond to signals in their environment. That is very cool. Kudos to the Plant Kingdom. But while, there may be something in the underlying research that justifies saying that plants “think”, I rather doubt it, and it is definitely not to be found in this journalistic account. Look:
In their experiment, the scientists showed that light shone on to one leaf caused the whole plant to respond.
“We shone the light only on the bottom of the plant and we observed changes in the upper part,” explained Professor Stanislaw Karpinski from the Warsaw University of Life Sciences in Poland, who led this research.
When I light a match to the coals at the bottom of my charcoal chimney, eventually all of them ignite and turn red even the ones on the top. My charcoal can think.
Then there’s stuff about “memory.” But I already knew that plants had memory. When I give my grass water today, it is green next week. When I don’t give my grass water today, it is brown next week. The grass changes its color next week depending on whether I give it water today. It remembers.
Here is a good metaphor for a problem Mother Nature has to solve. A small child is playing on the equipment at the playground. The child knows what she is physically capable of but doesn’t know what is safe. If Nature knew about swings and see-saws and monkey bars she would just encode their riskiness into the genes of the child and let the child do the optimization.
But these things came along much too recently for Nature to know about them. Fortunately Nature knows that whatever is in the child’s world was pretty likely also in the parents’ world and by now the parents have learned what is safe. So Nature can employ the parent as her agent.
But in this family-firm, the child is a specialist too. For one thing she has up-to-the-minute information about her physical abilities which change too quickly for the parents to keep track of. But just as importantly the child is the cheapest source of information about what’s in front of her. Nature could press the parent into service again to investigate the set of possible activities available to the child, but this would be costly to the parent (for whom this carrier of only half of his genes is just one of many priorities) and so would require extra incentives and anyway that information is more directly accessible to the child.
So Nature’s organizational structure utilizes a tidy division of labor. The child’s job is to identify the feasible set and the parent’s job is to veto all the alternatives that are too dangerous. One last constraint explains the reckless kid. The child cannot communicate the feasible set to the parent. This leads to the third-best solution. The child just picks something nearby, say the rope bridge, and starts climbing on it. The parent is stationed nearby ready to intervene whenever the child’s first choice is too dangerous.
And thus the seeds of much later conflict are sown.
Like me, ants like dark houses/nests with small entrances. Facing a choice between a dark nest with a large entrance (option A) and a light nest with a small entrance (option B), an ant colony faces a trade-off. Some go this way to A and some go that way to B. Suppose we add a third decoy nest option D. Option D is as dark as A but has an even larger entrance. It is thus dominated by A but not by B. How will the ant colony’s behavior change when they face the three options together versus just A and B?
Rational choice theory says that the fractions choosing A and B should not change. Option D is dominated and should never chosen and hence is an irrelevant alternative. Its presence or absence should not affect the choice between A and B.
One psychological theory suggests that the proportion choosing A should go up. Option D helps to crystallize the advantages of option A (the smaller entrance). This may increase the perception of the advantages of A over B as well leading to a change in the proportion of ants choosing A over B.
So what actually happens?
A controlled experiment by Edwards and Pratt answers this question. Edwards and Pratt built nests with the properties above and made ant colonies make repeated binary and ternary choices. They randomized the order of choices, where the nests were located etc. And because they were experimenting with ants, they could cruelly force the choice of nest upon the ants by destroying the old nest the ants lived in by removing it’s roof.
They find no significant change in the proportions choosing A vs B when the decoy D is present. Ant colonies are rational and do not violate the axiom of independence of irrelevant alternatives (IIA).
In other work, Pratt shows that ant colonies obey transitivity (i.e. if a colony prefers A to B and B to C, it prefers A to C).
Why are ant colonies more rational than individual humans? The authors offer a cool hypothesis: choice between colonies is typically made by sending independent scouts sent to the different options. No scout visits different locations. The scouts reports are simply compared and the best option is chosen. A human being contemplates all the choices by herself and has a harder time comparing the attributes independently leading to a violation of IIA.
An ant colony is like a well performing and coordinated decentralized firm with employees passing information up the hierarchy and efficient decisions coming down from the center Can we import lessons into designing firms? Alas, I believe not. A human scout evaluating a decision/option will not be as impartial an ant scout. He will exagerrate its qualities, hoping his option “wins”. He hopes to get the credit for finding the implemented option, get promoted, receive stock options and retire young to the Bay Area. In other words, career concerns ruin a simple transfer of ant colony principles to firms. If we eliminate career concerns within the firm, we will induce moral hazard as there is no incentive to exert costly effort to find the best decisions for the firm. Ants in the same colony do not face the same issue as they are genetically related and have “common values”.
Still, a thought-provoking paper and it has many references to other papers that it builds on. I am going to read more of them.
(Hat tip to Christophe Chamley for the reference)
Via Barker, a pointer to a theory from evolutionary psychology that tears are a true signal that the person crying is vulnerable and in need.
Emotional tears are more likely, however, to function as handicaps. By blurring vision, they handicap aggressive or defensive actions, and may function as reliable signals of appeasement, need or attachment.
Usually you should be skeptical that signaling is evolutionarily stable. For example if tears convince another that you are defenseless then there is an evolutionary incentive to manipulate the signal. Convince someone you are defenseless and then take advantage of them.
A typical exception is when the signal is primarily directed toward a family member. Family members have common interests because they share genes. Less incentive to manipulate the signal means that the signal has a better chance of being stable. And babies of course have few other ways of communicating needs.
Of course children eventually do start manipulating the signal. They learn before their parents do that they are becoming self-sufficient but they still have an incentive to free-ride on the parents’ care. Fake tears appear. But this is a temporary phase until the parents figure it out. Not surprisingly, once the child reaches adulthood, crying mostly stops: Nature takes away a still-costly but now-useless signal.
