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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.

It’s as if someone at the New York Times scanned this blog, profiled me, and assembled an article that hits every one of my little fleemies:

(Follow closely now; this is about the science of English.) Phoebe and Rachel plot to play a joke on Monica and Chandler after they learn the two are secretly dating. The couple discover the prank and try to turn the tables, but Phoebe realizes this turnabout and once again tries to outwit them.

As Phoebe tells Rachel, “They don’t know that we know they know we know.”

Literature leverages our theory of mind.

Humans can comfortably keep track of three different mental states at a time, Ms. Zunshine said. For example, the proposition “Peter said that Paul believed that Mary liked chocolate” is not too hard to follow. Add a fourth level, though, and it’s suddenly more difficult. And experiments have shown that at the fifth level understanding drops off by 60 percent, Ms. Zunshine said. Modernist authors like Virginia Woolf are especially challenging because she asks readers to keep up with six different mental states, or what the scholars call levels of intentionality.

And they even drag evolution into it.

To Mr. Flesch fictional accounts help explain how altruism evolved despite our selfish genes. Fictional heroes are what he calls “altruistic punishers,” people who right wrongs even if they personally have nothing to gain. “To give us an incentive to monitor and ensure cooperation, nature endows us with a pleasing sense of outrage” at cheaters, and delight when they are punished, Mr. Flesch argues. We enjoy fiction because it is teeming with altruistic punishers: Odysseus, Don Quixote, Hamlet, Hercule Poirot.

Cordobés address:  Marcin Peski.

Frances Xu wrote to me:

Someone asked me why evolution lets a bee die after it stings.  I don’t seem to have a good theory. I have a bad one: it shows that bees are of a crazy type, so people are more afraid of them. Just wonder if you have any thoughts on this.

There are two ways to phrase the question.  First, why would a bee sacrifice its life to sting me.  Second, why would Nature design the bee so that it dies after it stings?   The answer to the second question is that after stinging the bee’s life is not worth living.  The answer to the first is that it wasn’t worth much before either.

The queen honeybee uses sperm stored from her maiden flight to fertilize and lay eggs.  Time seems to be the only binding constraint on how many bees she can bring to life.  There is no opportunity cost because her capacity is essentially unlimited.   This means that the marginal bee has close to zero net marginal value for the colony.

The marginal bee’s value at birth incorporates the value of stinging together with the value of all of the other services it contributes to the colony.  When the bee loses its stinger it loses its ability to sting and its value to the colony drops a discrete amount.  Now its value to the colony is negative.  The cost in terms of demand on colony resources for survival outweighs the benefits.

At this point it is optimal for the colony that the bee should die.

Now if the bee were genetically identical to the colony then its interests would align perfectly and it would therefore also be in the bee’s interest to die.  In fact the bee is genetically identical only to a component of the colony:  those other bees produced from the sperm of the same drone.  (Roughly 15 drones mate with the queen.)  Since the bee’s contribution to the colony is presumably shared by all bees, this means in fact that the bee has even less incentive to go on living.

The final variable is whether the bee could expect someday to mate with a new queen and get his genes into a new colony.  That prospect would give the bee reason to live.  But worker bees are sterile.

Drones are not.  And drones don’t die when they sting.  (update: drones don’t have stingers.)

There are many differences between men and women that create delicate asymmetries in a relationship.   But few are as polarizing and mysterious as a man’s appreciation of his own farts.

Beneath the Dutch ovens, pulled fingers, and silent but deadlies, there must be a scientific explanation and I believe that, as usual, it all boils down to evolution and sex.

Monogamy is relatively rare among animals and for good reason.  Monogamous males forego the opportunity to have offspring by other mates.  This sacrifice in quanitity is evolutionarily beneficial for the male only if monogamy has some offsetting benefits.  The obvious benefit would be the male’s investment the survival probability of the offspring in the monogamous relationship.  But the return on this investment is always threatened by the female’s incentive for cuckoldry:  secretly being impregnated by a superior male and passing on the burden of rearing to the cuckold.

The only way this incentive can be mitigated is the presence of a signature that identifies the child as the true descendant of the monogamous father.  There are in principle many ways this signature could have evolved, but natural selection favors solutions that piggyback on existing physiology and minimize incidental costs.  The passing of gas makes an ideal signature because of two facts.  First, the rapid development of intestinal flora means that infants are already especially gassy.  Second, as documented by Professor Hugh Kuddachize of the University of Wafting, the susceptibility to various lactose-feeding bacteria is determined by genes on the Y-chromosome.

That is, a male infant’s farts will smell similar to those of his biological father.  This enables the father to determine parenthood at an early stage.  And because the mother can’t know in advance whether the child will be male or female, this 50% detection probability is enough to dissuade her from sneaking around.  And the father’s pleasure at the smell of his son’s farts is Nature’s incentive mechanism to keep him at home while still shielding him from cuckoldry.

The humorous byproduct of this development of course is that men love the smell of their own farts.  And we can now understand the asymmetry.  There is no uncertainty about maternal parentage, so no need for any signature.  On the other hand, bacterial infection of the intestine is a signal of the child’s health and Nature accordingly programs the mother to respond to the olfactory expression with alarm.  The father’s farts carry the same signature and induce the same response.

Understanding our evolutionary origins helps us understand ourselves and in this case it teaches us to appreciate and indeed cherish the gas that keeps the family together.

Female digger wasps prey on katydids.  But they don’t kill them.  They paralyze them and then store them in little holes they dig in the ground.  They are preparing nests where they will lay eggs and when the eggs hatch, the larvae will feast on the katydids.

Richard Dawkins and John Brockman observed that it sometimes happens that two digger wasps are unknowingly tending the same nest.  Naturally, once they figure this out, there’s going to be a fight.  Dawkins and Brockman noticed two things about these fights.  First, the wasp that wins is usually the one that has contributed more katydids to the common nest.  Second, the duration of the fight is predicted by the number of katydids contributed by the eventual loser.

For Dawkins and Brockman the wasps are revealing a sunk-cost fallacy.  Evidently, their willingness to fight is not determined by the total reward, but instead by the individual wasp’s past investment.  The more they invested, the more they are willing to fight.

A more nuanced interpretation is that the wasps’ behavior is not a fallacy at all, but a clever hack.  The wasps really do care about the total value of the nest, but their best estimate of that value is (proportional to) their own contribution to it.  For example, a wasps may be able to “remember” the number of katydids she paralyzed (and she must if she is able to condition her fighting intensity on that number) but not be able to count the number of katydids in the nest.  The former is going to be correlated with the latter.

Sunk cost bias:  a handy trick.

People seem to care not just about their own material success but how it measures up to their peers. There is probably a good evolutionary reason for this. Larry Samuelson has shown one way to formalize this idea in this paper.

But here’s a different story and one that is extremely simple. Imagine a speed skating competition with 10 competitors. Suppose that 8 of them skate their heats solo with no knowledge of the others’ times. The remaining 2 also have no knowledge of the others’ times except that they race simultaneously side by side.

Other things equal, each of the two parallel skaters has a greater than 1/10 chance of winning.

You often hear that an incomplete course of antibiotics can promote the emergence of drug-resistant bacteria.  Patients are told not to stop taking antibiotics just because you feel better but instead to always complete the full dosage.  This is obviously partly for the health of the patient.  But it is also said to guard against drug-resistance.

I have never been able to understand the logic.  So I sat down to try to figure it out.  I came up with one possible answer but it seems second-order to me so I am not sure if its the primary reason.

One thing that seems obvious is that every time you  ingest antibiotics you create natural selection pressure within your body that favors any drug-resistant mutants that are there.  This is why the headline cause of super-bugs is overuse of antibiotics.  For example antibiotics are often prescribed and taken for non-bacterial illnesses like the common cold.  Also, antibiotics are given to livestock that people eventually eat.

But this doesn’t get us to the recommendation to complete your course of antibiotics.  Since the problem is the antibiotics, it tells us to use them as little as possible.  How could it be that the first dose helps the super-bugs, but the last dose hurts them?  They are drug-resistant after all, right?

I used to think that it must be that the selection pressure increases the rate of mutation.  This may be true but I don’t think it’s enough to support the complete-course policy.  Suppose I am halfway done with the recommended dosage and I stop.  My usage so far has encouraged mutations and I may be infected now with a drug-resistant strain.  Now the mutation-inducing effect is irrelevant because the superbugs are already there.  Their natural growth rate is going to dwarf any additional growth due to mutations.

More generally, since every prescription of antibiotics is a public health cost, then every time I continue to take my doses I am creating the same externality.

I finally hit on one idea which has to do with competition within the body among bugs of differing levels of resistance.  Start with this observation.  If I have a super-bug in me and I continue to take anti-biotics, I kill off all the wimpy-bugs leaving the super-bugs to have free reign over my body.  Presumably they grow faster without the competition.  OK.  But that seems again to suggest that, at least from a public health perspective, I should stop taking the drug so that the wimpy-bugs can outcompete the super-bugs.

So we add one twist to the model.  Suppose that my body has a baseline system of defenses that can fight off any bad guy, super- or otherwise, as long as there are sufficiently few of them.  Then, if I stop taking the drug too early, my defenses may still overwhelmed by the sheer numbers.  All the bugs start growing again and if I started with just a few super-bugs in me, then when I start to show symptoms again I now have lots of them.  However, had I continued to completion, all of the wimpy-bugs would be gone and my body’s natural defenses could have mopped up the few super-bugs that were left hanging around.

It’s a coherent theory.  But I am not sure I believe that it is quantitatively important.  So I still find the advice a little mysterious.  Any of you know better?

Ingenious new support for that view:

The mighty insect colonies of ants, termites and bees have been described as superorganisms. Through the concerted action of many bodies working towards a common goal, they can achieve great feats of architecture, agriculture and warfare that individual insects cannot.

That’s more than just an evocative metaphor. Chen Hou from Arizona State University has found that the same mathematical principles govern the lives of insect colonies and individual animals. You could predict how quickly an individual insect grows or burn food, how much effort it puts into reproduction and how long it lives by plugging its body weight into a simple formula.  That same formula works for insect colonies too, if you treat their members as a collective whole.

And this is not just an accounting trick.  If you take a “colony” of, say, 100 people and and measure how much energy their bodies use it would be 100 times the energy that a single body uses (duh.)  But a single animal that weighs 100 times as much as a human uses only 100^(3/4) ≈ 32 times as much energy as a single human.  There are economies of scale within a single organism but not across.

Except with ant colonies.  The mass to energy ratio of the colony as a whole follows the same law that governs indivduals of non-colony animals.  Via Not Exactly Rocket Science.

Tongue-in-cheek relationship advice from evolutionary psychology (via Mindhacks.)

Some Darwinists might say your optimal strategy would be to pair-bond with the older male but surreptitiously allow the younger, sexy male to fertilise you. But be careful, most men consider being cuckolded the greatest of betrayals.

And how about this?

You should have your husband medically assessed. It may be that some form of genetic disorder underlies his erratic behaviour, in which case he will need counselling and support. But you will also need to inform your daughters so that, if they are carriers, they do not themselves mate with men suffering from the same condition.

A simple implication of sexual selection is that there should be a correlation between features that attract us sexually and characteristics that make our offspring more fit. Here is an article that studies the link between physical attraction and success in sport.

The better an American football player, the more attractive he is, concludes a team led by Justin Park at the University of Bristol, UK. Park’s team had women rate the attractiveness of National Football League (NFL) quarterbacks: all were elite players, but the best were rated as more desirable.

Meanwhile, a survey of more than a thousand New Scientist Twitter followers reveals a similar trend for professional men’s tennis players.

Neither Park nor New Scientist argue that good looks promote good play. Rather, the same genetic variations could influence both traits.

“Athletic prowess may be a sexually selected trait that signals genetic quality,” Park says. So the same genetic factors that contribute to a handsome mug may also offer a slight competitive advantage to professional athletes.

Studies like this are prone to endogeneity problems because success also feeds back on physical attraction. At the extreme, we know who Roger Federer is and that gets in the way of judging his attractiveness directly. More subtly, if you show me pictures of two anonymous athletes, the one who is more successful has probably also trained better, eaten better, been raised differently and these are all endogenous characteristics that affect attractiveness directly. Knowing that they correlate with success doesn’t tell us whether “success genes” have physically attractive manifestations.

One way to improve the study would be to look at adopted children. Show subjects pictures of the athletes’ biological parents and ask the subjects to rate the attractiveness of the parents. Then correlate the responses with the performance of the children. If these children were raised by randomly selected parents (obviously that is not exactly the case) then we would be picking up the effect of exogenous sources of physical attractiveness passed on only through the genes of the parents.

And why stop with success in sport. Physical attractiveness should be correlated with intelligence, social mobility, etc.

From an entertaining article in the Financial Times that develops the analogy between the interconnectedness of financial instruments and biological ecosystems.

“From an individual firm’s perspective, these strategies looked like sensible attempts to purge risk through diversification: more eggs are being placed in the basket,” says Mr Haldane. “Viewed across the system as a whole, however, it is clear now that these strategies generated the opposite result: the greater the number of eggs, the greater the fragility of the basket – and the greater the probability of bad eggs.”

That is what a mathematical ecologist would have predicted if he or she had known what was going on in the world of finance. The tropical rainforest, for example, has so many interdependent species that it is more vulnerable to an external shock than the simpler ecological diversity of savannahs and grasslands.

I wonder what prescription naturally arises from this perspective?  Total laissez-faire so that the financial system can suffer enough crashes, extinctions, and re-organizations to find a configuration that is stable for the long run?  Would we someday see Business schools sending missions out to shuttering financial institutions clamoring for intervention in the name of preserving derivative-diversity.  What is the analog of sexual reproduction and random genetic mixing?

Sex is a puzzle for evolutionary biologists.  It seems to be a waste of reproductive output.  A population of a fixed size which requires two members to produce offspring reproduces, and therefore grows, at half the rate of the same sized asexsual population (which requires only one member to produce one offspring.)

So to explain the prevalence of sexual reproduction in nature we need to find some advantage to offset this so-called two-fold cost of sex.  There are two prominent theories.  The first is that sexual reproduction allows a species to shed disadvantageous mutations.  Sexual reproduction thus ensures that offspring loses any harmful mutation with probability 1/2 (we are assuming that the parents do not have mutations of the same gene, a good approximation when there are many genes.)  But with asexual reproduction, these mutations just accumulate.

Another theory is that sexual reproduction, by mixing around genes, ensures genetic diversity which enables a species to survive changes in the environment.

Not Exactly Rocket Science reports on an experiment designed to test these theories.

Like humans, C.elegans has two sexes but unlike us, they are males and hermaphrodites (with males making up just one in every two thousand individuals).  Equipped with both sets of genitals, hermaphrodites worms can fertilise themselves without male help – far from being rude, telling C.elegans to go &$&! itself is a feasible lifestyle suggestion. Hermaphrodites could also mate with males, but they do that on less than one in 20 occasions.

The biologists manipulated the genetics of a population of these worms so that half would always mate with themselves and the others would always mate sexually.  Next, they exposed the worms to a chemical that raised their rate of mutations.  As the theory predicts, the sexually reproducing worms were more successful.

Next, they exposed the worms to a deadly bacterium.  Consistent with the second theory, the sexually reproducing worms also fared better in this experiment.

Now the big puzzle.  If sexual reproduction is beneficial, why do all sexually reproducing species in nature do it in pairs?  This paper by economists Motty Perry, Phil Reny, and Arthur Robson proves that, at least with respect to the harmful mutation theory, a particular form of tri-parental sex dominates bi-parental sex.   In the Perry-Reny-Robson world, reproduction requires two males and one female.  The offspring receives genes with half-probability from the mother and 1/4-probability from each of the fathers.

(With this particular menagerie, in every reproductive cycle each female gets two partners per encounter but each male gets two encounters.  Not only does this ensure that the “cost of sex” is again two-fold and not three-fold, but it also maintains equity in the gettin’ busy department.  Only fair.)

The Boston Globe has an interesting article about the unique playout of the creationist/Darwinist debate in the Islamic world.

Unlike in the West, creationist beliefs are not associated in the Muslim world with religious fundamentalism, but instead are often espoused by members of the mainstream intellectual elite – liberals, by their own lights, who see the expansive, scientific-sounding claims of creationism as tracing a middle way between the guidance of religion and the promise of modern science. Critics of the movement fear that this makes it more likely that creationism will find its way into policies there, especially when the theory of evolution is portrayed among Muslim thinkers, as it often is, as an instrument of Western intellectual hegemony.

That seems to be the thesis of this paper by neurobiologist Jerome Siegel:

Sleep can be seen as an adaptive state that benefits animals by increasing the efficiency of their activity. It does this by suppressing activity at times that have maximal predator risk and minimal opportunity for efficiently meeting vital needs, and by permitting activity at times of maximal food and prey availability and minimal predator risk.

I read this as arguing that if an animal is not sleeping it will do things that are not in its interest.  So sleep stops it from doing those things. Of course natural selection could instead have simply taught the animal not to do what’s against its self interest but instead, under this theory, sleep acts like a commitment device to blunt a self-control problem.

Via neuroskeptic.

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Let’s say you read a big book about recycling because you want to make an informed decision about whether it really makes sense to recycle.  The book is loaded with facts: some pro, some con.  You read it all, weigh the pluses and minuses and come away strongly convinced that recycling is a good thing.

But you are human and you can only remember so many facts.  You are also a good manager so you optimally allow yourself to forget all of the facts and just remember the bottom line that you were quite convinced that you should recycle.

This is a stylized version of how we set personal policies.  We have experiences, collect data, engage in debate and then come to conclusions.  We remember the conclusions but not always the reasons.  In most cases this is perfectly rational.  The details matter only insofar as they lead us to the conclusions so as long as we remember the conclusions, we can forget about the reasons.

It has consequences however.  How do you incorporate new arguments?  When your spouse presents arguments against recycling, the only response you have available is “yes, that’s true but still I know recycling is the right thing to do.”  And you are not just being stubborn.  You are optimally responding to your limited memory of the reasons you considered carefully in the past.

In fact, we are probably built with a heuristic that hard-wires this optimal memory management.  Call it cognitive-dissonance, confirmatory-bias, whatever.  It is an optimal response to memory constraints to set policies and then stubbornly stick to them.

Its easy to make up just-so stories to explain differences across siblings as being caused by birth-order.  This article casts doubt on the significance of birth order.

But we can ask the question of whether birth order should matter and in what ways.  Should natural selection imply systematic differences between older and younger siblings?  Here is one argument that it should.  Siblings “share genes” and as a consequence siblings have an evolutionary incentive to help each other.  Birth order creates an asymmetry in the ways that different siblings can help each other.  In particular, oldest siblings learn things first.  They are the first to experiment with different survival strategies.  The results of these experiments benefit all of the younger siblings.  (Am I a good hunter?  If so, my siblings are likely to be good hunters too.) Younger siblings have less to offer their older siblings on this dimension.

As a result we should expect older siblings to be more experimental than their younger siblings and more experimental than only children.

Here is evidence that older siblings have more years of education than younger siblings and more years of education than only children.

When animals move, forage or generally go about their lives, they provide inadvertent cues that can signal information to other individuals. If that creates a conflict of interest, natural selection will favour individuals that can suppress or tweak that information, be it through stealth, camouflage, jamming or flat-out lies. As in the robot experiment, these processes could help to explain the huge variety of deceptive strategies in the natural world.

The article at Not Exactly Rocket Science, describes an experiment in which robots competed for food at a hidden location and controlled a visible signal that could be used to reveal their location.  The robots adapted their signaling strategy by a process that simulates natural selection.  Eventually, the robots learned not to pay attention to others’ signals and the signals become essentially uninformative.

The financial markets are deregulated, banks are “too big to fail”, interest rates were kept low by Alan Greenspan etc…are these the only issues that caused the financial crisis?

Malcolm Gladwell has a very interesting article suggesting overconfidence played a role in causing the bubble that eventually burst.  The main protagonist in the story is Jimmy Cayne, former C.E.O. of Bear Stearns. The man was sometimes confident and perhaps over confident:

The high-water mark for Bear Stearns was 2003. The dollar was falling. A wave of scandals had just swept through the financial industry. The stock market was in a swoon. But Bear Stearns was an exception. In the first quarter of that year, its earnings jumped fifty-five per cent. Its return on equity was the highest on Wall Street. The firm’s mortgage business was booming. Since Bear Stearns’s founding, in 1923, it had always been a kind of also-ran to its more blue-chip counterparts, like Goldman Sachs and Morgan Stanley. But that year Fortune named it the best financial company to work for. “We are hitting on all 99 cylinders,’’ Jimmy Cayne told a reporter for the Times, in the spring of that year, “so you have to ask yourself, What can we do better? And I just can’t decide what that might be.’’ He went on, “Everyone says that when the markets turn around, we will suffer. But let me tell you, we are going to surprise some people this time around. Bear Stearns is a great place to be.’’

Gladwell connects overconfidence to success at some games people play in nature and refers to work by biological anthropologists.  This all seems quite interesting and I can see chasing it up for fun.  But he then goes on to try to connect Cayne’s overconfidence to his success at bridge – appreantly he is an excellent player and it helped him get his job at Bear Stearns.  This is a disconnect.  Bridge is a zero-sum game.  Behavioral biases such as overconfidence lead people to make mistakes and hence lose out more than people who judge hands correctly.  If Cayne is good at bridge, he must judge probabilities accurately rather than exaggerating his odds of success.  This then implies that he is less likely to be overconfident than others working in finance who are perhaps bad at bridge and poker as they are overaggressive.

So, while Gladwell may have a point to make, he does not do it convincingly as his main example concerns a protagonist who is less likely to be overconfident as he is good at zero-sum games.

Evolutionary Psychology and, increasingly, behavioral economics spin a lot of intriguing stories explaining foibles and otherwise mysterious behaviors as the byproduct of various tricks nature utilizes to get us to do her bidding.  I am on record in this blog as being a fan of this methodology.  But I also maintain a healthy skepticism and not just at the tendency to concoct “just-so” stories that often ask us to reformulate our theories of huge chunks of evolutionary history just to explain some nano-economic peculiarity.

Instead, when evaluating some theory of how emotions have evolved to induce us to behave in certain ways, skepticism should be aimed squarely at the basic premise.  The theory must come with a convincing explanation why nature would rely on a blunt instrument like emotions as opposed to all of the other tools at her disposal.  These questions seemed especially pressing when I read the following article about depression as a tool to blunt ambitions:

Dr Nesse’s hypothesis is that, as pain stops you doing damaging physical things, so low mood stops you doing damaging mental ones—in particular, pursuing unreachable goals. Pursuing such goals is a waste of energy and resources. Therefore, he argues, there is likely to be an evolved mechanism that identifies certain goals as unattainable and inhibits their pursuit—and he believes that low mood is at least part of that mechanism.

Why not a simpler mechanism:  just have us figure out that the goal is unattainable and (happily) go do something else? Don’t answer by saying that this emotional incentive mechanism evolved before our brains were advanced enough to do the calculation because the existence of an emotional response indicating the right course of action presupposes that this calculation is being made somewhere in the system.

Even granting that nature finds it convenient to do the calculation sub-(or un-)consciously and then communicate only the results to us, why using emotions?  Plants respond to incentives in the environment and they don’t need emotions to do it, presumably they are just programmed to change their “behavior” when conditions dictate.  Why would nature bother with such a messy, noisy, and indirect system of incentives rather than just give us neutral impulses?

Finally, you could try answering with the argument that evolution does not find optimal solutions, just solutions that work.  But that argument by itself can be made into a defense of everything and we are back to just-so stories.

De Waal’s own experiments suggest that capuchin monkeys are sensitive to fairness. If another monkey gets a tasty grape, they will not cooperate with an experimenter who offers a piece of cucumber (Nature, vol 425, p 297). A similar aversion has been spotted in dogs (New Scientist, 13 December 2008, p 12), and even rabbits seem affected by inequality, leading de Waal to believe that an ability to detect and react to injustice is common to all social animals. “Getting taken advantage of by others is a major concern in any cooperative system,” he says.

This article mostly just regurtitates some tired and fragile “evolutionary” explanations for fairness and revenge, but there are a few interesting tidbits, like some experiments with monkeys and this joke:

A genie appears to a man and says: “You can have anything you want. The only catch is that I’ll give your neighbour double.” The man says: “Take out one of my eyes.”

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