Evolutionary Psychology as Maladapted Psychology

Bolhuis reviews a book with the title of this post by philosopher Robert Richardson. (I have read a longer excellent book, "Adapting Minds", by philosopher David Buller. Here are some clips from the review:

Evolutionary psychology aims to apply evolutionary theory to the human mind. Specifically, it proposes that the mind consists of cognitive modules that evolved in response to selection pressures faced by our Stone Age ancestors. The approach has a wide popular appeal, perhaps because it often addresses such exciting topics as human desire, sex, and passion....Richardson readily acknowledges that our psychological capacities are evolved traits subject to natural selection. But at the same time, he maintains that there is very little we can find out about the evolution of the mind and that the evolutionary psychology interpretation is wrong from the perspective of evolutionary biology...he criticizes mainly the methods used by evolutionary psychologists, weighing the approach's theoretical framework using criteria from evolutionary biology...The main problem with evolutionary psychology is that it usually does not consider alternative explanations but takes the assumption of adaptation through natural selection as given.

Richardson rightly suggests that paleontologists are unlikely to unearth the evidence that can inform us about the social structure of our ancestral communities. I think one can go a step further. Even if we would be able to muster the evidence needed for an evolutionary psychological analysis of human cognition, it would not tell us anything about our cognitive mechanisms. The study of evolution is concerned with a historical reconstruction of traits. It does not, and cannot, address the mechanisms that are involved in the human brain. Those fall within the domains of neuroscience and cognitive psychology. In that sense, evolutionary psychology will never succeed, because it attempts to explain mechanisms by appealing to the history of these mechanisms. To use the author's words, "We might as well explain the structure of orchids in terms of their beauty." In this excellent book, Richardson shows very clearly that attempts at reconstruction of our cognitive history amount to little more than "speculation disguised as results." The book's title implies that the field is itself subject to selection pressure. Richardson is certainly piling it on.

Sex differences in judging attractiveness - brain correlates

When selecting mates, men place greater importance on attractiveness than do women, whereas women favor status and resources more so than men. The reasons behind these differences can be rationalized from both evolutionary and sociocultural perspectives. Cloutier et al use fMRI to examine the possibility that attractive faces of the opposite sex simply have different reward value for men and women. They show that brain reward circuits (nucleus accumbens [NAcc], orbito-frontal cortex [OFC]) exhibit a linear increase in activation with increased judgments of attractiveness. Their analysis further reveals sex differences in the recruitment of OFC, which distinguished attractive and unattractive faces only for male participants. In short, brain regions involved in identifying the potential reward value of a stimulus are more active when men view attractive women than when women view attractive men.


Figure - Axial sections display the left NAcc (top) and right NAcc (middle) and a sagittal section displays mOFC (bottom) spherical regions of interest superimposed on normalized anatomic images. Graphs to the right of each image display signal change (parameter estimates) for attractive and unattractive faces across female and male participants relative to the baseline fixation. Error bars indicate standard error of the mean. Activity in the left and right NAcc was greater for attractive than unattractive faces irrespective or the participants' sex. Activity in the mOFC exhibited an interaction between facial attractiveness and participant sex displaying greater activity for attractive than unattractive faces only for male participants.

MRI - the new phrenology

Having just done a posting on MRI, I thought it appropriate to point to a discussion by Michael Shermer in his "Skeptic" column in the Scientific American on the misuse and over-interpretation of MRI data.

It is a reminder that seeing scans with highlighted (usually in red) areas where your brain “lights up” when thinking about X (money, sex, God, and so on) should not seduce us into buying the Swiss Army knife model of the brain, with specialized modules for vision, language, facial recognition, cheating detection, risk taking, spirituality and even God. There is the minor problem of reversing the causal inference:

...where people see some activity in a brain area and then conclude that this part of the brain is where X happens. We can show that if I put you into a state of fear, your amygdala lights up, but that doesn’t mean that every time your amygdala lights up you are experiencing fear. Every brain area lights up under lots of different states. We just don’t have the data to tell us how selectively active an area is.

As Patricia Churchland points out:

Mental modules are complete nonsense. There are no modules that are encapsulated and just send information into a central processor. There are areas of specialization, yes, and networks maybe, but these are not always dedicated to a particular task.” Instead of mental module metaphors, let us use neural networks.

Bright light and good moods...

We are more agreeable when the light is brighter: here is the abstract, and one figure, from "Exposure to bright light is associated with positive social interaction and good mood over short time periods: A naturalistic study in mildly seasonal people" published in the Journal of Psychology:

Bright light is used to treat winter depression and might also have positive effects on mood in some healthy individuals. We examined possible links between bright light exposure and social interaction using naturalistic data. For 20 days in winter and/or summer, 48 mildly seasonal healthy individuals wore a light meter at the wrist and recorded in real-time their behaviours, mood, and perceptions of others during social interactions. Possible short-term effects of bright light were examined using the number of minutes, within any given morning, afternoon or evening, that people were exposed to light exceeding 1000 lux (average: 19.6 min). Social interactions were labelled as having occurred under conditions of no, low or high bright light exposure. Independent of season, day, time, and location, participants reported less quarrelsome behaviours, more agreeable behaviours and better mood when exposed to high but not low levels of bright light. Given that the effects were seen only when exposure levels were above average, a minimum level of bright light may be necessary for its positive effects to occur. Daily exposure levels were generally low in both winter and summer. Spending more time outdoors and improving indoor lighting may help optimize everyday social behaviour and mood across seasons in people with mild seasonality.

Figure - Quarrelsome behaviours (a) and agreeable behaviours (b) during time periods of no, low, or high levels of bright light exposure. Values are expressed as estimated least squares means of ipsatized frequencies, multiplied by a factor 100. Error bars represent standard errors of the mean. (* Significantly different from social interactions with low bright light exposure.)

Killer Instincts.

Dan Jones writes a news feature in Nature on neuroscientific and evolutionary perspectives on homicide, mainly carried out by men. Here are some selected chunks:

Men are not just more likely to kill other people than women are, they are also more likely to do so in groups ...Humans are not the only primates to form coalitions that kill members of neighbouring communities. ...five long-term study sites dotted around Africa have seen murderous 'gang violence' in chimpanzees...Wilson and Muller have compared death rates from conflict between groups of chimps in the five long-term study sites with data for inter-group human conflicts in numerous subsistence-farmer and hunter–gatherer societies...Overall, humans and chimpanzees showed comparable levels of violent death from aggression between groups...however, chimps display within group aggression and killing behaviour 200 times more frequently that aboriginal human groups...this prosocial lack of violence looks like a fundamental aspect of human nature — the human ability to generate in-group amity often goes hand in hand with out-group enmity...Choi and Bowles have produced models in which altruism and war co-evolve, promoting conflict between groups and greater harmony within them.

A decline in inter-personal violence (as opposed to inter-group war) can be seen over the shorter timescale and narrower field of modern European history. Eisner has documented a trend of declining homicide rates estimated from historical records left by coroners, royal courts and other official sources spanning Europe from the twelfth century to the modern day. After rising from an average of 32 homicides per 100,000 people per year in the thirteenth and fourteenth centuries to 41 in the fifteenth, the murder rate has steadily dropped in every subsequent century, to 19, 11, 3.2, 2.6 and finally 1.4 in the twentieth century...a few centuries is too short a time for evolution to have shaped human nature much... A part of the answer that is consistent with an evolutionary approach is a long-term reduction in inequalities of life circumstances and prospects.

The Best Men Are (Not Always) Already Taken

Bressan1 and Stranieri take a (dubious) evolutionary psychological approach to the question of female preference for single versus attached males. The outcome is interesting. Here is their abstract:

Because men of higher genetic quality tend to be poorer partners and parents than men of lower genetic quality, women may profit from securing a stable investment from the latter, while obtaining good genes via extrapair mating with the former. Only if conception occurs, however, do the evolutionary benefits of such a strategy overcome its costs. Accordingly, we predicted that (a) partnered women should prefer attached men, because such men are more likely than single men to have pair-bonding qualities, and hence to be good replacement partners, and (b) this inclination should reverse when fertility rises, because attached men are less available for impromptu sex than single men. In this study, 208 women rated the attractiveness of men described as single or attached. As predicted, partnered women favored attached men at the low-fertility phases of the menstrual cycle, but preferred single men (if masculine, i.e., advertising good genetic quality) when conception risk was high.

Evolutionary psychology on steroids...

Here are Steven Pinker's comments on recent data showing that the human genome has undergone strong recent selection, rendering invalid evolutionary psychology's initial assumption that human evolution halted 10,000 - 50,000 years ago.

New results from the labs of Jonathan Pritchard, Robert Moyzis, Pardis Sabeti, and others have suggested that thousands of genes, perhaps as much as ten percent of the human genome, have been under strong recent selection, and the selection may even have accelerated during the past several thousand years. The numbers are comparable to those for maize, which has been artificially selected beyond recognition during the past few millennia.

If these results hold up, and apply to psychologically relevant brain function (as opposed to disease resistance, skin color, and digestion, which we already know have evolved in recent millennia), then the field of evolutionary psychology might have to reconsider the simplifying assumption that biological evolution was pretty much over and done with 10-000 — 50,000 years ago.

And if so, the result could be evolutionary psychology on steroids. Humans might have evolutionary adaptations not just to the conditions that prevailed for hundreds of thousands of years, but also to some of the conditions that have prevailed only for millennia or even centuries. Currently, evolutionary psychology assumes that any adaptation to post-agricultural ways of life are 100% cultural.

Though I suspect some revisions will be called for, I doubt they will be radical, for two reasons. One is that many aspects of the human (and ape) environments have been constant for a much longer time than the period in which selection has recently been claimed to operate. Examples include dangerous animals and insects, toxins and pathogens in spoiled food and other animal products, dependent children, sexual dimorphism, risks of cuckoldry and desertion, parent-offspring conflict, risk of cheaters in cooperation, fitness variation among potential mates, causal laws governing solid bodies, presence of conspecifics with minds, and many others. Recent adaptations would have to be an icing on this cake -- quantitative variations within complex emotional and cognitive systems.

The other is the empirical fact that human races and ethnic groups are psychologically highly similar, if not identical. People everywhere use language, get jealous, are selective in choosing mates, find their children cute, are afraid of heights and the dark, experience anger and disgust, learn names for local species, and so on. If you adopt children from a technologically undeveloped part of the world, they will fit in to modern society just fine. To the extent that this is true, there can't have been a whole lot of uneven psychological evolution postdating the split among the races 50-100,000 years ago (though there could have been parallel evolution in all the branches).

More on the evils of multitasking.

In a comment below, MindBlog reader Gregory points to a great article in the Atlantic on the toxic mental effects of multitasking. I wanted to bring the link into this separate post so that more of you will see it. It is by culture/technology commentator Walter Kirn:

Neuroscience is confirming what we all suspect: Multitasking is dumbing us down and driving us crazy. One man’s odyssey through the nightmare of infinite connectivity

...Multitasking messes with the brain in several ways. At the most basic level, the mental balancing acts that it requires—the constant switching and pivoting—energize regions of the brain that specialize in visual processing and physical coordination and simultaneously appear to shortchange some of the higher areas related to memory and learning. We concentrate on the act of concentration at the expense of whatever it is that we’re supposed to be concentrating on.

What does this mean in practice? Consider a recent experiment at UCLA, where researchers asked a group of 20-somethings to sort index cards in two trials, once in silence and once while simultaneously listening for specific tones in a series of randomly presented sounds. The subjects’ brains coped with the additional task by shifting responsibility from the hippocampus—which stores and recalls information—to the striatum, which takes care of rote, repetitive activities. Thanks to this switch, the subjects managed to sort the cards just as well with the musical distraction—but they had a much harder time remembering what, exactly, they’d been sorting once the experiment was over.

Even worse, certain studies find that multitasking boosts the level of stress-related hormones such as cortisol and adrenaline and wears down our systems through biochemical friction, prematurely aging us. In the short term, the confusion, fatigue, and chaos merely hamper our ability to focus and analyze, but in the long term, they may cause it to atrophy.

The next generation, presumably, is the hardest-hit. They’re the ones way out there on the cutting edge of the multitasking revolution, texting and instant messaging each other while they download music to their iPod and update their Facebook page and complete a homework assignment and keep an eye on the episode of The Hills flickering on a nearby television.

Pinker et al. on the logic of indirect speech.

Pinker, Nowak, and Lee do an interesting perspectives article in PNAS that looks more rigorously at why we don't just blurt out what we mean, as in:

- Would you like to come up and see my etchings? [a sexual come-on]
- If you could pass the guacamole, that would be awesome. [a polite request]
- Nice store you got there. Would be a real shame if something happened to it. [a threat]
- We're counting on you to show leadership in our Campaign for the Future. [a solicitation for a donation]
- Gee, officer, is there some way we could take care of the ticket here? [a bribe]

Here is their abstract:

When people speak, they often insinuate their intent indirectly rather than stating it as a bald proposition. Examples include sexual come-ons, veiled threats, polite requests, and concealed bribes. We propose a three-part theory of indirect speech, based on the idea that human communication involves a mixture of cooperation and conflict. First, indirect requests allow for plausible deniability, in which a cooperative listener can accept the request, but an uncooperative one cannot react adversarially to it. This intuition is supported by a game-theoretic model that predicts the costs and benefits to a speaker of direct and indirect requests. Second, language has two functions: to convey information and to negotiate the type of relationship holding between speaker and hearer (in particular, dominance, communality, or reciprocity). The emotional costs of a mismatch in the assumed relationship type can create a need for plausible deniability and, thereby, select for indirectness even when there are no tangible costs. Third, people perceive language as a digital medium, which allows a sentence to generate common knowledge, to propagate a message with high fidelity, and to serve as a reference point in coordination games. This feature makes an indirect request qualitatively different from a direct one even when the speaker and listener can infer each other's intentions with high confidence.

Terror alerts kill more people than terrorists in the US?

I have long held the opinion, reinforced by this article in the NYTimes, that the absurd terror alert system devised by the department of "homeland security" kills more people than the potential terrorist threat, given that "the chances of the average person dying in America at the hands of international terrorists to be comparable to the risk of dying from eating peanuts, being struck by an asteroid or drowning in a toilet." The article describes studies on a cohort of 2,700 people studied before and after the Sept. 11 attack which indicate a correlation (which is not a cause) between expressed anxiety over a terrorist attack and subsequent cardiovascular ailments.

Coevolution of choosiness and cooperation

An interesting modeling article by McNamara et al. suggests a novel evolutionary mechanism based on a positive coevolutionary feedback between cooperativeness and choosiness. If individuals vary in their degree of cooperativeness, and if they can decide whether or not to continue interacting with each other on the basis of their respective levels of cooperativeness, then cooperation can gradually evolve from an uncooperative state. When an individual's cooperativeness is used by other individuals as a choice criterion, there can be competition to be more generous than others (competetive altruism). The evolution of cooperation between non-relatives can then be driven by a positive feedback between increasing levels of cooperativeness and choosiness. In this model, individual behavioural differences are the key to the evolution of cooperation. Because the model does not invoke complex mechanisms such as negotiation behaviour, it can be applied to a wide range of species.

The model calculations use an infinite population where, in each of a discrete series of time steps (rounds), pairs of individuals engage in a game that can be described as a social dilemma. Each individual is characterized by two traits: a cooperativeness trait x, which specifies the amount of effort that the individual devotes to generating benefits available (at least in part) to its co-player; and a choosiness trait y, which specifies the minimum degree of cooperativeness that the focal individual is prepared to accept from its co-player. The traits x and y are genetically determined and are not adjusted in response to the co-player's behaviour. Thus, unlike in many models in which flexible effort adjustment is a key ingredient1, individuals in their model are consistent in their degree of cooperativeness.

Planned Obsolescence? The Four-Year Itch

Helen Fisher, author of "Why We Love" and an anthropology professor at Rutgers, has written a brief essay with the title of this post. She did a cross cultural survey of when divorces occur and found that divorces regularly peaked during and around the fourth year after wedding (no evidence for the commonly assumed seven year itch indicated in the graphic). Divorces peaked among couples in their late twenties. And the more children a couple had, the less likely they were to divorce: some 39% of worldwide divorces occurred among couples with no dependent children; 26% occurred among those with one child; 19% occurred among couples with two children; and 7% of divorces occurred among couples with three young. In trying to figure out so many men and women divorce during and around the 4-year mark; at the height of their reproductive years; and often with a single child, she had an "a ha" moment:

Women in hunting and gathering societies breastfeed around the clock, eat a low-fat diet and get a lot of exercise — habits that tend to inhibit ovulation. As a result, they regularly space their children about four years apart. Thus, the modern duration of many marriages—about four years—conforms to the traditional period of human birth spacing, four years.

Perhaps human parental bonds originally evolved to last only long enough to raise a single child through infancy, about four years, unless a second infant was conceived. By age five, a youngster could be reared by mother and a host of relatives. Equally important, both parents could choose a new partner and bear more varied young.

Her theory fits with data on other species:

Only about three percent of mammals form a pairbond to rear their young. Take foxes. The vixen's milk is low in fat and protein; she must feed her kits constantly; and she will starve unless the dog fox brings her food. So foxes pair in February and rear their young together. But when the kits leave the den in mid summer, the pairbond breaks up. Among foxes, the partnership lasts only through the breeding season. This pattern is common in birds. Among the more than 8,000 avian species, some 90% form a pairbond to rear their young. But most do not pair for life. A male and female robin, for example, form a bond in the early spring and rear one or more broods together. But when the last of the fledgling fly away, the pairbond breaks up... Like pair-bonding in many other creatures, humans have probably inherited a tendency to love and love again—to create more genetic variety in our young.

Experimental Philosophy - moving out of the armchair?

The Dec. 9 New York Times Magazine has a fascinating article by Kwame Appiah that I have been meaning to mention, on the new philosophical trend of designing explicit experiments - many to probe the classic philosophical concept of intentionality. The following sort of result is now called the "Knobe effect" after the philosophy graduate student who devised the experiment (and the article describes a number of further experiments):

Suppose the chairman of a company has to decide whether to adopt a new program. It would increase profits and help the environment too. “I don’t care at all about helping the environment,” the chairman says. “I just want to make as much profit as I can. Let’s start the new program.” Would you say that the chairman intended to help the environment?

O.K., same circumstance. Except this time the program would harm the environment. The chairman, who still couldn’t care less about the environment, authorizes the program in order to get those profits. As expected, the bottom line goes up, the environment goes down. Would you say the chairman harmed the environment intentionally?

I don’t know where you ended up, but in one survey, only 23 percent of people said that the chairman in the first situation had intentionally helped the environment. When they had to think about the second situation, though, fully 82 percent thought that the chairman had intentionally harmed the environment. There’s plenty to be said about these interestingly asymmetrical results.

... is it a good thing that we attribute intention in the curious way that we do, and if so, why? (Is the Knobe effect a bug or a feature?) You can conduct more research to try to clarify matters, but you’re left having to interpret the findings; they don’t interpret themselves. There always comes a point where the clipboards and questionnaires and M.R.I. scans have to be put aside. To sort things out, it seems, another powerful instrument is needed. Let’s see — there’s one in the corner, over there. The springs are sagging a bit, and the cushions are worn, but never mind. That armchair will do nicely.

Evolutionary origins of dance and art...

Natalie Angier does a fascinating piece on evolutionary perspectives on how human dance and art originated. Here are some (slightly edited) clips from her article in the Nov. 27 NY Times science section (whole text here), which emphasize the work of Ellen Dissanayake, an independent scholar affiliated with the University of Washington:

...the creative drive has all the earmarks of being an adaptation on its own. The making of art consumes enormous amounts of time and resources, an extravagance you wouldn’t expect of an evolutionary afterthought. Art also gives us pleasure, she said, and activities that feel good tend to be those that evolution deems too important to leave to chance.

What might that deep-seated purpose of art-making be? Geoffrey Miller and other theorists have proposed that art serves as a sexual display, a means of flaunting one’s talented palette of genes... Ms. Dissanayake has other ideas. To contemporary Westerners, she said, art may seem detached from the real world, an elite stage on which proud peacocks and designated visionaries may well compete for high stakes. But among traditional cultures and throughout most of human history, she said, art has also been a profoundly communal affair, of harvest dances, religious pageants, quilting bees, the passionate town rivalries that gave us the spires of Chartres, Reims and Amiens...engaging in what Ms. Dissanayake calls “artifying,” people can be quickly and ebulliently drawn together, and even strangers persuaded to treat one another as kin. Through the harmonic magic of art, the relative weakness of the individual can be traded up for the strength of the hive, cohered into a social unit ready to take on the world.

She suggests that many of the basic phonemes of art, the stylistic conventions and tonal patterns, the mental clay, staples and pauses with which even the loftiest creative works are constructed, can be traced back to the most primal of collusions — the intimate interplay between mother and child.

After studying hundreds of hours of interactions between infants and mothers from many different cultures, Ms. Dissanayake and her collaborators have identified universal operations that characterize the mother-infant bond. They are visual, gestural and vocal cues that arise spontaneously and unconsciously between mothers and infants, but that nevertheless abide by a formalized code: the calls and responses, the swooping bell tones of motherese, the widening of the eyes, the exaggerated smile, the repetitions and variations, the laughter of the baby met by the mother’s emphatic refrain. The rules of engagement have a pace and a set of expected responses, and should the rules be violated, the pitch prove too jarring, the delays between coos and head waggles too long or too short, mother or baby may grow fretful or bored.

To Ms. Dissanayake, the tightly choreographed rituals that bond mother and child look a lot like the techniques and constructs at the heart of much of our art. “These operations of ritualization, these affiliative signals between mother and infant, are aesthetic operations, too,” she said in an interview. “And aesthetic operations are what artists do. Knowingly or not, when you are choreographing a dance or composing a piece of music, you are formalizing, exaggerating, repeating, manipulating expectation and dynamically varying your theme.” You are using the tools that mothers everywhere have used for hundreds of thousands of generations.

In art, as in love, as in dancing the hora, if you don’t know the moves, you really can’t fake them.

How our brains process inequity in rewards.

This work suggests that the calculation of social standing - as indexed by payment - may be an unconscious and automatic process in the brain. The previous post on monkeys judging inequity in rewards suggests an evolutionary origin in earlier primate behavior. Here we have a very similar experiment done on humans, with fMRI data that we can't get from the monkeys. The results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain. Several studies show that most of us place as much value on relative remuneration, comparing ourselves with others, as on its absolute level. In the current work, when subjects were given different compensation for solving the same puzzle, this was reflected by different activation levels in the ventral striatum, a brain region known to be involved in the comparison of predicted and actually received rewards (i.e., reward prediction error). Here is the abstract from Fliessbach et al., followed by a figure from the paper:

Whether social comparison affects individual well-being is of central importance for understanding behavior in any social environment. Traditional economic theories focus on the role of absolute rewards, whereas behavioral evidence suggests that social comparisons influence well-being and decisions. We investigated the impact of social comparisons on reward-related brain activity using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject's payment affects blood oxygenation level–dependent responses in the ventral striatum. Our results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain.

Figure - Glassbrain projection of brain regions showing stronger BOLD responses in conditions in which a subject received a reward while the other did not compared with conditions in which a subject did not receive a reward at all.

Monkeys judge inequity like humans

DeWaal and collaborators expand on previous observations to show that capuchin monkeys get really pissed off if they worked harder for a reward than another monkey, and then see that monkey get a greater reward! This suggests that our human resentment of inequity in rewards my have a very ancient origin in primate behavior. Here is their abstract:

Without joint benefits, joint actions could never have evolved. Cooperative animals need to monitor closely how large a share they receive relative to their investment toward collective goals. This work documents the sensitivity to reward division in brown, or tufted, capuchin monkeys (Cebus apella). In addition to confirming previous results with a larger subject pool, this work rules out several alternative explanations and adds data on effort sensitivity. Thirteen adult monkeys exchanged tokens for rewards, showing negative reactions to receiving a less-favored reward than their partner. Because their negative reaction could not be attributed to the mere visibility of better rewards (greed hypothesis) nor to having received such rewards in the immediate past (frustration hypothesis), it must have been caused by seeing their partner obtain the better reward. Effort had a major effect in that by far the lowest level of performance in the entire study occurred in subjects required to expend a large effort while at the same time seeing their partner receive a better reward. It is unclear whether this effort–effect was based on comparisons with the partner, but it added significantly to the intensity of the inequity response. These effects are as expected if the inequity response evolved in the context of cooperative survival strategies.

Coevolution of Parochial Altruism and War

Choi and Bowles offer an interesting game theoretic analysis that suggests why the combination of loyalty towards one's own group and hostility towards outsiders seems to be such a fixed constant of human societies. Here is their abstract:

Altruism—benefiting fellow group members at a cost to oneself—and parochialism—hostility toward individuals not of one's own ethnic, racial, or other group—are common human behaviors. The intersection of the two—which we term "parochial altruism"—is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one's payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

A review by Arrow explains the simulation:

In Choi and Bowles' simulation, 20 small groups of agents interact over thousands of generations. Agents have two genes, each with two alleles. They are either tolerant (T) or parochial (P) and either altruistic (A) or not (N). Offspring inherit their parents'traits, with occasional random mutations. Altruists help fellow group members at a personal cost; non-altruists do not. Tolerant agents have lucrative exchanges with outsiders; parochial agents do not. A high proportion of parochials in groups restricts trading opportunities for all....The societies that evolve are stable in two conditions: when either selfish traders (TN) or generous warriors (PA) are the dominant type. A few PN bullies and even fewer TA philanthropists can coexist within trader or warrior regimes. The trading regime is peaceful. Standoffs and wars are more common in the warrior regime, but even infrequent war--10 to 20% of encounters--can maintain high levels of parochial altruism. Similar findings for the impact of intermittent war on the evolution of heroism (6) suggest that war need not be "constant" to act as a powerful selective force...The convergence of altruism and parochialism in Choi and Bowles' simulation is consistent with links between the two found in behavioral studies. Selfish choices in social dilemma experiments, for example, diminish markedly when the game is embedded in an intergroup context.

Facts are no match for gossip...

In yesterday's Science NY Times, John Tierny describes work by Ralf D. Sommerfeld and colleagues on human reciprocity that has a surprising result (PDF here). Here are some clips:

Language, according to the anthropologist Robin Dunbar, evolved because gossip is a more efficient version of the “social grooming” essential for animals to live in groups...Gossip also told people whom to trust, and the prospect of a bad reputation discouraged them from acting selfishly, so large groups could peacefully cooperate. At least, that was the theory: gossip promoted the “indirect reciprocity” that made human society possible.

To test it, researchers at the Max Planck Institute for Evolutionary Biology and the University of Vienna gave 10 Euros apiece to 126 students and had them play a game that put them in a dilemma. On each turn, the players would be paired off, and one of them was offered a chance to give 1.25 Euros to the other. If he agreed, the researchers added a bonus of .75 Euro so that the recipient ended up gaining 2 Euros...If the first player refused to give the money, he’d save 1.25 Euros, but if others found out about his miserliness they might later withhold money from him. As the game progressed, with the players changing partners frequently and alternating between the donor and recipient roles, the players were given information about their partners’ past decisions...Sometimes the donor was shown a record of what the partner had done previously while playing the donor role. The more generous this partner had earlier been toward other players, the more likely the donor was to give him something...Sometimes the donor was shown gossip about the partner from another player. When the partner was paid a compliment like “spendabler spieler!” — generous player! — the donor was more likely to give money. But the donor turned stingy when he saw gossip like “übler geizkragen” — nasty miser.

So far, so good. As predicted, gossip promoted indirect reciprocity. The research, published in the Proceedings of the National Academy of Sciences [Note, I haven't found this article yet in a PNAS search], showed that most people passed on accurate gossip and used it for the common good. They rewarded cooperative behavior even when they themselves weren’t directly affected by the behavior...If a cooperation game like this was played without consequences for the players’ reputations — as has been done in other experiments — most players would be miserly, and cooperation would collapse. In this experiment they were generous most of the time, and on average ended up with twice as much money as they had at the beginning of the game.

But here’s the disconcerting news from the experiment. In a couple of rounds, each donor was given both hard facts and gossip. He was given a record of how his partner had behaved previously as well as some gossip — positive gossip in one round, negative in another...The donor was told that the source of the gossip didn’t have any extra information beyond what the donor could already see for himself. Yet the gossip, whether positive or negative, still had a big influence on the donors’ decisions, and it didn’t even matter if the source of the gossip had a good reputation himself. On average, cooperation increased by about 20 percent if the gossip was good, and fell by 20 percent if the gossip was negative.

Why is this?

It could be,” Sommerfeld suggested, “that we are just more adapted to listen to other information than to observe people, because most of the time we’re not able to observe how other people are behaving. Thus we might believe we have missed something."

Some rambling on "Selves" and "Purpose"

The recent posts on Alwyn Scott and the Blakesless' book prompt me to this random walk....

Self conscious "Purpose" of the sort we humans experience, in the service of crafting new political movements or environments, is an evolved psychology that (sometimes) helps pass on our genes, and requires our distinctively human self reflective "I". Our behavior and that of other animals also reflects a kind of purpose that has been formed by our evolutionary and developmental history. In other animals such behaviors are acted out on the cusp of an eternal present - there is no evidence that they "know that they know" in the way that we can.

Both modern neuroscience (cf. the quote from the Blakesless' book) and Buddhist psychology inform us that the self and the purpose that each of us experiences is an illusion or confabulation of our brains - hopefully a useful one - whose utility is tested by how it enhances our energy and individual survival. This 'illusion' is a powerful instrument of downward causation, regulating our psychological, immune, neuro-endocrine robustness.

What is especially amazing is that our human body/brain can sometimes use meditative or other techniques to bootstrap to a level of metacognition that rests antecedent to - and can be the detached observer of - the generation of this illusion of a self and its purposes.

The maximum power of our self illusion, for most of us, goes with our heartfelt immersion and belief in it (i.e., our delusion). From such a immersion, it can be more difficult to discern or appreciate the different selves and purposes of other humans, and their cultures and historical eras.

Moral Universals

Nicholas Wade offers a summary (PDF here) of some of the evidence that humans have an evolved moral intuition that appeared before the development of language. (This has been the subject of several previous blog posts), focusing on the views of Jonathan Haidt. Haidt suggests that there are five innate moral systems, or rather, innate psychological mechanisms that predispose children to absorb certain virtues. Some concern the protection of individuals, others the ties that bind a group together. Of the moral systems that protect individuals, one is concerned with preventing harm to the person and the other with reciprocity and fairness. Less familiar are the three systems that promote behaviors developed for strengthening the group. These are loyalty to the in-group, respect for authority and hierarchy, and a sense of purity or sanctity.

A striking demonstration comes from experiments that show that people will say it is morally acceptable to pull a switch that diverts a train, killing just one person instead of the five on the other track. But if asked to save the same five lives by throwing a person in the train’s path, people will say the action is wrong. This may be evidence for an ancient subconscious morality that deters causing direct physical harm to someone else. An equally strong moral sanction has not yet evolved for harming someone indirectly.