Globalization and the internet enhance world cooperation...

Buchan et al. tabulate the relationship between a country-level globalization index (CGI) produced by the Centre for the Study of Globalization and Regionalisation at the University of Warwick, U.K and the results of a game experiment carried out 190 study participants from Columbus (Ohio, U.S.), Milan (Italy), Kazan (Tatarstan, Russia), Buenos Aires (Argentina), Johannesburg (South Africa), Tehran (Iran), and in surrounding areas. In the game (rather involved, here is a PDF describing the details), participants (who are randomly matched with 8 others from other countries and 4 local people) distribute cash tokens between 'personal', 'local', and 'world' envelopes in a sequential series of decisions that result in varying rewards depending on how many other local and other country participants give matched contributions to their local and world envelopes. Their finding and conclusion:

...as country and individual levels of globalization increase, so too does individual cooperation at the global level vis-à-vis the local level. In essence, “globalized” individuals draw broader group boundaries than others, eschewing parochial motivations in favor of cosmopolitan ones. Globalization may thus be fundamental in shaping contemporary large-scale cooperation and may be a positive force toward the provision of global public goods.

As the authors describe their nested world decision game:

A participant (Individual I) may allot the money to his or her Personal account and/or allot it to his or her Local or World group account. The 3 numbers in brackets [x, y, z] represent the returns to I (x), to another person from I's local group (y), and to a person from a different country (z) from a token allotted to I's Personal, Local, or World account, respectively. That is, a token allotted to the Personal account (dotted line) gives 1 token to I and nothing to anyone else. A token allotted to the Local account (dashed line) yields half a token to all of the 3 members of I's Local account but nothing to the people from the other two Local groups. A token allotted to I's World account (solid line) yields a quarter of a token to all of the 12 people in the World group.



Figure - Relationship between CGI and mean Allocations to World and Local Accounts. Countries are plotted according to their macrolevel globalization score on the x axis and mean aggregate levels of contribution to the World account (diamond points), and Local accounts (square points) on the y axis. The linear predictions for both variables are also plotted.

Globalization and the internet diminish cooperation.

As a partial counter to today's other MindBlog posting, a Kristoff essay, "The Daily Me," argues that we use the internet for interactions that confirm and enhance our existing attitudes, thus diminishing the prospect of cooperation or agreement with people who hold different views:

When we go online, each of us is our own editor, our own gatekeeper. We select the kind of news and opinions that we care most about....Nicholas Negroponte of M.I.T. has called this emerging news product The Daily Me. And if that’s the trend, God save us from ourselves...That’s because there’s pretty good evidence that we generally don’t truly want good information — but rather information that confirms our prejudices. We may believe intellectually in the clash of opinions, but in practice we like to embed ourselves in the reassuring womb of an echo chamber.

One of last year’s more fascinating books was Bill Bishop’s “The Big Sort: Why the Clustering of Like-Minded America is Tearing Us Apart.” He argues that Americans increasingly are segregating themselves into communities, clubs and churches where they are surrounded by people who think the way they do...The nation grows more politically segregated — and the benefit that ought to come with having a variety of opinions is lost to the righteousness that is the special entitlement of homogeneous groups...The result is polarization and intolerance.

Why jokes are hard to remember.

Natalie Angier has a nice piece on foibles of our memory in last Tuesday's science section of the NYTimes. Some edited clips:

The ease with which people forget jokes is one of those quirks...that ends up revealing a surprising amount about the underlying architecture of memory....We have our version of a buffer...a short-term working memory of limited scope and fast turnover rate...our equivalent of a save button: the hippocampus, deep in the forebrain is essential for translating short-term memories into a more permanent form...what really distinguishes the lasting from the transient is how strongly the memory is engraved in the brain...The deeper the memory, the more readily and robustly an ensemble of like-minded neurons will fire...A simple melody with a simple rhythm and repetition can be a tremendous mnemonic device...It would be a virtually impossible task for young children to memorize a sequence of 26 separate letters if you just gave it to them as a string of information, but when the alphabet is set to the tune of the ABC song with its four melodic phrases, preschoolers can learn it with ease.

Really great jokes, on the other hand, punch the lights out of do re mi. They work not by conforming to pattern recognition routines but by subverting them...Jokes work because they deal with the unexpected, starting in one direction and then veering off into another...What makes a joke successful are the same properties that can make it difficult to remember.

As frustrating as it can be to forget something new, it’s worse to forget what you already know... Behind the tying up of tongues are the too-delicate nerves of our brain’s frontal lobes and their sensitivity to anxiety and the hormones of fight or flight. The frontal lobes that rifle through stored memories and perform other higher cognitive tasks tend to shut down when the lower brain senses danger and demands that energy be shunted its way....For that reason anxiety can be a test taker’s worst foe.

Pride: Adaptive Social Emotion or Seventh Sin?

The title of this post is taken from a tidy little article by Williams and DeSteno who perform a very simple manipulation to boost the pride (self esteem) of some of the participants in an experiment (telling them they have scored brilliantly on a previous test of visuospatial acuity regardless of their actual score), finding that they then take a dominant role within a subsequent group problem-solving task (working together on a three-dimensional puzzle), and also are perceived as the most likeable interaction partners. Here is their abstract:

This experiment examined the ability of pride to serve as an adaptive emotion within the context of social interaction. After an in vivo induction of pride or a neutral state, participants engaged in a group problem-solving task. In contrast to a conventional view that pride is often associated with negative interpersonal outcomes, results confirmed that proud individuals not only took on a dominant role within the group problem-solving task, but also were perceived as the most likeable interaction partners. These findings suggest that pride, when representing an appropriate response to actual performance (as opposed to overgeneralized hubris), constitutes a functional social emotion with important implications for leadership and the building of social capital.

Musical training enhances detection of emotional components of speech.

As a followup to my Feb. 25 post, I pass on work by Kraus and collaborators at Northwestern Univ. in which they tested 30 young adults in three categories: those with no musical training, those who started learning to play a musical instrument before age 7, and those who started later but had at least 10 years of training. The scientists hooked them up to electrodes that recorded the response of the auditory brainstem to a quarter-second of an emotion-laden sound: an infant's wail (see the figure below). The subjects with the most musical experience responded the fastest to the sound. with those who had practiced since early childhood having the strongest response to the parts of the cry for which timing, pitch, and timbre were most complex. Non-musicians did not pick up on fine-grained information in the signal.
Here is their abstract, followed by a figure:

Musicians exhibit enhanced perception of emotion in speech, although the biological foundations for this advantage remain unconfirmed. In order to gain a better understanding for the influences of musical experience on neural processing of emotionally salient sounds, we recorded brainstem potentials to affective human vocal sounds. Musicians showed enhanced time-domain response magnitude to the most spectrally complex portion of the stimulus and decreased magnitude to the more periodic, less complex portion. Enhanced phase-locking to stimulus periodicity was likewise seen in musicians' responses to the complex portion. These results suggest that auditory expertise engenders both enhancement and efficiency of subcortical neural responses that are intricately connected with acoustic features important for the communication of emotional states. Our findings provide the first biological evidence for behavioral observations indicating that musical training enhances the perception of vocally expressed emotion in addition to establishing a subcortical role in the auditory processing of emotional cues.


Fig. 1. Stimulus and grand average response waveforms. Response waveforms have been shifted back in time (∼7 msec) to align the stimulus and response onsets. Boxes delineate two stimulus subsections and the corresponding brainstem responses. The first subsection (112–142 ms) corresponds to the periodic portion and the second (145–212 ms) corresponds to the more complex portion. (A) Stimulus time-amplitude waveform. (B) Stimulus spectrogram. The stimulus F₀ is superimposed as a highlighted line (∼280 Hz, left axis) with higher frequency spectral components plotted between white dotted lines (right axis). Although the F₀ is detectable during the first section, the greater acoustic complexity of the second section results in the inability of the sound analyzing software (Praat) to track the F₀. The harmonics are likewise more aperiodic. (C) The averaged responses of MusYrs and NonMus. Major peaks (β, 1 and 2) are labeled above the waveform.

A model for the outbreak of cooperation.

Helbing and Yu, in an open access article, offer a fascinating game theoretic model that turns defectors into cooperators. The trick is to incorporate success-driven migration. The graphic illustrations are interesting and clear, and I suggest you check them out. Here is their abstract:

According to Thomas Hobbes' Leviathan [1651; 2008 (Touchstone, New York), English Ed], “the life of man [is] solitary, poor, nasty, brutish, and short,” and it would need powerful social institutions to establish social order. In reality, however, social cooperation can also arise spontaneously, based on local interactions rather than centralized control. The self-organization of cooperative behavior is particularly puzzling for social dilemmas related to sharing natural resources or creating common goods. Such situations are often described by the prisoner's dilemma. Here, we report the sudden outbreak of predominant cooperation in a noisy world dominated by selfishness and defection, when individuals imitate superior strategies and show success-driven migration. In our model, individuals are unrelated, and do not inherit behavioral traits. They defect or cooperate selfishly when the opportunity arises, and they do not know how often they will interact or have interacted with someone else. Moreover, our individuals have no reputation mechanism to form friendship networks, nor do they have the option of voluntary interaction or costly punishment. Therefore, the outbreak of prevailing cooperation, when directed motion is integrated in a game-theoretical model, is remarkable, particularly when random strategy mutations and random relocations challenge the formation and survival of cooperative clusters. Our results suggest that mobility is significant for the evolution of social order, and essential for its stabilization and maintenance.

Empathy modulated by genetic background.

In mice, to be sure, but if this is like so many other genetics/behavior studies in mice, the same observations will probably soon be made in humans.

Empathy, as originally defined, refers to an emotional experience that is shared among individuals. When discomfort or alarm is detected in another, a variety of behavioral responses can follow, including greater levels of nurturing, consolation or increased vigilance towards a threat. Moreover, changes in systemic physiology often accompany the recognition of distressed states in others. Employing a mouse model of cue-conditioned fear, we asked whether exposure to conspecific distress influences how a mouse subsequently responds to environmental cues that predict this distress. We found that mice are responsive to environmental cues that predict social distress, that their heart rate changes when distress vocalizations are emitted from conspecifics, and that genetic background substantially influences the magnitude of these responses. Specifically, during a series of pre-exposure sessions, repeated experiences of object mice that were exposed to a tone-shock (CS-UCS) contingency resulted in heart rate deceleration in subjects from the gregarious C57BL/6J (B6) strain, but not in subjects from the less social BALB/cJ (BALB) strain. Following the pre-exposure sessions, subjects were individually presented with the CS-only for 5 consecutive trials followed by 5 consecutive pairings of the CS with the UCS. Pre-exposure to object distress increased the freezing responses of B6 mice, but not BALB mice, on both the CS-only and the CS-UCS trials. These physiological and behavioral responses of B6 mice to social distress parallel features of human empathy. Our paradigm thus has construct and face validity with contemporary views of empathy, and provides unequivocal evidence for a genetic contribution to the expression of empathic behavior.

Neural correlates of aesthetic preference - differences between men and women

The abstract from Cela-Condea et al.:

The capacity to appreciate beauty is one of our species' most remarkable traits. Although knowledge about its neural correlates is growing, little is known about any gender-related differences. We have explored possible differences between men and women's neural correlates of aesthetic preference. We have used magnetoencephalography to record the brain activity of 10 male and 10 female participants while they decided whether or not they considered examples of artistic and natural visual stimuli to be beautiful. Our results reveal significantly different activity between the sexes in parietal regions when participants judged the stimuli as beautiful. Activity in this region was bilateral in women, whereas it was lateralized to the right hemisphere in men. It is known that the dorsal visual processing stream, which encompasses the superior parietal areas, has been significantly modified throughout human evolution. We posit that the observed gender-related differences are the result of evolutionary processes that occurred after the splitting of the human and chimpanzee lineages. In view of previous results on gender differences with respect to the neural correlates of coordinate and categorical spatial strategies, we infer that the different strategies used by men and women in assessing aesthetic preference may reflect differences in the strategies associated with the division of labor between our male and female hunter-gatherer hominin ancestors.

They suggest:

...One possible explanation for the greater lateralization in men than in women could be grounded on differences between exploration strategies. Women would carry out an exploration of categorical spatial relations. The processes occurring in the right hemisphere of male participants suggest an exploration strategy based on coordinate spatial relations.
...there are other alternatives to the interpretation based on spatial exploration strategies. It is generally accepted that the right parietal cortex is associated with global visual attention and the left with local attention. Perhaps women make use of both global and local features in making their judgments, whereas men only rely on global features.
...Another hypothesis could link the observations to language. Women obtain higher scores on a diversity of verbal and language tasks. Perhaps women are more likely to associate the images with verbal labels than men, producing the lateralizing differences in neural activity.

They feel that:

...hunter-gatherer hypothesis of gender differences in spatial abilities provides the most convincing scenario. Differences in spatial ability between men and women would be associated with the division of labor between the sexes in hunting and gathering.

A map of knowledge

When we click from one page to another while looking through online scientific journals, we generate a chain of connections between things we think belong together. Now a billion such 'clickstream events' have been analyzed to map these connections on a grand scale. What emerges is a fascinating snapshot of the web of interconnections between disciplines, which some data-mining experts believe reveals the degree to which work that is not often cited — including work in the social sciences and humanities — is widely consulted and can form bridges between scientific disciplines. The authors of the maps argue that web-usage metrics give an alternative and more up-to-date view of science than existing maps and indicators, which are largely based on out-of-date citation data. (Try clicking on the map to enlarge it.)

How to lower your self control.

An interesting piece of work from Ackerman et al. We know that imagining or actively perceiving other people's actions can elicit many of the same neural and embodied responses that would occur if we performed those actions ourselves. This work shows that observing someone exerting self control sufficiently engages our empathetic mirroring of that process that it fatigues our own self control!

Acts of self-control may deplete an individual's self-regulatory resources. But what are the consequences of perceiving other people's use of self-control? Mentally simulating the actions of others has been found to elicit psychological effects consistent with the actual performance of those actions. Here, we consider how simulating versus merely perceiving the use of willpower can affect self-control abilities. In a first study, participants who simulated the perspective of a person exercising self-control exhibited less restraint over spending on consumer products than did other participants. In a second study, participants who took the perspective of a person using self-control exerted less willpower on an unrelated lexical generation task than did participants who took the perspective of a person who did not use self-control. Conversely, participants who merely read about another person's self-control exerted more willpower than did those who read about actions not requiring self-control. These findings suggest that the actions of other people may either deplete or boost one's own self-control, depending on whether one mentally simulates those actions or merely perceives them.

Gay scientists isolate christian gene.

My thanks to Mark Weber for bringing this satire to my attention.

Gesturing enhances learning in children

Goldin-Meadow and collaborators, whose work on the role of gesture in language development I have mentioned previously in two posts, now demonstrate that gesturing helps children learn math:

How does gesturing help children learn? Gesturing might encourage children to extract meaning implicit in their hand movements. If so, children should be sensitive to the particular movements they produce and learn accordingly. Alternatively, all that may matter is that children move their hands. If so, they should learn regardless of which movements they produce. To investigate these alternatives, we manipulated gesturing during a math lesson. We found that children required to produce correct gestures learned more than children required to produce partially correct gestures, who learned more than children required to produce no gestures. This effect was mediated by whether children took information conveyed solely in their gestures and added it to their speech. The findings suggest that body movements are involved not only in processing old ideas, but also in creating new ones. We may be able to lay foundations for new knowledge simply by telling learners how to move their hands.

Rehab, neuroscience, and religion

Jim Schnabel offers a brief essay in NatureNews on neuroscientists who are suggesting that is effectiveness of drug intervention programs is related to their strengthening of executive frontal lobe functions. Here are a few clips:

The modern addiction rehabilitation industry...even today is dominated by Wilson's Alcoholics Anonymous (AA) paradigm and its 'twelve-step' approach to recovery. Perhaps unsurprisingly, given its spiritual origins, this approach has had an uneasy relationship with the evidence-based culture of medical research. Both perceive addiction as a chronic disease; but whereas scientists seek rationally targeted interventions to blunt drug cravings, AA and related programmes tend to feature group therapy, tearful confessions and the call to "surrender to a higher power"...In the past few years, however, these two cultures have been finding common ground. Neuroscientists have begun to recognize that some of the most important brain systems impaired in addiction are those in the prefrontal cortex that regulate social cognition, self-monitoring, moral behaviour and other processes that the AA-type approach seems to target....treatment programmes are targeting these systems without necessarily knowing that they are doing it.

Religion has been shown to have a strong inverse association with drug addiction...Michael McCullough, who studies religion and behaviour at the University of Miami in Florida, suggests that when a person commits to any cultural system that regulates behaviour, the psychological effort to conform strengthens the brain systems that mediate self-monitoring and self-control. "What makes religion unique, I think, is that the code of conduct isn't just laid down by your parents or your friends or your principal at school, but ostensibly by the individual who is superintending the Universe, so it has an extra moral force." Some religious rituals, he says, have been shown to provoke enhanced activity in prefrontal regions (see Azari et al.). "It's as if certain forms of prayer and meditation are pinpointing precisely those [prefrontal] areas of the brain that people rely on to control attention, to control negative emotion and resolve mental conflict."

In pursuing other ways to boost prefrontal systems medicines for ADHD seem an obvious place to start. Attention-enhancing drugs such as methyl-phenidate and atomoxetine boost the activity of key receptor systems in the prefrontal cortex, in particular those for noradrenaline and dopamine. ..The National Institute on Drug Abuse has also been supporting studies of cognitive and behavioural strategies, and Volkow says that she is particularly enthusiastic about an approach that involves "real-time fMRI feedback". Developed by researcher and entrepreneur Christopher deCharms earlier this decade, the technique involves placing drug users in an fMRI machine and showing them a symbolic representation — a flame — of the fMRI-measured brain activity that corresponds to their cravings. The users are then asked to apply their own cognitive exercises, such as imagining their child is with them, to quench their cravings and douse the flame. After half a dozen sessions with this feedback the user will, in principle, develop cognitive circuitry that is more efficient at suppressing craving and that can then be used in ordinary life. A version of the technique, used for pain relief, has already shown some efficacy in a small clinical trial, and deCharms and his Silicon Valley start-up, Omneuron, are currently running a small trial in smokers — with plans for a follow up with some of Childress's cocaine users.

Negative attitude towards aging when young: decrease in later cardiovascular health.

Levy et al. examine a cohort of 440 individuals drawn from the Baltimore Longitudinal Study of Aging whose attitudes on aging was tested starting in 1968 when they were young (18–49 years, mean age = 36.5 years) and then noted cardiovascular events (89 total, including angina attacks, congestive heart failures, myocardial infarctions, strokes, and transient ischemic attacks) until 2007. 30 years after participants had responded to the age stereotype measure 25% of those with negative-age-stereotypes had experienced a cardiovascular event, compared to 13% who had positive-age-stereotypes.


Association between age stereotypes and time until experiencing a first cardiovascular (CV) event. The graph shows the percentage of participants who had not experienced a CV event as a function of time in each age-stereotype group.

Mental fatigue impairs our physical performance.

This study by Marcora et al. compared subjects who first either watched a movie for 90 min., or did computer exercises requiring concentration, memory and reaction speed - following which all exercised on a stationary bicycle until they were exhausted — that is, unable to maintain a cadence of 60 revolutions per minute. There were no significant differences in physiological measures (heart rate, cardiac output and others) under the two conditions, but bicyclers consistently tired about 15 percent more quickly after the mental exercise than after watching the movies. Apparently their poorer exercise results after mental effort were not caused by reduced performance of their bodies, but because mental fatigue limits exercise tolerance through higher perception of effort.

The Ricky Gervais Show on the "I-Illusion"

Thanks to my son Jon for pointing me to this humorous video.

Neural correlates of religious belief - neuroscience and spirituality

I'm realizing that I have a sufficient number of notes from this area in my queue that I'm not going to get to them separately. So, here I pass on first some links to recent publications and then some work on neural correlates of religious belief.

First, three publications:

"How God changes your brain"

"Contemplative Science: Where Buddhism and Neuroscience Converge"

A conference on Neuroscience and spiritual practices

Next,
Kapogiannis and collaborators attempt to model the complexity of religious belief and then provide brain imaging data correlate their categories with well known brain networks:

We propose an integrative cognitive neuroscience framework for understanding the cognitive and neural foundations of religious belief. Our analysis reveals 3 principle psychological dimensions of religious belief (God's perceived level of involvement, God's perceived emotion, and doctrinal/experiential religious knowledge), which functional MRI localizes within networks processing Theory of Mind regarding intent and emotion, abstract semantics, and imagery. Our results are unique in demonstrating that specific components of religious belief are mediated by well-known brain networks, and support contemporary psychological theories that ground religious belief within evolutionary adaptive cognitive functions.

In a less ambitious effort, Inzlicht et al. suggest that religious people are more chilled out when they commit errors, reflected by reduced reactivity of their anterior cingulate cortex:

Many people derive peace of mind and purpose in life from their belief in God. For others, however, religion provides unsatisfying answers. Are there brain differences between believers and nonbelievers? Here we show that religious conviction is marked by reduced reactivity in the anterior cingulate cortex (ACC), a cortical system that is involved in the experience of anxiety and is important for self-regulation. In two studies, we recorded electroencephalographic neural reactivity in the ACC as participants completed a Stroop task. Results showed that stronger religious zeal and greater belief in God were associated with less firing of the ACC in response to error and with commission of fewer errors. These correlations remained strong even after we controlled for personality and cognitive ability. These results suggest that religious conviction provides a framework for understanding and acting within one's environment, thereby acting as a buffer against anxiety and minimizing the experience of error.

To be less helpful to others, watch violent media...

A sobering study from Bushman and Anderson:

Two studies tested the hypothesis that exposure to violent media reduces aid offered to people in pain. In the first study, participants played a violent or nonviolent video game for 20 min. After game play, while completing a lengthy questionnaire, they heard a loud fight, in which one person was injured, outside the lab. Participants who played violent games took longer to help the injured victim, rated the fight as less serious, and were less likely to "hear" the fight in comparison to participants who played nonviolent games. In the second study, violent- and nonviolent-movie attendees witnessed a young woman with an injured ankle struggle to pick up her crutches outside the theater either before or after the movie. Participants who had just watched a violent movie took longer to help than participants in the other three conditions. The findings from both studies suggest that violent media make people numb to the pain and suffering of others.

How to enhance the wisdom of one...

The point of James Surowiecki's engaging book, "The Wisdom of Crowds" is that a marketplace - of ideas, goods, services, whatever - can make astonishingly accurate predictions of election outcomes, Oscar winners, etc. Herzog and Hertwig ask how a single individual might improve a best guess for an outcome and test a Hegelian process they call "dialectical bootstrapping." After making the first estimate, consider the reasons and assumptions underpinning that estimate (and how they might be off target), and then formulate a new, second estimate that harks back to somewhat different knowledge.

They tested the efficacy of this method by asking 101 students at the University of Basel to date a collection of 40 historical events (e.g., the discovery of electricity), 10 each from the 16th, 17th, 18th, and 19th centuries. Each participant was randomly assigned to one of two conditions. In both conditions, participants first generated their estimates without knowing that they would be asked later to generate a second estimate. In the dialectical-bootstrapping condition, participants (n= 50) were then asked to give dialectical estimates (while their first estimates were displayed in front of them) using a technique inspired by the consider-the-opposite strategy: First, assume that your first estimate is off the mark. Second, think about a few reasons why that could be. Which assumptions and considerations could have been wrong? Third, what do these new considerations imply? Was the first estimate rather too high or too low? Fourth, based on this new perspective, make a second, alternative estimate.

They found that the improvement in accuracy (in years) over the first estimate was twice as large for the dialectical average than for the repeat average, although averaging the first estimates from two random individuals worked better still.

Roots of our social glue

Angier does a nice summary of ideas in Hrdy's forthcoming new book “Mothers and Others: The Evolutionary Origins of Mutual Understanding,” (Harvard Univ. Press):

...the extraordinary social skills of an infant are at the heart of what makes us human. Through its ability to solicit and secure the attentive care not just of its mother but of many others in its sensory purview, a baby promotes many of the behaviors and emotions that we prize in ourselves and that often distinguish us from other animals, including a willingness to share, to cooperate with strangers, to relax one’s guard...Our capacity to cooperate in groups, to empathize with others and to wonder what others are thinking and feeling...probably arose in response to the selective pressures of being in a cooperatively breeding social group, and the need to trust and rely on others and be deemed trustworthy and reliable in turn. Babies became adorable and keen to make connections with every passing adult gaze....mother chimpanzees and gorillas jealously hold on to their infants for the first six months or more of life. Other females may express real interest in the newborn, but the mother does not let go: you never know when one of those females will turn infanticidal, or be unwilling or unable to defend the young ape against an infanticidal male.

Dr. Hrdy wrote her book in part to counter what she sees as the reigning dogma among evolutionary scholars that humans evolved their extreme sociality and cooperative behavior to better compete with other humans. “I’m not comfortable accepting this idea that the origins of hypersociality can be found in warfare, or that in-group amity arose in the interest of out-group enmity,” she said in a telephone interview. Sure, humans have been notably violent and militaristic for the last 12,000 or so years, she said, when hunter-gatherers started settling down and defending territories, and populations started getting seriously dense. But before then? There weren’t enough people around to wage wars. By the latest estimates, the average population size during the hundreds of thousands of years of human evolution that preceded the Neolithic Age may have been around 2,000 breeding adults. “What would humans have been fighting over?” Dr. Hrdy said. “They were too busy trying to keep themselves and their children alive.”

Dr. Hrdy also argues that our human ancestors became emotionally modern long before the human brain had reached its current average volume of 1,300 cubic centimeters, which is about three times the size of a chimpanzee brain — in other words, that we became the nicest apes before becoming the smartest. You don’t need a bulging brain to evolve cooperative breeding. Many species of birds breed cooperatively, as do lions, rats, meerkats, wolves and marmosets, among others. But to become a cooperatively breeding ape, and to persuade a bunch of smart, hot-tempered, suspicious, politically cunning primates to start sharing child care and provisionings, now that took a novel evolutionary development, the advent of this thing called trust.