"Us" versus "Them" in 17 month old infants.

Jin and Baillargeon make observations that suggest an early origin of the 'us and them' perspective being taken to extremes in our current polarized political climate:

Significance

We examined whether one mechanism contributing to ingroup favoritism might be an abstract and early-emerging sociomoral expectation of ingroup support. In violation-of-expectation experiments, 17-mo-old infants first watched third-party interactions among unfamiliar adults identified (using novel labels) as belonging to the same group, to different groups, or to unspecified groups. Next, one adult needed help, and another adult either did or did not provide it. Infants expected help to be provided when the two adults belonged to the same group, but held no expectation when the adults belonged to different groups or to unspecified groups. Infants thus already possess an abstract expectation of ingroup support, and this finding sheds light on one of the mechanisms underlying ingroup favoritism in human interactions.

Abstract

One pervasive facet of human interactions is the tendency to favor ingroups over outgroups. Remarkably, this tendency has been observed even when individuals are assigned to minimal groups based on arbitrary markers. Why is mere categorization into a minimal group sufficient to elicit some degree of ingroup favoritism? We consider several accounts that have been proposed in answer to this question and then test one particular account, which holds that ingroup favoritism reflects in part an abstract and early-emerging sociomoral expectation of ingroup support. In violation-of-expectation experiments with 17-mo-old infants, unfamiliar women were first identified (using novel labels) as belonging to the same group, to different groups, or to unspecified groups. Next, one woman needed instrumental assistance to achieve her goal, and another woman either provided the necessary assistance (help event) or chose not to do so (ignore event). When the two women belonged to the same group, infants looked significantly longer if shown the ignore as opposed to the help event; when the two women belonged to different groups or to unspecified groups, however, infants looked equally at the two events. Together, these results indicate that infants view helping as expected among individuals from the same group, but as optional otherwise. As such, the results demonstrate that from an early age, an abstract expectation of ingroup support contributes to ingroup favoritism in human interactions.

Cognitive control increases honesty in cheaters but cheating in those who are honest

Abe discusses work of Speer et al. that probes:

..a long-standing paradox concerning the cognitive nature of honesty: Is it a matter of “will” or “grace”? The will hypothesis assumes that honesty requires cognitive control to suppress temptation to cheat, while dishonest behavior to serve self-interest is people’s automatic response. In contrast, the grace hypothesis assumes that honesty flows automatically without active resistance to temptation, while dishonest behavior is realized by cognitive control to override honest impulses.

Here is the Speer et al. abstract:

Every day, we are faced with the conflict between the temptation to cheat for financial gains and maintaining a positive image of ourselves as being a “good person.” While it has been proposed that cognitive control is needed to mediate this conflict between reward and our moral self-image, the exact role of cognitive control in (dis)honesty remains elusive. Here we identify this role, by investigating the neural mechanism underlying cheating. We developed a task which allows for inconspicuously measuring spontaneous cheating on a trial-by-trial basis in the MRI scanner. We found that activity in the nucleus accumbens promotes cheating, particularly for individuals who cheat a lot, while a network consisting of posterior cingulate cortex, temporoparietal junction, and medial prefrontal cortex promotes honesty, particularly in individuals who are generally honest. Finally, activity in areas associated with cognitive control (anterior cingulate cortex and inferior frontal gyrus) helped dishonest participants to be honest, whereas it enabled cheating for honest participants. Thus, our results suggest that cognitive control is not needed to be honest or dishonest per se but that it depends on an individual’s moral default.

Origins of human music - two perspectives

Because I wrote an article in Behavioral and Brain Sciences (coauthored with Vadim Arshavsky), that was published in 2010, I receive the journal's calls for commentaries on forthcoming articles. Here I pass on the abstracts of two articles proposing evolutionary rationales for the origins of our human musical abilities.  Because I am a recital pianist I have always been interested in the origins and neuroscience of our musical faculties. In 2015 I agreed to give a lecture on 'Music and the Mind', generated thirty pages of fairly lucid text, became overwhelmed by the complexity of the subject, and backed out of doing the talk.  I'm curious to see whether a careful reading of these articles confirms that decision or inspires me to try again. 

Music as a coevolved system for social bonding

Why do humans make music? Theories of the evolution of musicality have focused mainly on the value of music for specific adaptive contexts such as mate selection, parental care, coalition signaling, and group cohesion. Synthesizing and extending previous proposals, we argue that social bonding is an overarching function that unifies all of these theories, and that musicality enabled social bonding at larger scales than grooming and other bonding mechanisms available in ancestral primate societies. We combine cross-disciplinary evidence from archaeology, anthropology, biology, musicology, psychology, and neuroscience into a unified framework that accounts for the biological and cultural evolution of music. We argue that the evolution of musicality involves gene-culture coevolution, through which proto-musical behaviors that initially arose and spread as cultural inventions had feedback effects on biological evolution due to their impact on social bonding. We emphasize the deep links between production, perception, prediction, and social reward arising from repetition, synchronization, and harmonization of rhythms and pitches, and summarize empirical evidence for these links at the levels of brain networks, physiological mechanisms, and behaviors across cultures and across species. Finally, we address potential criticisms and make testable predictions for future research, including neurobiological bases of musicality and relationships between human music, language, animal song, and other domains. The music and social bonding (MSB) hypothesis provides the most comprehensive theory to date of the biological and cultural evolution of music.

Origins of music in credible signaling

Music comprises a diverse category of cognitive phenomena that likely represent both the effects of psychological adaptations that are specific to music (e.g., rhythmic entrainment) and the effects of adaptations for non-musical functions (e.g., auditory scene analysis). How did music evolve? Here, we show that prevailing views on the evolution of music — that music is a byproduct of other evolved faculties, evolved for social bonding, or evolved to signal mate quality — are incomplete or wrong. We argue instead that music evolved as a credible signal in at least two contexts: coalitional interactions and infant care. Specifically, we propose that (1) the production and reception of coordinated, entrained rhythmic displays is a co-evolved system for credibly signaling coalition strength, size, and coordination ability; and (2) the production and reception of infant-directed song is a co-evolved system for credibly signaling parental attention to secondarily altricial infants. These proposals, supported by interdisciplinary evidence, suggest that basic features of music, such as melody and rhythm, result from adaptations in the proper domain of human music. The adaptations provide a foundation for the cultural evolution of music in its actual domain, yielding the diversity of musical forms and musical behaviors found worldwide.

The science of inequality.

Economic inequality is a continuing focus of political debate, and I think a re-post of a brief MindBlog item from 6/2/2014 is relevant:

The May 23 issue of Science Magazine has a large section devoted the origins and analysis of economic inequality. And, the general gist of virtually all the articles is that inequality is here to stay, predicted by social and also simple physical models of exchange. A weekly chaos and complexity discussion group that I attend just this past Tuesday discussed the economic Yard-Sale Model of wealth redistribution, in which power-law-like distributions result even when all individuals are identical and playing by the same rules. In a previous post, I have passed on a simple model illustrated by Clint Sprott, organizer of the seminars.

Predicting results of our presidential election.

I want to pass on an email from retired historian Lou Wangberg, a friend from my Fort Lauderdale period who leads a history discussion group there. He gives links to analyses by The Economist magazine and Mind Matters A.I.

Between now and the election on November 3rd you will see literally countless polls and forecasts. You see, as humans we hate to live with uncertainty. We want to know in advance what is ahead for us. And it is a legitimate question to ask, "Which poll(s) should I pay attention to? "Which poll(s) will be most on target?" the answer is NONE OF THEM. In the end virtually all of them will be wrong for one reason or another. That is why we hold elections. But I have found one that is more sophisticated than the rest and uses 20,000 factors. It also goes day by day so it is interesting to watch. So give this one a try and you will at least have something you can quote in your discussions (arguments) with friends. I'm going to share an additional link that will explain why most predictions are bogus. Enjoy! Here are the links:

The Economist - Forecasting the US elections

Mind Matters - Election Models: Predicting the past is easy - and useless

Democracy in the Balance - Special Issue of Science Magazine

The Sept.4 issue of Science Magazine has a special section of open source perspectives and reviews. A few of the titles:

Racial authoritarianism in U.S. democracy

Campaigns influence election outcomes less than you think

Diversity and prosocial behavior

False equivalencies: Online activism from left to right

The illusion of objectivity enhances political polarization.

From Schwalbe et al. (open source):  

Significance

Political polarization increasingly threatens democratic institutions. The belief that “my side” sees the world objectively while the “other side” sees it through the lens of its biases contributes to this political polarization and accompanying animus and distrust. This conviction, known as the “objectivity illusion,” was strong and persistent among Trump and Clinton supporters in the weeks before the 2016 presidential election. We show that the objectivity illusion predicts subsequent bias and polarization, including heightened partisanship over the presidential debates. A follow-up study showed that both groups impugned the objectivity of a putative blog author supporting the opposition candidate and saw supporters of that opposing candidate as evil.

Abstract

Two studies conducted during the 2016 presidential campaign examined the dynamics of the objectivity illusion, the belief that the views of “my side” are objective while the views of the opposing side are the product of bias. In the first, a three-stage longitudinal study spanning the presidential debates, supporters of the two candidates exhibited a large and generally symmetrical tendency to rate supporters of the candidate they personally favored as more influenced by appropriate (i.e., “normative”) considerations, and less influenced by various sources of bias than supporters of the opposing candidate. This study broke new ground by demonstrating that the degree to which partisans displayed the objectivity illusion predicted subsequent bias in their perception of debate performance and polarization in their political attitudes over time, as well as closed-mindedness and antipathy toward political adversaries. These associations, furthermore, remained significant even after controlling for baseline levels of partisanship. A second study conducted 2 d before the election showed similar perceptions of objectivity versus bias in ratings of blog authors favoring the candidate participants personally supported or opposed. These ratings were again associated with polarization and, additionally, with the willingness to characterize supporters of the opposing candidate as evil and likely to commit acts of terrorism. At a time of particular political division and distrust in America, these findings point to the exacerbating role played by the illusion of objectivity.

Mechanisms of our current political polarization.

I want to point to three sources that provide complimentary perspectives on the origins and maintenance of the extreme Red versus Blue divide in the U.S.:

The first is a freakonomics podcast, with a text version also offered,  describing how Republicans and Democrats form a duopoly analogous to Coke and Pepsi, Intel and AMD, Boeing and Airbus, etc.

"America's Hidden Duopoly - We all know our political system is “broken” — but what if that’s not true? Some say the Republicans and Democrats constitute a wildly successful industry that has colluded to kill off competition, stifle reform, and drive the country apart.  So, what can we do about it?

A second perspective is offered by Yang et al., who provide a "Satisficing" Dynamical Model of why U.S. political parties are so polarized. Here is a summary by Clint Sprott of the Univ. of Wisc. Chaos and Complex Systems Discussion Group:

Basically, it contends that when the parties are too centrist and too inclusive, voters with extreme views find little reason to choose one over the other and either abstain from voting or vote randomly. Thus it is advantageous for the parties to move off center to pick up more of these voters. In the coming election, most people long ago decided which side they are on. Thus all the parties can hope to do at this point is to induce those who lean in their direction to get out and vote. Would mandatory voting reduce polarization? Why is the popular vote usually so close to 50/50?

And finally, a book by Achen and Bartels, "Democracy for Realists: Why Elections Do Not Produce Responsive Government." From the book description:

Democracy for Realists assails the romantic folk-theory at the heart of contemporary thinking about democratic politics and government, and offers a provocative alternative view grounded in the actual human nature of democratic citizens.

Christopher Achen and Larry Bartels deploy a wealth of social-scientific evidence, including ingenious original analyses of topics ranging from abortion politics and budget deficits to the Great Depression and shark attacks, to show that the familiar ideal of thoughtful citizens steering the ship of state from the voting booth is fundamentally misguided. They demonstrate that voters―even those who are well informed and politically engaged―mostly choose parties and candidates on the basis of social identities and partisan loyalties, not political issues. They also show that voters adjust their policy views and even their perceptions of basic matters of fact to match those loyalties. When parties are roughly evenly matched, elections often turn on irrelevant or misleading considerations such as economic spurts or downturns beyond the incumbents' control; the outcomes are essentially random. Thus, voters do not control the course of public policy, even indirectly.

The active grandparent hypothesis - an evolutionary explanation of why and how exercise delays senescence and death.

I recommend that you read an interesting article by Daniel Lieberman in the current issue of Harvard Magazine. Here are a few clips:

The evidence that hunter-gatherers stay physically active for several decades after they stop having children is fundamental for understanding the nature of human aging. Most especially, our uniquely cooperative system of intergenerational cooperation and food-sharing postpones Medawar’s grim shadow. Instead of becoming obsolete, middle-aged and elderly hunter-gatherers bolster their reproductive success by provisioning children and grandchildren, doing childcare, processing food, passing on expertise, and otherwise helping younger generations. Once this novel cooperative strategy—the essence of the hunting and gathering way of life—started to emerge during the Stone Age, natural selection had the chance to select for longevity. According to this theory, hard-working and helpful grandparents who looked out for others and who were blessed with genes that favored a long life had more children and grandchildren, thus passing on those genes. Over time, humans were evidently selected to live longer to be generous, useful grandparents. One version of this idea is known as the Grandmother Hypothesis in recognition of the evidence that grandmothers play especially important roles.

In order to elucidate the links between exercise and aging, I propose a corollary to the Grandmother Hypothesis, which I call the Active Grandparent Hypothesis. According to this idea, human longevity was not only selected for but was also made possible by having to work hard during old age to help as many children, grandchildren, and other younger relatives as possible survive and thrive. That is, while there may have been selection for genes (as yet unidentified) that help humans live past the age of 50, there was also selection for genes that repair and maintain our bodies when we are physically active. As a result, many of the mechanisms that slow aging and extend life are turned on by physical activity, especially as we get older. Human health and longevity are thus extended both by and for physical activity.

While exercise restores most structures (what biologists term homeostasis), in some cases it may create stability by making things even better than before (allostasis). For example, demanding physical activities can increase the strength of bones and muscles, increase cells’ abilities to uptake glucose from the blood, and both augment and replace mitochondria in muscles. In addition, repair mechanisms sometimes overshoot the damage induced by exercise, leading to a net benefit. It’s like scrubbing the kitchen floor so well after a spill that the whole floor ends up being cleaner. All in all, the modest physiological stresses caused by exercise trigger a reparative response yielding a general benefit, a phenomenon sometimes known as hormesis.

Changes as MindBlog's autonomic nervous system ages 11 years

Actually, the original title of this MindBlog post on June 11, 2013 was "Changes as an autonomic nervous system ages 11 years - The "Wild Divine" is a bit less wild." - I'm reviewing old MindBlog posts (very slowly, as it turns out) and in most cases resisting the temptation to re-post even ones I thinks are quite interesting. This personal one really hit me, owever, so I pass it on, wondering how much further the noted decrease in my ability to regulate autonomic nervous system parameters has progressed by age 78:

Just after I retired from being a Univ. of Wisconsin department chair in 2001 I bought a set of finger sensors that fit on one's three middle fingers to report skin conductance and heartbeat to a PC or MAC via an A/D converter. These were part of a package with several CDs that installed a new age game on the computer that lead you through a rich environment of classical greek temples and waterfalls, attended by soothing music, that presented tasks in which you dinked with your own heart rate variability and sympathetic (arousing)/parasympathetic (calming) balance, going alternatively through periods of calm and arousal. I thought it was a hoot, and took the time to go through the "Journey to Wild Divine: passage" and "Journey to Wild Divine: Wisdom Quest."

Some of the current incarnations of these programs have moved to web browsers. Over the years a number of heavy weight new age gurus have signed on with their wares - Deepak Chopra, Dean Ornish, and Andrew Weil (Weil was in my Harvard graduating class...I'm tempted, but I won't burden you with my jaded opinion of this class of entrepreneurs, particularly Mr. Chopra.)

The main point of this post is note my experience on pulling out the finger sensors after 11 years trying the same exercises in their new presentation. What's the difference when this 71 year old tries the same manipulations of calm and arousal that the 60 year old played with with 11 years earlier? In a nutshell, I have less command over heart rate variability, which is lower, as the swings between calm and arousal have less amplitude.

And indeed, this fits with the literature on changes in the autonomic nervous system that occur on aging. If you simply do a google search for "autonomic nervous system and aging" numerous references appear that document how healthy aging is associated with lowered heart rate variability, elevated basal sympathetic nervous activity, and reduction of overall autonomic reactivity of sympathetic and parasympathetic nervous systems. Here is a very recent review, from which I pass on one figure:

Schematic of proposed features associated with the imbalance in the autonomic nervous system during aging. During aging there is a shift in the balance of the autonomic nervous system (ANS) towards the sympathetic nervous system (SNS). This may be influenced by circulating or local brain levels of angiotensin (Ang) II and leptin. The lower activity of the parasympathetic nervous system (PSNS) is proposed to result at least in part from an age-related decline in Angiotensin-(1–7). Lower Angiotensin-(1–7) and higher Ang II or leptin in the brain medulla would predispose to a decline in baroreceptor reflex sensitivity (BRS) for control of heart rate and heart rate variability (HRV), both of which are associated with aging. Moreover, impairments in BRS and HRV can contribute to target organ damage, including metabolic dysfunction, with or without an increase in blood pressure. 

If you're inclined, like Mr. Dylan Thomas, to not "go gently into that good night" you can find numerous sources (example here) on slowing these aging changes, usually by some sort of physical movement or stimulation.

Reconsidering the value of believing in free will.

Nadelhoffer et al. fail to replicate 2008 experiments suggesting that a belief in determinism increases cheating:

A key source of support for the view that challenging people's beliefs about free will may undermine moral behavior is two classic studies by Vohs and Schooler (2008). These authors reported that exposure to certain prompts suggesting that free will is an illusion increased cheating behavior. In the present paper, we report several attempts to replicate this influential and widely cited work. Over a series of five studies (sample sizes of N = 162, N = 283, N = 268, N = 804, N = 982) (four preregistered) we tested the relationship between (1) anti-free-will prompts and free will beliefs and (2) free will beliefs and immoral behavior. Our primary task was to closely replicate the findings from Vohs and Schooler (2008) using the same or highly similar manipulations and measurements as the ones used in their original studies. Our efforts were largely unsuccessful. We suggest that manipulating free will beliefs in a robust way is more difficult than has been implied by prior work, and that the proposed link with immoral behavior may not be as consistent as previous work suggests.

A brief history of risk

Li, Hills, and Hertwig do an open access review with the title of this post. From their introductory paragraph:

...First, we examined how the frequency of the word risk has changed over historical time. Is the construct of risk playing an ever-increasing role in the public discourse, as the sociological notion of a ‘risk society’ suggests? Second, we investigated how the sentiments for the words co-occurring with risk have changed. Are the connotations of risk becoming increasingly ominous? Third, how has the meaning of risk changed relative to close associates such as danger and hazard? Is risk more subject to semantic change? Finally, we decompose the construct of risk into the specific topics with which it has been associated and track those topics over historical time. This brief history of the semantics of risk reveals new and surprising insights—a fourfold increase in frequency, increasingly negative sentiment, a semantic drift toward forecasting and prevention, and a shift away from war toward chronic disease—reflecting the conceptual evolution of risk in the archeological records of public discourse.

Getting the rhythm to suppress Alzheimer's

An interesting brief open source review by Lynne Peeples in PNAS describes experiments on mice and humans showing that visual and sound stimulation in the e.e.g gamma frequency range (30-80 Hertz, or cycles/sec, peaking at 40 Hz) elicits gamma frequency brain oscillation, enhance cognition, and diminishes levels of the amyloid plaques and tau protein tangles associated with Alzheismer's. The article is worth a read, and I pass on just a bit of a background paragraph:

Brain rhythms are known to participate in all forms of cognition. And changes of brain rhythms appear to be implicated in all forms of neurological disease...Growing evidence indicates that neurons in many animals, including humans, can strongly synchronize in the gamma range of frequencies—between 30 and 80 hertz, and peaking around 40 hertz. As far back as a 1955 study of meditating yogis, researchers have associated gamma waves with peak concentration and high levels of cognitive functioning. Studies in the last decade that manipulated brain rhythms in lab animals and humans have confirmed the impact of those rhythms on cognition and disease. Researchers have also found that fewer neurons fire together at this rate in patients with Alzheimer’s disease or other neurological conditions, suggesting that gamma rhythms may play a role in the cognitive impairments associated with such disorders.

Rice-farming predicts tigher social norms, less innovative thinking, worldwide

From Talhelm and English (open source):

Data recently published in PNAS mapped out regional differences in the tightness of social norms across China [R. Y. J. Chua, K. G. Huang, M. Jin, Proc. Natl. Acad. Sci. U.S.A. 116, 6720–6725 (2019)]. Norms were tighter in developed, urbanized areas and weaker in rural areas. We tested whether historical paddy rice farming has left a legacy on social norms in modern China. Premodern rice farming could plausibly create strong social norms because paddy rice relied on irrigation networks. Rice farmers coordinated their water use and kept track of each person’s labor contributions. Rice villages also established strong norms of reciprocity to cope with labor demands that were twice as high as dryland crops like wheat. In line with this theory, China’s historically rice-farming areas had tighter social norms than wheat-farming areas, even beyond differences in development and urbanization. Rice–wheat differences were just as large among people in 10 neighboring provinces (n = 3,835) along the rice–wheat border. These neighboring provinces differ sharply in rice and wheat, but little in latitude, temperature, and other potential confounding variables. Outside of China, rice farming predicted norm tightness in 32 countries around the world. Finally, people in rice-farming areas scored lower on innovative thinking, which tends to be lower in societies with tight norms. This natural test case within China might explain why East Asia—historically reliant on rice farming—has tighter social norms than the wheat-farming West.

Stable isotopes in hair reveal dietary divergence related to socioeconomic status and health

From Ehleringer et al.:

Carbon and nitrogen isotope ratios in hair sampled from 65 communities across the central and intermountain regions of the United States and more intensively throughout 29 ZIP codes in the Salt Lake Valley, Utah, revealed a dietary divergence related to socioeconomic status as measured by cost of living, household income, and adjusted gross income. Corn-fed, animal-derived proteins were more common in the diets of lower socioeconomic status populations than were plant-derived proteins, with individual estimates of animal-derived protein diets as high as 75%; United States towns and cities averaged 57%. Similar patterns were seen across the socioeconomic status spectrum in the Salt Lake Valley. It is likely that corn-fed animal proteins were associated with concentrated animal-feeding operations, a common practice for industrial animal production in the United States today. Given recent studies highlighting the negative impacts of animal-derived proteins in our diets, hair carbon isotope ratios could provide an approach for scaling assessments of animal-sourced foods and health risks in communities across the United States.

Gaze deflection reveals how gaze cueing is tuned to extract the mind behind the eyes

Here is a fascinating bit from Colombatto et al.:  

Significance

We report an empirical study of gaze deflection—a common experience in which you turn to look in a different direction when someone “catches” you staring at them. We show that gaze cueing (the automatic orienting of attention to locations at which others are looking) is far weaker for such displays, even when the actual eye and head movements are identical to more typical intentional gazes. This demonstrates how gaze cueing is driven by the perception of minds, not eyes, and it serves as a case study of both how social dynamics can shape visual attention in a sophisticated manner and how vision science can contribute to our understanding of common social phenomena.

Abstract

Suppose you are surreptitiously looking at someone, and then when they catch you staring at them, you immediately turn away. This is a social phenomenon that almost everyone experiences occasionally. In such experiences—which we will call gaze deflection—the “deflected” gaze is not directed at anything in particular but simply away from the other person. As such, this is a rare instance where we may turn to look in a direction without intending to look there specifically. Here we show that gaze cues are markedly less effective at orienting an observer’s attention when they are seen as deflected in this way—even controlling for low-level visual properties. We conclude that gaze cueing is a sophisticated mental phenomenon: It is not merely driven by perceived eye or head motions but is rather well tuned to extract the “mind” behind the eyes.

Effects of lockdown on human sleep and chronotype during the COVID-19 pandemic

An open source article in Current Biology from Leone et al., the summary:

The COVID-19 pandemic resulted in many countries imposing a lockdown, which in turn reduces sunlight exposure and alters daily social schedules. Since these are the main entrainment factors for biological rhythms, we hypothesized that the lockdown may have affected sleep and circadian rhythms. We indeed show that participants slept longer and later during lockdown weekdays, and exhibited lower levels of social jetlag. While this may seem to be an overall improvement of sleep conditions, chronotype was also delayed under the lockdown. This signature of a weaker light–dark cycle should be monitored attentively since it may progressively cause disruptive effects on sleep and circadian rhythms, affecting human performance and health.

A model shows herd immunity to COVID can be achieved at a population-wide infection rate of ~40%

I pass on the editor's summary and the abstract for a open source article by Britton et al.:  

Heterogeneity and herd immunity

In response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), some politicians have been keen to exploit the idea of achieving herd immunity. Countering this possibility are estimates derived from work on historical vaccination studies, which suggest that herd immunity may only be achieved at an unacceptable cost of lives. Because human populations are far from homogeneous, Britton et al. show that by introducing age and activity heterogeneities into population models for SARS-CoV-2, herd immunity can be achieved at a population-wide infection rate of ∼40%, considerably lower than previous estimates. This shift is because transmission and immunity are concentrated among the most active members of a population, who are often younger and less vulnerable. If nonpharmaceutical interventions are very strict, no herd immunity is achieved, and infections will then resurge if they are eased too quickly.

Abstract

Despite various levels of preventive measures, in 2020, many countries have suffered severely from the coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Using a model, we show that population heterogeneity can affect disease-induced immunity considerably because the proportion of infected individuals in groups with the highest contact rates is greater than that in groups with low contact rates. We estimate that if R0 = 2.5 in an age-structured community with mixing rates fitted to social activity, then the disease-induced herd immunity level can be ~43%, which is substantially less than the classical herd immunity level of 60% obtained through homogeneous immunization of the population. Our estimates should be interpreted as an illustration of how population heterogeneity affects herd immunity rather than as an exact value or even a best estimate.

Philanthropy—or tax-exempt lobbying?

I pass on this piece by Brad Wible from the Editors' Choice section of the current issue of Science Magazine:

Major corporations appear to fund their charitable foundations in part to cater to politicians who are important to the firm's profitability. Integrating corporate tax returns, lobbying data, and data on U.S. congressional committee assignments, Bertrand et al. show that donations from a given corporate-funded foundation to charities in a particular congressional representative's district, or for which a congressional representative is a board member, ebb and flow according to whether the representative sits on a committee that is of interest to the corporation. The patterns parallel spending by political action committees (PACs). Around 7% of charitable giving (∼$1.2 billion annually) appears to be politically motivated, amounting to about 2.5 times the annual PAC spending and one-third of the total federal lobbying spending—and it is tax exempt and thus subsidized by taxpayers.

Am. Econ. Rev. 110, 2065 (2020).

Our default-mode network contains nine subnetworks serving different cognitive tasks.

Our brains are organized into large networks that can be identified during brain scanning. The default mode network, which has been the subject of many MindBlog posts (try the Blog's search function in the left column), engages a large number of inwardly directed cognitive functions such as mind-wandering, autobiographical and social thinking, memory, and reward. Gordon et al. now do resting-state functional connectivity studies distinguishing nine subnetworks with different specializations:

Significance

The human brain is organized into large networks. One important brain network is the Default network, which enables cognitive functions such as social thinking, memory, and reward. In group-averaged data, this network emerges as a unitary whole, despite its involvement in multiple cognitive functions. Here, we tested whether Default networks found in individual humans, rather than group-average networks, contain organized substructure. In individuals, we consistently found nine subnetworks within the Default network. These subnetworks matched brain activity patterns during cognitive tasks. Some subnetworks resembled brain circuits involved in specific Default functions. Others linked Default network to other large networks. In summary, this study describes a set of brain circuits within the Default networks of individual humans.

Abstract

The human brain is organized into large-scale networks identifiable using resting-state functional connectivity (RSFC). These functional networks correspond with broad cognitive domains; for example, the Default-mode network (DMN) is engaged during internally oriented cognition. However, functional networks may contain hierarchical substructures corresponding with more specific cognitive functions. Here, we used individual-specific precision RSFC to test whether network substructures could be identified in 10 healthy human brains. Across all subjects and networks, individualized network subdivisions were more valid—more internally homogeneous and better matching spatial patterns of task activation—than canonical networks. These measures of validity were maximized at a hierarchical scale that contained ∼83 subnetworks across the brain. At this scale, nine DMN subnetworks exhibited topographical similarity across subjects, suggesting that this approach identifies homologous neurobiological circuits across individuals. Some DMN subnetworks matched known features of brain organization corresponding with cognitive functions. Other subnetworks represented separate streams by which DMN couples with other canonical large-scale networks, including language and control networks. Together, this work provides a detailed organizational framework for studying the DMN in individual humans.