Metabolic and physical decline that occurs during aging promoted by a DNA repair enzyme.

Damage to our DNA accumulates during our aging, and Park et al. show a link between this damage and the loss of metabolic function associated with physical decline and aging-associated diseases. They show that DNA breaks activate the repair promoting enzyme DNA-dependent protein kinase (DNA-PK) in skeletal muscle, but the kinase also suppresses mitochondrial function, energy metabolism, and physical fitness. A small-molecule inhibitor of DNA-PK improves the physical fitness of young obese mice and older mice. Whether there is therapeutic potential in such small inhibitors depends on whether inhibition of DNA repair has deleterious effects, such as increasing the potential for cancer. Here is the abstract:

Hallmarks of aging that negatively impact health include weight gain and reduced physical fitness, which can increase insulin resistance and risk for many diseases, including type 2 diabetes. The underlying mechanism(s) for these phenomena is poorly understood. Here we report that aging increases DNA breaks and activates DNA-dependent protein kinase (DNA-PK) in skeletal muscle, which suppresses mitochondrial function, energy metabolism, and physical fitness. DNA-PK phosphorylates threonines 5 and 7 of HSP90α, decreasing its chaperone function for clients such as AMP-activated protein kinase (AMPK), which is critical for mitochondrial biogenesis and energy metabolism. Decreasing DNA-PK activity increases AMPK activity and prevents weight gain, decline of mitochondrial function, and decline of physical fitness in middle-aged mice and protects against type 2 diabetes. In conclusion, DNA-PK is one of the drivers of the metabolic and fitness decline during aging, and therefore DNA-PK inhibitors may have therapeutic potential in obesity and low exercise capacity.

A conclusion from one of my lectures.

While mulling over possible topics I might develop for a next lecture, I have looked back over previous efforts on dericbownds.net and found several bits of text that I like. I'm pasting in below the concluding paragraphs from my Lecture/Web Lecture "Upstairs/Downstairs in our Brain - What's running our show?"

I would submit that those mind therapies, meditations, or exercises that are the most effective in generating new more functional behaviors are those that come close to resolving what we could call the category error (in the spirit of the philosophical term) in considering mind and brain. And, that error is to confuse a product with its source, the source being the fundamental impersonal downstairs machinery that generates the varieties of functional or dysfunctional selves that are its product, that we mistakenly imagine ourselves to be. Mental exercises like meditation permit the intuition of, perhaps come closest to, that more refined metacognitive underlying generative space that permits viewing of, and choice between, more or less functional self options.

A less wordy, maybe more useful, way of putting this is to say that third person introspection, viewing yourself as if looking at another actor, and placing this a historical story line, is more useful than immersed rumination (coulda, shoulda, woulda). It is the difference between residing mainly in the attentional versus default modes of cognition.

If there is a practical take-home message, it is that maintaining awareness of, and exercising, focused upstairs frontal attentional mechanisms is important to mental vitality and longevity. Such awareness is central in resisting the attacks on our attentional competence that comes from the confusing media jungle that tempts our passive default mode receptivity and reactivity.

Some outstanding books on the biology of our behaviors.

If you are wanting to find a humorous, fascinating, engaging, authoritative account of why we humans behave the way we do, you should immediately buy a copy of Robert Sapolsky's new book, "Behave - The Biology of Humans at Our Best and Worst." I've been a fan of Sapolsky ever since reading his "Why Zebras don't get Ulcers," whose 3rd edition dates to 2004. His writing has a flexibility, lightness and sense of humor that I wish I could even begin to emulate. I'm only up to the third chapter (of 17), and wish I could suspend all my other activities and read this book. I'm familiar with virtually all of the material he presents, but I could never present it with his clarity and lucid organization.

Another book I want to make a positive comment about is Richard Haier's "The Neuroscience of Intelligence," part of the Cambridge Fundamentals of Neuroscience in Psychology series. It is a bit more academic and weighty, beginning by dispelling popular misinformation on intelligence and then describing how it is defined and measured for scientific research. The book reviews evidence for the importance of genetics and epigenetics, and has chapters that do a nice synthesis of neuroimaging and other new technologies. The final two chapters focus on approaches to enhancing intelligence, and also how intelligence research may inform education policies.

Finally, I want to mention a book by Ken Richardson, "Genes, Brains, and Human Potential," that discusses how the ideology of human intelligence has infiltrated genetics,  brain science, and psychology, so that (from the dust jacket) "ideology, more than pure science, has come to dominate our institutions, especially education, encouraging fatalism about the development of human intelligence among individuals and societies. Build on work being done in molecular biology, epigenetics, dynamical systems, evolution theory, and complexity theory, Richardson maps a fresh understanding of intelligence and the development of human potential informed by a more complete and nuanced understanding of both ideology and science."

Watching our brains construct linguistic phrases

From Nelson et al.:

Significance

According to most linguists, the syntactic structure of sentences involves a tree-like hierarchy of nested phrases, as in the sentence [happy linguists] [draw [a diagram]]. Here, we searched for the neural implementation of this hypothetical construct. Epileptic patients volunteered to perform a language task while implanted with intracranial electrodes for clinical purposes. While patients read sentences one word at a time, neural activation in left-hemisphere language areas increased with each successive word but decreased suddenly whenever words could be merged into a phrase. This may be the neural footprint of “merge,” a fundamental tree-building operation that has been hypothesized to allow for the recursive properties of human language.

Abstract

Although sentences unfold sequentially, one word at a time, most linguistic theories propose that their underlying syntactic structure involves a tree of nested phrases rather than a linear sequence of words. Whether and how the brain builds such structures, however, remains largely unknown. Here, we used human intracranial recordings and visual word-by-word presentation of sentences and word lists to investigate how left-hemispheric brain activity varies during the formation of phrase structures. In a broad set of language-related areas, comprising multiple superior temporal and inferior frontal sites, high-gamma power increased with each successive word in a sentence but decreased suddenly whenever words could be merged into a phrase. Regression analyses showed that each additional word or multiword phrase contributed a similar amount of additional brain activity, providing evidence for a merge operation that applies equally to linguistic objects of arbitrary complexity. More superficial models of language, based solely on sequential transition probability over lexical and syntactic categories, only captured activity in the posterior middle temporal gyrus. Formal model comparison indicated that the model of multiword phrase construction provided a better fit than probability-based models at most sites in superior temporal and inferior frontal cortices. Activity in those regions was consistent with a neural implementation of a bottom-up or left-corner parser of the incoming language stream. Our results provide initial intracranial evidence for the neurophysiological reality of the merge operation postulated by linguists and suggest that the brain compresses syntactically well-formed sequences of words into a hierarchy of nested phrases.

Brain-to-Brain symmetry tracks classroom interactions.

From Dikker et al.:

Highlights

•We report a real-world group EEG study, in a school, during normal class activities 

•EEG was recorded from 12 students simultaneously, repeated over 11 sessions 

•Students’ brain-to-brain group synchrony predicts classroom engagement 

•Students’ brain-to-brain group synchrony predicts classroom social dynamics

Summary

The human brain has evolved for group living. Yet we know so little about how it supports dynamic group interactions that the study of real-world social exchanges has been dubbed the “dark matter of social neuroscience”. Recently, various studies have begun to approach this question by comparing brain responses of multiple individuals during a variety of (semi-naturalistic) tasks. These experiments reveal how stimulus properties, individual differences, and contextual factors may underpin similarities and differences in neural activity across people. However, most studies to date suffer from various limitations: they often lack direct face-to-face interaction between participants, are typically limited to dyads, do not investigate social dynamics across time, and, crucially, they rarely study social behavior under naturalistic circumstances. Here we extend such experimentation drastically, beyond dyads and beyond laboratory walls, to identify neural markers of group engagement during dynamic real-world group interactions. We used portable electroencephalogram (EEG) to simultaneously record brain activity from a class of 12 high school students over the course of a semester (11 classes) during regular classroom activities. A novel analysis technique to assess group-based neural coherence demonstrates that the extent to which brain activity is synchronized across students predicts both student class engagement and social dynamics. This suggests that brain-to-brain synchrony is a possible neural marker for dynamic social interactions, likely driven by shared attention mechanisms. This study validates a promising new method to investigate the neuroscience of group interactions in ecologically natural settings.

Our mental models predict emotion transitions.

Thornton and Tamir (open source) demonstrate that we use mental models to allow us to predict, during a currently perceived emotion in another person, the next one or two emotional transition that person is likely to undergo.

Significance

People naturally understand that emotions predict actions: angry people aggress, tired people rest, and so forth. Emotions also predict future emotions: for example, tired people become frustrated and guilty people become ashamed. Here we examined whether people understand these regularities in emotion transitions. Comparing participants’ ratings of transition likelihood to others’ experienced transitions, we found that raters’ have accurate mental models of emotion transitions. These models could allow perceivers to predict others’ emotions up to two transitions into the future with above-chance accuracy. We also identified factors that inform—but do not fully determine—these mental models: egocentric bias, the conceptual properties of valence, social impact, and rationality, and the similarity and co-occurrence between different emotions.

Abstract

Successful social interactions depend on people’s ability to predict others’ future actions and emotions. People possess many mechanisms for perceiving others’ current emotional states, but how might they use this information to predict others’ future states? We hypothesized that people might capitalize on an overlooked aspect of affective experience: current emotions predict future emotions. By attending to regularities in emotion transitions, perceivers might develop accurate mental models of others’ emotional dynamics. People could then use these mental models of emotion transitions to predict others’ future emotions from currently observable emotions. To test this hypothesis, studies 1–3 used data from three extant experience-sampling datasets to establish the actual rates of emotional transitions. We then collected three parallel datasets in which participants rated the transition likelihoods between the same set of emotions. Participants’ ratings of emotion transitions predicted others’ experienced transitional likelihoods with high accuracy. Study 4 demonstrated that four conceptual dimensions of mental state representation—valence, social impact, rationality, and human mind—inform participants’ mental models. Study 5 used 2 million emotion reports on the Experience Project to replicate both of these findings: again people reported accurate models of emotion transitions, and these models were informed by the same four conceptual dimensions. Importantly, neither these conceptual dimensions nor holistic similarity could fully explain participants’ accuracy, suggesting that their mental models contain accurate information about emotion dynamics above and beyond what might be predicted by static emotion knowledge alone.

A chemical link between early life stress and adult schizophrenia

A massive collaboration finds that schizophrenia-like symptoms induced by early life stress in mice correlates with expression of a DNA altering enzyme. Inhibition of that enzyme (whose levels are also increased in human patients with early life stress) reduces schizophrenia-like symptoms:

Significance

Early life stress (ELS) is an important risk factor for schizophrenia. Our study shows that ELS in mice increases the levels of histone-deacetylase (HDAC) 1 in brain and blood. Although altered Hdac1 expression in response to ELS is widespread, increased Hdac1 levels in the prefrontal cortex are responsible for the development of schizophrenia-like phenotypes. In turn, administration of an HDAC inhibitor ameliorates ELS-induced schizophrenia-like phenotypes. We also show that Hdac1 levels are increased in the brains of patients with schizophrenia and in blood from patients who suffered from ELS, suggesting that the analysis of Hdac1 expression in blood could be used for patient stratification and individualized therapy.

Abstract

Schizophrenia is a devastating disease that arises on the background of genetic predisposition and environmental risk factors, such as early life stress (ELS). In this study, we show that ELS-induced schizophrenia-like phenotypes in mice correlate with a widespread increase of histone-deacetylase 1 (Hdac1) expression that is linked to altered DNA methylation. Hdac1 overexpression in neurons of the medial prefrontal cortex, but not in the dorsal or ventral hippocampus, mimics schizophrenia-like phenotypes induced by ELS. Systemic administration of an HDAC inhibitor rescues the detrimental effects of ELS when applied after the manifestation of disease phenotypes. In addition to the hippocampus and prefrontal cortex, mice subjected to ELS exhibit increased Hdac1 expression in blood. Moreover, Hdac1 levels are increased in blood samples from patients with schizophrenia who had encountered ELS, compared with patients without ELS experience. Our data suggest that HDAC1 inhibition should be considered as a therapeutic approach to treat schizophrenia.

You're less likely to check facts in a social media crowd than when alone.

Jun et al. (open source) make a stab at characterizing the societal problem of "fake" news:

Significance

The dissemination of unverified content (e.g., “fake” news) is a societal problem with influence that can acquire tremendous reach when propagated through social networks. This article examines how evaluating information in a social context affects fact-checking behavior. Across eight experiments, people fact-checked less often when they evaluated claims in a collective (e.g., group or social media) compared with an individual setting. Inducing momentary vigilance increased the rate of fact-checking. These findings advance our understanding of whether and when people scrutinize information in social environments. In an era of rapid information diffusion, identifying the conditions under which people are less likely to verify the content that they consume is both conceptually important and practically relevant.

Abstract

Today’s media landscape affords people access to richer information than ever before, with many individuals opting to consume content through social channels rather than traditional news sources. Although people frequent social platforms for a variety of reasons, we understand little about the consequences of encountering new information in these contexts, particularly with respect to how content is scrutinized. This research tests how perceiving the presence of others (as on social media platforms) affects the way that individuals evaluate information—in particular, the extent to which they verify ambiguous claims. Eight experiments using incentivized real effort tasks found that people are less likely to fact-check statements when they feel that they are evaluating them in the presence of others compared with when they are evaluating them alone. Inducing vigilance immediately before evaluation increased fact-checking under social settings.

Cracking the brain's code for facial identity.

Chang and Tsao appear to have figured out how facial identity is represented in the brain:

Highlights

•Facial images can be linearly reconstructed using responses of ∼200 face cells 

•Face cells display flat tuning along dimensions orthogonal to the axis being coded 

•The axis model is more efficient, robust, and flexible than the exemplar model 

•Face patches ML/MF and AM carry complementary information about faces

Summary

Primates recognize complex objects such as faces with remarkable speed and reliability. Here, we reveal the brain’s code for facial identity. Experiments in macaques demonstrate an extraordinarily simple transformation between faces and responses of cells in face patches. By formatting faces as points in a high-dimensional linear space, we discovered that each face cell’s firing rate is proportional to the projection of an incoming face stimulus onto a single axis in this space, allowing a face cell ensemble to encode the location of any face in the space. Using this code, we could precisely decode faces from neural population responses and predict neural firing rates to faces. Furthermore, this code disavows the long-standing assumption that face cells encode specific facial identities, confirmed by engineering faces with drastically different appearance that elicited identical responses in single face cells. Our work suggests that other objects could be encoded by analogous metric coordinate systems.

From their introduction, their rationale for where they recorded in the inferior temporal cortex (IT):

To explore the geometry of tuning of high-level sensory neurons in a high-dimensional space, we recorded responses of cells in face patches middle lateral (ML)/middle fundus (MF) and anterior medial (AM) to a large set of realistic faces parameterized by 50 dimensions. We chose to record in ML/MF and AM because previous functional and anatomical experiments have demonstrated a hierarchical relationship between ML/MF and AM and suggest that AM is the final output stage of IT face processing. In particular, a population of sparse cells has been found in AM, which appear to encode exemplars for specific individuals, as they respond to faces of only a few specific individuals, regardless of head orientation. These cells encode the most explicit concept of facial identity across the entire face patch system, and understanding them seems crucial for gaining a full understanding of the neural code for faces in IT cortex.

Trust and the poverty trap.

from Jachimowicz et al:

Significance

More than 1.5 billion people worldwide live in poverty. Even in the United States, 14% live below the poverty line. Despite many policies and programs, poverty remains a domestic and global challenge; the number of US households earning less than $2/d nearly doubled in the last 15 y. One reason why the poor remain poor is their tendency to make myopic decisions. With reduced temporal discounting, low-income individuals could invest more in forward-looking educational, financial, and social activities that could alleviate their impoverished situation. We show that increased community trust can decrease temporal discounting in low-income populations and test this mechanism in a 2-y field intervention in rural Bangladesh through a low-cost and scalable method that builds community trust.

Abstract

Why do the poor make shortsighted choices in decisions that involve delayed payoffs? Foregoing immediate rewards for larger, later rewards requires that decision makers (i) believe future payoffs will occur and (ii) are not forced to take the immediate reward out of financial need. Low-income individuals may be both less likely to believe future payoffs will occur and less able to forego immediate rewards due to higher financial need; they may thus appear to discount the future more heavily. We propose that trust in one’s community—which, unlike generalized trust, we find does not covary with levels of income—can partially offset the effects of low income on myopic decisions. Specifically, we hypothesize that low-income individuals with higher community trust make less myopic intertemporal decisions because they believe their community will buffer, or cushion, against their financial need. In archival data and laboratory studies, we find that higher levels of community trust among low-income individuals lead to less myopic decisions. We also test our predictions with a 2-y community trust intervention in rural Bangladesh involving 121 union councils (the smallest rural administrative and local government unit) and find that residents in treated union councils show higher levels of community trust and make less myopic intertemporal choices than residents in control union councils. We discuss the implications of these results for the design of domestic and global policy interventions to help the poor make decisions that could alleviate poverty.

The heart trumps the head : Desirability bias in political belief revision.

From Tappin et al.

Understanding how individuals revise their political beliefs has important implications for society. In a pre-registered study (N=900) we experimentally separated the predictions of two leading theories of human belief revision—desirability bias and confirmation bias—in the context of the 2016 US presidential election. Participants indicated who they desired to win, and who they believed would win, the election. Following confrontation with evidence that was either consistent or inconsistent with their desires or beliefs, they again indicated who they believed would win. We observed a robust desirability bias—individuals updated their beliefs more if the evidence was consistent (versus inconsistent) with their desired outcome. This bias was independent of whether the evidence was consistent or inconsistent with their prior beliefs. In contrast, we find limited evidence of an independent confirmation bias in belief updating. These results have implications for the relevant psychological theories and for political belief revision in practice.

In a NYTimes piece pointing to (marketing) their study, the authors note that:

Our study suggests that political belief polarization may emerge because of peoples’ conflicting desires, not their conflicting beliefs per se. This is rather troubling, as it implies that even if we were to escape from our political echo chambers, it wouldn’t help much. Short of changing what people want to believe, we must find other ways to unify our perceptions of reality.

Opioids regulate oxytocin enhancement of social attention.

From Monte et al. work suggesting that the effectiveness of oxytocin in treating social dysfunction might be enhanced by the simultaneous administration of opioid blockers.

Significance

In the past decade, there has been an increase in studies using oxytocin (OT) for improving social cognition, but results have been inconsistent. In this study, we took advantage of the physiological relationship between the opioid and OT systems and tested the benefit of administering OT under simultaneously induced opioid antagonism during dyadic gaze interactions. Coadministration of OT and opioid blocker leads to supralinear enhancement of prolonged and selective attention to a live partner and increases interactive gaze after critical social events. Furthermore, we provide neurogenetic evidence in the human brain supporting the interaction between specific opioid receptor genes and the genes for OT processing. Our results suggest a new avenue for amplifying the efficacy of OT in clinical populations.

Abstract

To provide new preclinical evidence toward improving the efficacy of oxytocin (OT) in treating social dysfunction, we tested the benefit of administering OT under simultaneously induced opioid antagonism during dyadic gaze interactions in monkeys. OT coadministered with a μ-opioid receptor antagonist, naloxone, invoked a supralinear enhancement of prolonged and selective social attention, producing a stronger effect than the summed effects of each administered separately. These effects were consistently observed when averaging over entire sessions, as well as specifically following events of particular social importance, including mutual eye contact and mutual reward receipt. Furthermore, attention to various facial regions was differentially modulated depending on social context. Using the Allen Institute’s transcriptional atlas, we further established the colocalization of μ-opioid and κ-opioid receptor genes and OT genes at the OT-releasing sites in the human brain. These data across monkeys and humans support a regulatory relationship between the OT and opioid systems and suggest that administering OT under opioid antagonism may boost the therapeutic efficacy of OT for enhancing social cognition.

Visual category selectivity is innate.

Interesting work from Hurk et al., who find that the brains of people blind since birth show category specific activity patterns for faces, scenes, body parts, and objects, meaning that this functional brain organization does not depend on visual input during development.

Significance

The brain’s ability to recognize visual categories is guided by category-selective ventral-temporal cortex (VTC). Whether visual experience is required for the functional organization of VTC into distinct functional subregions remains unknown, hampering our understanding of the mechanisms that drive category recognition. Here, we demonstrate that VTC in individuals who were blind since birth shows robust discriminatory responses to natural sounds representing different categories (faces, scenes, body parts, and objects). These activity patterns in the blind also could predict successfully which category was visually perceived by controls. The functional cortical layout in blind individuals showed remarkable similarity to the well-documented layout observed in sighted controls, suggesting that visual functional brain organization does not rely on visual input.

Abstract

To what extent does functional brain organization rely on sensory input? Here, we show that for the penultimate visual-processing region, ventral-temporal cortex (VTC), visual experience is not the origin of its fundamental organizational property, category selectivity. In the fMRI study reported here, we presented 14 congenitally blind participants with face-, body-, scene-, and object-related natural sounds and presented 20 healthy controls with both auditory and visual stimuli from these categories. Using macroanatomical alignment, response mapping, and surface-based multivoxel pattern analysis, we demonstrated that VTC in blind individuals shows robust discriminatory responses elicited by the four categories and that these patterns of activity in blind subjects could successfully predict the visual categories in sighted controls. These findings were confirmed in a subset of blind participants born without eyes and thus deprived from all light perception since conception. The sounds also could be decoded in primary visual and primary auditory cortex, but these regions did not sustain generalization across modalities. Surprisingly, although not as strong as visual responses, selectivity for auditory stimulation in visual cortex was stronger in blind individuals than in controls. The opposite was observed in primary auditory cortex. Overall, we demonstrated a striking similarity in the cortical response layout of VTC in blind individuals and sighted controls, demonstrating that the overall category-selective map in extrastriate cortex develops independently from visual experience.

Preferences for group dominance underlie social inequality and violence across societies

Work of Kunst et al. provided in open source text  whose findings suggest that societal inequality is reflected in people’s minds as dominance motives that underpin ideologies and actions that ultimately sustain group-based hierarchy.:

Significance

Individuals differ in the degree to which they endorse group-based hierarchies in which some social groups dominate others. Much research demonstrates that among individuals this preference robustly predicts ideologies and behaviors enhancing and sustaining social hierarchies (e.g., racism, sexism, and prejudice). Combining aggregate archival data from 27 countries (n = 41,824) and multilevel data from 30 US states (n = 4,613) with macro-level indicators, we demonstrate that the degree of structural inequality, social instability, and violence in different countries and US states is reflected in their populations’ minds in the form of support of group-based hegemony. This support, in turn, increases individual endorsement of ideologies and behaviors that ultimately sustain group-based inequality, such as the ethnic persecution of immigrants.

Abstract

Whether and how societal structures shape individual psychology is a foundational question of the social sciences. Combining insights from evolutionary biology, economy, and the political and psychological sciences, we identify a central psychological process that functions to sustain group-based hierarchies in human societies. In study 1, we demonstrate that macrolevel structural inequality, impaired population outcomes, socio-political instability, and the risk of violence are reflected in the endorsement of group hegemony at the aggregate population level across 27 countries (n = 41,824): The greater the national inequality, the greater is the endorsement of between-group hierarchy within the population. Using multilevel analyses in study 2, we demonstrate that these psychological group-dominance motives mediate the effects of macrolevel functioning on individual-level attitudes and behaviors. Specifically, across 30 US states (n = 4,613), macrolevel inequality and violence were associated with greater individual-level support of group hegemony. Crucially, this individual-level support, rather than cultural-societal norms, was in turn uniquely associated with greater racism, sexism, welfare opposition, and even willingness to enforce group hegemony violently by participating in ethnic persecution of subordinate out-groups. These findings suggest that societal inequality is reflected in people’s minds as dominance motives that underpin ideologies and actions that ultimately sustain group-based hierarchy.

The wisdom of crowds for visual search.

Juni and Eckstein show that perceptual decisions about large image data sets (as from medical and geospatial imaging) that are made by a group are more likely to be correct if group members' confidences are averaged than if a simple majority vote is taken:

Significance

Simple majority voting is a widespread, effective mechanism to exploit the wisdom of crowds. We explored scenarios where, from decision to decision, a varying minority of group members often has increased information relative to the majority of the group. We show how this happens for visual search with large image data and how the resulting pooling benefits are greater than previously thought based on simpler perceptual tasks. Furthermore, we show how simple majority voting obtains inferior benefits for such scenarios relative to averaging people’s confidences. These findings could apply to life-critical medical and geospatial imaging decisions that require searching large data volumes and, more generally, to any decision-making task for which the minority of group members with high expertise varies across decisions.

Abstract

Decision-making accuracy typically increases through collective integration of people’s judgments into group decisions, a phenomenon known as the wisdom of crowds. For simple perceptual laboratory tasks, classic signal detection theory specifies the upper limit for collective integration benefits obtained by weighted averaging of people’s confidences, and simple majority voting can often approximate that limit. Life-critical perceptual decisions often involve searching large image data (e.g., medical, security, and aerial imagery), but the expected benefits and merits of using different pooling algorithms are unknown for such tasks. Here, we show that expected pooling benefits are significantly greater for visual search than for single-location perceptual tasks and the prediction given by classic signal detection theory. In addition, we show that simple majority voting obtains inferior accuracy benefits for visual search relative to averaging and weighted averaging of observers’ confidences. Analysis of gaze behavior across observers suggests that the greater collective integration benefits for visual search arise from an interaction between the foveated properties of the human visual system (high foveal acuity and low peripheral acuity) and observers’ nonexhaustive search patterns, and can be predicted by an extended signal detection theory framework with trial to trial sampling from a varying mixture of high and low target detectabilities across observers (SDT-MIX). These findings advance our theoretical understanding of how to predict and enhance the wisdom of crowds for real world search tasks and could apply more generally to any decision-making task for which the minority of group members with high expertise varies from decision to decision.

Listener evaluations of new and old Italian violins

From Fritz et al.:

Old Italian violins are routinely credited with playing qualities supposedly unobtainable in new instruments. These qualities include the ability to project their sound more effectively in a concert hall—despite seeming relatively quiet under the ear of the player—compared with new violins. Although researchers have long tried to explain the “mystery” of Stradivari’s sound, it is only recently that studies have addressed the fundamental assumption of tonal superiority. Results from two studies show that, under blind conditions, experienced violinists tend to prefer playing new violins over Old Italians. Moreover, they are unable to tell new from old at better than chance levels. This study explores the relative merits of Stradivari and new violins from the perspective of listeners in a hall. Projection and preference are taken as the two broadest criteria by which listeners might meaningfully compare violins. Which violins are heard better, and which are preferred? In two separate experiments, three new violins were compared with three by Stradivari. Projection was tested both with and without orchestral accompaniment. Projection and preference were judged simultaneously by dividing listeners into two groups. Results are unambiguous. The new violins projected better than the Stradivaris whether tested with orchestra or without, the new violins were generally preferred by the listeners, and the listeners could not reliably distinguish new from old. The single best-projecting violin was considered the loudest under the ear by players, and on average, violins that were quieter under the ear were found to project less well.

Solitary discourse yields deeper understanding than solitary description.

Zavals and Kuhn show that imagining a discourse between advocates of two political candidates yields a richer representation than solitary evaluation of the candidates' merits:

Young adults received information regarding the platforms of two candidates for mayor of a troubled city. Half constructed a dialogue between advocates of the candidates, and the other half wrote an essay evaluating the candidates’ merits. Both groups then wrote a script for a TV spot favoring their preferred candidate. Results supported our hypothesis that the dialogic task would lead to deeper, more comprehensive processing of the two positions, and hence a richer representation of them. The TV scripts of the dialogue group included more references to city problems, candidates’ proposed actions, and links between them, as well as more criticisms of proposed actions and integrative judgments extending across multiple problems or proposed actions. Assessment of levels of epistemological understanding administered to the two groups after the writing tasks revealed that the dialogic group exhibited a lesser frequency of the absolutist position that knowledge consists of facts knowable with certainty. The potential of imagined interaction as a substitute for actual social exchange is considered.

Detecting both facial and olfactory cues of sickness in others

From Regenbogen et al.:

Significance

In the perpetual race between evolving organisms and pathogens, the human immune system has evolved to reduce the harm of infections. As part of such a system, avoidance of contagious individuals would increase biological fitness. The present study shows that we can detect both facial and olfactory cues of sickness in others just hours after experimental activation of their immune system. The study further demonstrates that multisensory integration of these olfactory and visual sickness cues is a crucial mechanism for how we detect and socially evaluate sick individuals. Thus, by motivating the avoidance of sick conspecifics, olfactory–visual cues, both in isolation and integrated, may be important parts of circuits handling imminent threats of contagion.

Abstract

Throughout human evolution, infectious diseases have been a primary cause of death. Detection of subtle cues indicating sickness and avoidance of sick conspecifics would therefore be an adaptive way of coping with an environment fraught with pathogens. This study determines how humans perceive and integrate early cues of sickness in conspecifics sampled just hours after the induction of immune system activation, and the underlying neural mechanisms for this detection. In a double-blind placebo-controlled crossover design, the immune system in 22 sample donors was transiently activated with an endotoxin injection [lipopolysaccharide (LPS)]. Facial photographs and body odor samples were taken from the same donors when “sick” (LPS-injected) and when “healthy” (saline-injected) and subsequently were presented to a separate group of participants (n = 30) who rated their liking of the presented person during fMRI scanning. Faces were less socially desirable when sick, and sick body odors tended to lower liking of the faces. Sickness status presented by odor and facial photograph resulted in increased neural activation of odor- and face-perception networks, respectively. A superadditive effect of olfactory–visual integration of sickness cues was found in the intraparietal sulcus, which was functionally connected to core areas of multisensory integration in the superior temporal sulcus and orbitofrontal cortex. Taken together, the results outline a disease-avoidance model in which neural mechanisms involved in the detection of disease cues and multisensory integration are vital parts.

Optimal incentives for collective intelligence

Mann and Helbing devise a game-theoretic model of collective prediction showing that an antidote to groupthink and conformity is to reward those who have shown accuracy when the majority opinion has been in error:

Significance

Diversity of information and expertise among group members has been identified as a crucial ingredient of collective intelligence. However, many factors tend to reduce the diversity of groups, such as herding, groupthink, and conformity. We show why the individual incentives in financial and prediction markets and the scientific community reduce diversity of information and how these incentives can be changed to improve the accuracy of collective forecasting. Our results, therefore, suggest ways to improve the poor performance of collective forecasting seen in recent political events and how to change career rewards to make scientific research more successful.

Abstract

Collective intelligence is the ability of a group to perform more effectively than any individual alone. Diversity among group members is a key condition for the emergence of collective intelligence, but maintaining diversity is challenging in the face of social pressure to imitate one’s peers. Through an evolutionary game-theoretic model of collective prediction, we investigate the role that incentives may play in maintaining useful diversity. We show that market-based incentive systems produce herding effects, reduce information available to the group, and restrain collective intelligence. Therefore, we propose an incentive scheme that rewards accurate minority predictions and show that this produces optimal diversity and collective predictive accuracy. We conclude that real world systems should reward those who have shown accuracy when the majority opinion has been in error.

Poor human olfaction is a 19th-century myth

A review from McGann noting work that shows no anatomical basis for supposing human olfaction to be inferior to animals, although variation in the olfactory receptor molecules in different species does cause differences in which odors are best detected:

Structured Abstract

BACKGROUND

It is widely believed that the human sense of smell is inferior to that of other mammals, especially rodents and dogs. This Review traces the scientific history of this idea to 19th-century neuroanatomist Paul Broca. He classified humans as “nonsmellers” not owing to any sensory testing but because he believed that the evolutionary enlargement of the human frontal lobe gave human beings free will at the expense of the olfactory system. He especially emphasized the small size of the human brain’s olfactory bulb relative to the size of the brain overall, and noted that other mammals have olfactory bulbs that are proportionately much larger. Broca’s claim that humans have an impoverished olfactory system (later labeled “microsmaty,” or tiny smell) influenced Sigmund Freud, who argued that olfactory atrophy rendered humans susceptible to mental illness. Humans’ supposed microsmaty led to the scientific neglect of the human olfactory system for much of the 20th century, and even today many biologists, anthropologists, and psychologists persist in the erroneous belief that humans have a poor sense of smell. Genetic and neurobiological data that reveal features unique to the human olfactory system are regularly misinterpreted to underlie the putative microsmaty, and the impact of human olfactory dysfunction is underappreciated in medical practice.

ADVANCES

Although the human olfactory system has turned out to have some biological differences from that of other mammalian species, it is generally similar in its neurobiology and sensory capabilities. The human olfactory system has fewer functional olfactory receptor genes than rodents, for instance, but the human brain has more complex olfactory bulbs and orbitofrontal cortices with which to interpret information from the roughly 400 receptor types that are expressed. The olfactory bulb is proportionately smaller in humans than in rodents, but is comparable in the number of neurons it contains and is actually much larger in absolute terms. Thus, although the rest of the brain became larger as humans evolved, the olfactory bulb did not become smaller. When olfactory performance is compared experimentally between humans and other animals, a key insight has been that the results are strongly influenced by the selection of odors tested, presumably because different odor receptors are expressed in each species. When an appropriate range of odors is tested, humans outperform laboratory rodents and dogs in detecting some odors while being less sensitive to other odors. Like other mammals, humans can distinguish among an incredible number of odors and can even follow outdoor scent trails. Human behaviors and affective states are also strongly influenced by the olfactory environment, which can evoke strong emotional and behavioral reactions as well as prompting distinct memories. Odor-mediated communication between individuals, once thought to be limited to “lower animals,” is now understood to carry information about familial relationships, stress and anxiety levels, and reproductive status in humans as well, although this information is not always consciously accessible.

OUTLOOK

The human olfactory system is increasingly understood to be highly dynamic. Olfactory sensitivity and discrimination abilities can be changed by experiences like environmental odor exposure or even just learning to associate odors with other stimuli in the laboratory. The neurobiological underpinnings of this plasticity, including “bottom-up” factors like regulation of peripheral odor receptors and “top-down” factors like the sensory consequences of emotional and cognitive states, are just beginning to be understood. The role of olfactory communication in shaping social interactions is also actively being explored, including the social spread of emotion through olfactory cues. Finally, impaired olfaction can be a leading indicator of certain neurodegenerative diseases, notably Parkinson’s disease and Alzheimer’s disease. New experimentation will be required to understand how olfactory sequelae might also reflect problems elsewhere in the nervous system, including mental disorders with sensory symptomatology. The idea that human smell is impoverished compared to other mammals is a 19th-century myth.