Reviewing theory and experimental evidence, they suggest that spontaneous BOLD activity may be more closely aligned with off-line plasticity and homeostatic processes than on-line fluctuations in cognitive content

Brain activity is not only for thinking. Timothy OLaumann, Abraham ZSnyder. Current Opinion in Behavioral Sciences, Volume 40, August 2021, Pages 130-136. https://doi.org/10.1016/j.cobeha.2021.04.002

Abstract: The human brain is a complex organ with multiple competing imperatives. It must perceive and interpret the world, incorporate new information, and maintain its functional integrity over the lifespan. Neural activity is associated with all of these processes. Spontaneous BOLD signals have been invoked as representing neural activity associated with all of these processes. However, their exact role in these processes remains controversial. Here, we review learning machine theory, molecular mechanisms of synaptic plasticity and homeostasis, and recent experimental evidence to suggest that spontaneous BOLD activity may be more closely aligned with off-line plasticity and homeostatic processes than on-line fluctuations in cognitive content.

Introduction

The existence of unceasing spontaneous brain activity has been recognized since at least the 1930s [1]. However, the functions of this activity have remained mysterious [2]. Over the last three decades, blood oxygen level dependent (BOLD) fMRI has become the dominant tool for measurement of brain activity in humans. Soon after the adoption of fMRI, it was observed that fMRI signals exhibit constant fluctuations unrelated to the task [3]. In the context of task fMRI, this activity was conventionally regarded as ‘physiological noise’ [4]. However, it is now clear that this ‘physiological noise’ is temporally correlated within functional systems [5,6]. It is this property of spontaneous brain activity that constitutes the basis of resting state functional connectivity (RSFC) [7]. The existence of this well-structured organization implies that spontaneous brain activity is physiologically consequential.

The meaning of spontaneous BOLD signal fluctuations has been variably interpreted along two different perspectives. According to one view, spontaneous BOLD fluctuations are proposed to reflect unconstrained cognitive processes, for example, retrospection, prospection, reflection, environmental monitoring — the ‘stream of consciousness’ — attendant to our subjective experience. Given the centrality of perception and action to mental life, it is appealing to assume that all observed brain activity is directly related to moment-to-moment cognition and behavior. This perspective has been reinforced by a massive accumulation of PET and fMRI experiments in which brain activity has been imaged with the objective of localizing cognitive operations [8]. More recently, the observation of ‘dynamic’ functional connectivity during wakeful rest and changes in functional connectivity between rest and task states have, at times, been interpreted as reflecting cognition [9,10].

We have previously articulated several problems with the notion that all ongoing BOLD activity directly reflects cognition and behavior (Box 1; [11]): (1) The topography of BOLD fMRI correlations remains largely intact during slow-wave sleep [12] and even anesthesia [13], states in which cognition is presumed to be either absent or greatly attenuated; (2) The extent to which task paradigms modify the correlation structure of spontaneous BOLD signal fluctuations is very limited [14,15,16•]; (3) While unconstrained cognition might be expected to vary from scan to scan within an individual, RSFC remains remarkably consistent across sessions [17,18]. RSFC is also relatively stable within a given scan, discounting fluctuations attributable to drowsiness [11] or arousal [19], which likely relate to fluctuations in BOLD signals, at least partly due to alterations in respiratory behavior and pCO2 [20]. Moreover, brain metabolic activity is high at all times and minimally affected by task performance [21].

Box 1

Evidence that RSFC structure is largely independent of cognitive content

1.

RSFC structure is similar during wake and sleep. For instance, DMN structure is observed through wake, S1, S2, and SWS [12,100].

2.

RSFC structure is present under anesthesia [13,101], although covariance does diminish with increased sedation [102].

3.

RSFC structure is minimally altered by task state [14, 15].

4.

RSFC structure within subject is consistent across sessions [16,11,103].

5.

RSFC structure within subject is similar over long time scales [18,17].

6.

RSFC structure is consistent across subjects at the population level [104,105].

7.

Similar RSFC structure is evident across mammalian species [106, 107, 108].

For all of these reasons, unconstrained cognition does not fully explain ongoing spontaneous activity. An alternative view proposes that spontaneous BOLD activity may more closely relate to mechanisms associated with learning and memory [22•,23]. In the following, we review prior literature supporting the perspective that a substantial fraction of spontaneous brain activity represents homeostatic and consolidative signaling, the function of which is to enable neural plasticity while maintaining the brain's functional integrity through time. We also review recent evidence that BOLD RSFC may be intimately tied to these processes.

Learning machine theory

When considering the role of ongoing neural activity in brain function, it is important to recognize that one of the brain’s primary capacities is its ability to learn new information about its environment. Theoretical considerations, initially formulated by David Marr [24], suggest that any associative learning machine functions optimally if it is allowed to alternate between two states: (1) a learning phase, during which the machine is connected to inputs and connections are enhanced between simultaneously active elements and (2) a restorative phase during which the machine is disconnected from inputs and connections between elements are rebalanced in a manner that increases randomness (entropy) [25,26•]. In multi-layer perceptrons, this principle is expressed as iterative alternation between a forward phase, during which prediction error is evaluated, and a backward phase, during which connection weights are adjusted by back-propagation [27]. The starkest expression of the state alternation principle in living organisms is sleep versus wake. This alternation appears to be necessary: all organisms capable of learning alternate between wake versus sleep states [28]. In vertebrates, events experienced during wake are registered in the hippocampus and the cerebral cortex [29,30]. During slow wave sleep (SWS), reactivation of the same circuits leads to the creation of stable (consolidated) episodic memory [31•].

Understanding how state alternation is implemented in brains requires consideration of the cellular and molecular events underlying synaptic weight modification. Activity-dependent synaptic plasticity plays a crucial role in brain development well before birth [32, 33, 34]. For example, retino-tectal connections have been shown to be sculpted by spontaneous retinal waves during prenatal development of the visual system [35]. Following birth, spontaneous activity continues to refine neural connections using sensory feedback [36,37]. During early life critical periods, experience-dependent synaptic plasticity tunes the response properties of cortical sensory neurons (e.g. ocular dominance columns) [38]. As the brain matures, metabolic ‘brakes’ limit neural plasticity to mechanisms centered on inhibitory interneurons [39, 40, 41]. Although neural plasticity in adults is more restricted, the underlying activity-dependent processes likely follow similar principles.

Molecular mechanisms of activity-dependent synaptic plasticity

Activity-dependent synaptic plasticity is conventionally discussed under the headings of long-term potentiation (LTP) and long-term depression (LTD). But LTP/LTD are deceptively simple terms encompassing a wide range of molecular processes [42,43]. The early phase of LTP (E-LTP) is triggered by Ca2+ influx linked to post-synaptic depolarization, which sets in motion molecular cascades mediated by phosphorylation and dephosphorylation of regulatory molecules (e.g. protein kinase C (PKC) and Ca2+-calmodulin-dependent protein kinase (CamKII)) that govern neurotransmitter receptor trafficking. E-LTP lasts 1−3 hours and is independent of gene expression. The late phase of LTP (L-LTP) begins with the transcription of immediate early genes (IEGs; e.g. Arc, Zif268) that control translational processes, which lead, on a time scale of hours, to structural changes in dendritic spines [44, 45, 46]. Thus, whereas electrophysiological event-related responses may last up to a few hundred millisec and BOLD hemodynamic responses typically evolve over ∼16−20 s, the metabolic traces of the evoked activity persist over much longer time scales. These traces may underlie the observation that fMRI responses to task A are modulated by having performed unrelated task B during the past half hour [47].

The Hebbian principle (‘fire together → wire together’) is often invoked to account for resting state functional connectivity [48,49]. The mechanism underlying Hebbian learning, that is, spike-timing dependent synaptic plasticity (STDP), has been elucidated in considerable detail [50,51]. In brief, neural back-propagation of depolarization induced by a first excitatory stimulus removes the Mg2+ block at NMDA receptors, thereby allowing a second stimulus (if it occurs within a 20–85 ms window) to induce local Ca2+ entry, which initiates the LTP molecular cascade, ultimately reinforcing the association between the paired stimuli. Hebbian mechanisms undoubtedly play a central role in adult learning. Accordingly, it is reasonable to posit that synchronous spontaneous BOLD fluctuations that give rise to RSFC are due to a history of prior co-activation. However, a system dominated by unopposed Hebbian plasticity inevitably becomes either infinitely active or silent.

In contrast to Hebbian plasticity, which adjusts synaptic weights in the same direction as an applied stimulus, the brain also employs various mechanisms of homeostatic plasticity, which adjusts synaptic strengths in the opposite direction to return excitatory/inhibitory (E/I) balance and mean firing rate to prior set points [52]. Homeostatic plasticity includes cell-autonomous mechanisms that directly adjust neuronal excitability to counteract environmental stimuli, as well as multiplicative synaptic scaling, which preserves relative strengths between neighboring synapses, thereby maintaining currently represented information [53•]. These homeostatic mechanisms operate at the level of dendritic branches [45], individual neurons [53•], and large-scale circuits [54], and are active over multiple time scales [55,56]. A correlate of these homeostatic processes is ongoing turnover of synaptic proteins and lipids with half-lives on the order of ‘minutes, hours, days, weeks’ [57]. Modeling experiments suggest that homeostatic regulation of E/I balance plays a crucial role in maintaining the characteristic features of spontaneous brain activity [58]. Importantly, synaptic homeostasis is inseparable from consolidation, the process whereby brief changes in neural activity ultimately lead to stable memory [59,60•]. Thus, it is reasonable to posit that spontaneous activity includes both Hebbian and homeostatic signaling.

There is encouraging evidence of an association between low total cholesterol and aggression towards others as well as suicidality in schizophrenia; association was strongest for low total cholesterol

How do lipids influence risk of violence, self-harm and suicidality in people with psychosis? A systematic review. Piyal Sen et al. Australian & New Zealand Journal of Psychiatry, July 9, 2021. https://doi.org/10.1177/00048674211025608

Abstract

Objectives: Low cholesterol has been linked with violent and suicidal behaviour in people with schizophrenia. This association, if consistently present, may be a promising biological marker that could assist clinicians in decision making regarding risk and treatment. We conducted a systematic review to assess whether there is a reliable association between lipid profile (total cholesterol, high- and low-density lipoprotein cholesterol, and triglycerides) and aggression, self-harm or suicide in people with schizophrenia, and whether effects are similar in males and females.

Method: Relevant databases were searched to identify primary research studies (up to November 2020) that (1) involved adults (some samples also included 16- to 18-year olds) with a confirmed diagnosis of schizophrenia, schizoaffective disorder or psychosis; and (2) included a standardised assessment of verbal aggression, physical aggression against objects, physical aggression against self (including suicide) or others. The search yielded 23 studies eligible for inclusion following a quality appraisal.

Results: Suicidality was the most commonly assessed subtype of aggression (20 studies). For suicidality, about half the studies, including the study with the largest sample size, found a link with total cholesterol. An association between low total cholesterol and violence towards others was found in six of nine studies that investigated this. The evidence for a link with violence was the strongest for total cholesterol, followed by low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, and the weakest for triglycerides. Only a few studies investigated sex differences and yielded mixed evidence. Studies focussed on self-harm as well as involving females in forensic settings were lacking.

Conclusion: There is encouraging evidence of an association between low total cholesterol and aggression towards others as well as suicidality in schizophrenia. Future studies should systematically explore this association in people with schizophrenia who have a significant history of violence, suicidality and self-harm, both inpatients and community, and also investigate underlying mechanisms.

Keywords: Cholesterol, aggression, suicide, schizophrenia, sex

Discussion

There were three main findings in relation to the primary objectives of this systematic review.

First, there were many more studies which reported on a link between low cholesterol and violence to others than those which did not find a link. All researchers investigating forensic samples found such a relationship. However, the relationship was not only with low TC but also with other parameters of the lipid profile, such as low LDL and low HDL. It is thus important not just to collect data on TC, but LDL and HDL as well. The evidence was weaker for the link between TG and violence, with only two studies finding a link, but one with high TG, the other with low TG. It is to be noted that the study with the largest sample size failed to find a link (Hjell et al., 2020). However, one of the issues in this study was the relatively low rate of baseline violence in the study population, thus offering some indication that the link is likely to be more valid in groups where there is a greater prevalence of violence (i.e. forensic populations).

The biological mechanism behind cholesterol–violence association has been hypothesised to involve serotonin. Animal studies have found an increase in violent behaviour in monkeys assigned to a low-cholesterol diet (Kaplan et al., 1991, 1994). Kaplan et al. (1991) suggested that low cholesterol may reduce cell viscosity and reduce serotonergic receptor activity. This may lead to a depressive state (Marcinko et al., 2005), increased impulsivity (Carver and Miller, 2006; Paaver et al., 2007) and aggressive behaviour (Chakrabarti et al., 2004). This finding was observed in Kaplan et al. (1994), where monkeys with experimentally lowered cholesterol had higher concentrations of serotonin metabolites than monkeys given high-cholesterol diets. However, the exact biological mechanism underlying cholesterol–violence (towards self/others) association in humans is still unclear.

Second, there was mixed evidence for a link between low cholesterol and suicidality in schizophrenia, with almost equal number of studies in favour and against such a link. The majority of studies used suicide as the method of assessing aggression. Eight studies found a statistically significant association between low cholesterol and suicide attempts, two of which only found this association in females (Misiak et al., 2015; Shrivastava et al., 2017). Seven studies failed to find a link. However, the study with the largest sample size (Sankaranarayan et al., 2020) did find a link, thus suggesting that methodological flaws, particularly low power, might have contributed to the variation in findings.

The evidence for a specific relationship between lipid profile and violent suicidal attempts was even more mixed. Ruljancic et al. (2007) found a significant association between low cholesterol and non-violent suicide attempts, in contrast to two other studies (Marcinko et al., 2005; Tripodianakis et al., 2002), reporting an association between low cholesterol and violent suicide attempts. While the two studies showing a positive association had smaller sample sizes, such findings are supported by other literature (Garland et al., 2000; Vevera et al., 2003). A meta-analysis found 50% more violent deaths in males with relatively low cholesterol than in participants with higher levels of cholesterol (Jacobs et al., 1992). This meta-analysis also found a higher prevalence of depressive symptoms in males with low serum cholesterol.

An association between low cholesterol and depression has frequently been observed (Grussu et al., 2007; Ploeckinger et al., 1996; Troisi et al., 2002). It is plausible that the causal pathway from low cholesterol to suicidality in schizophrenia patients involves depression. Kunugi et al. (1997) did not find a significant difference in cholesterol level between suicidal and non-suicidal inpatients with schizophrenia spectrum disorders. However, significantly lower cholesterol levels were found in suicide attempters with mood disorders compared with controls. Similarly, Modai et al. (1994) found a significant association between lower cholesterol and suicidality in patients with depression, but not in schizophrenia patients. Around 40% of people with schizophrenia have depression, with depression being the most significant factor in completed suicide (Upthegrove et al., 2016). People with schizophrenia and comorbid depression also have a significantly increased risk of violence and suicidality (Conley et al., 2007) and poorer clinical outcomes (Gardsjord et al., 2016; Upthegrove et al., 2009). The studies included in this systematic review did not control for depressive symptoms in schizophrenia patients. Although findings of low cholesterol and depression are inconsistent, with a number of researchers not finding a significant association (Cepeda et al., 2020; Van Dam et al., 1999), it is plausible that suicidality seen in schizophrenia patients with low cholesterol may be a consequence of depressive symptoms.

Third, most of the studies had similar findings for males and females. However, low HDL was seen in two studies to be a better predictor of violence than low TC for males (Eriksen et al., 2017, 2018). Another study found female sex and low TC levels could be used, in part, as predictors of violence in patients with schizophrenia (Chen et al., 2015). One study found higher TC and LDL levels to be associated with suicidality in females but not males with first-episode schizophrenia, thus suggesting that the link between lipids and violence is somewhat complex (Misiak et al., 2015). Future studies need to be designed to explore the nature of the link separately for females and males. All studies (Chakrabarti et al., 2004; Marcinko et al., 2005, 2007, 2008; Repo-Tiihonen et al., 2002) investigating only male schizophrenia patients found a significant association between low cholesterol and suicidality, except one group (Turkoglu et al., 2009) who did not report a significant association. On the contrary, three study authors observed an association only in female participants: two for suicidality (Misiak et al., 2015; Shrivastava et al., 2017) and one for violence towards others in patients with schizophrenia (Chen et al., 2015). However, one study (Eriksen et al., 2017) did not find this specific correlation in female participants.

Thus, it can be concluded that cholesterol levels could be used, in part, as predictors of violence in patients with schizophrenia. The evidence for a clear link with sex remains inconclusive. This is an important area for further work given that rates of violence in psychiatric patients following discharge tend to be higher in men than in women (Robbins et al., 2003). In addition, the neurobiology of violence, factors like body mass index (BMI), incidence of metabolic syndrome following antipsychotic medication and the effects of cholesterol are different between men and women, suggesting that discrete effects may occur in each sex (Golomb, 1998).

Limitations

There were several limitations regarding the studies reviewed. First, in many of the studies reviewed, the main focus was on suicide and physical aggression to others. As a result, most patients observed were clinically ill enough to warrant inpatient treatment. Few studies evaluated aggression as physical against property and verbal, potentially deemed less severe and more likely to be seen in community or outpatient-based studies. A representative view of schizophrenia patients of all severities, including inpatients and outpatients, was therefore not specifically assessed in this review. Second, confounding factors, including sex, medication and age, may have affected the findings of this review. According to the Gender Paradox in Suicide, men are more likely to die by suicide than women, while women are more likely to engage in suicidal behaviour and deliberate self-harm (Canetto and Sakinofsky, 1998). However, self-harm was not frequently assessed in these studies. There is some indication of a link between low TC, HDL, LDL and impulsivity, which could translate into risk of self-harm, but this link needs to be explored through studies in populations with higher self-harming behaviours, like inpatient female wards. Medication, such as certain antipsychotics like risperidone, stimulate serotonergic output in cortical and subcortical areas more than other antipsychotics (Amato, 2015), and this may contribute to changes in aggressive behaviour independent of cholesterol level. In addition, with age comes a natural variance in cholesterol level, with a tendency of increased serum cholesterol with increasing age (Morgan et al., 2016). Aggressive behaviour may be independent of low cholesterol in younger participants as they, typically, would have a lower cholesterol level when compared to older patients. The effects of age as well as medication were not accounted for in a number of studies. Finally, the lack of statistical analysis using a 95% confidence interval in a number of studies (see Table 4) limited the review by making it difficult to assess precision and risk in data obtained.

In addition, there are limitations to the review itself. First, the review may have been limited by only allowing diagnosis of schizophrenia by a variant of DSM or ICD classifications. This excluded foreign classifications such as T-SCL-90-R. Second, selection bias arose when only considering studies reported in English. The inclusion and exclusion criteria stated that participants must be adults only, unless unavoidable. As a result, three included studies (Chen et al., 2015; Repo-Tiihonen et al., 2002; Ruljancic et al., 2007) had some participants below the age of 18, leading to wide variations in the age range of the study participants.

Sweden: Parental absences tend to be associated with earlier first births, and more reliably so for women; recent changes in effects may mean that fathers start influencing sons and daughters more similarly

Historical Context Changes Pathways of Parental Influence on Reproduction: An Empirical Test from 20th-Century Sweden. Cristina Moya et al. Soc. Sci. 2021, 10(7), 260, Jul 8 2021. https://doi.org/10.3390/socsci10070260

Abstract: Several studies have found that parental absences in childhood are associated with individuals’ reproductive strategies later in life. However, these associations vary across populations and the reasons for this heterogeneity remain debated. In this paper, we examine the diversity of parental associations in three ways. First, we test whether different kinds of parental availability in childhood and adolescence are associated with women’s and men’s ages at first birth using the intergenerational and longitudinal Uppsala Birth Cohort Study (UBCoS) dataset from Sweden. This cultural context provides a strong test of the hypothesis that parents influence life history strategies given that robust social safety nets may buffer parental absences. Second, we examine whether investments in education help explain why early parental presence is associated with delayed ages at first birth in many post-industrial societies, given that parents often support educational achievement. Third, we compare parental associations with reproductive timing across two adjacent generations in Sweden. This historical contrast allows us to control for many sources of heterogeneity while examining whether changing educational access and norms across the 20th-century change the magnitude and pathways of parental influence. We find that parental absences tend to be associated with earlier first births, and more reliably so for women. Many of these associations are partially mediated by university attendance. However, we also find important differences across cohorts. For example, the associations with paternal death become similar for sons and daughters in the more recent cohort. One possible explanation for this finding is that fathers start influencing sons and daughters more similarly. Our results illustrate that historical changes within a population can quickly shift how family affects life history.

Keywords: fertility; reproductive timing; family structure; life history strategies; educational attainment; cohort effects

Sex differences are consistent in rest state fMRI and should be considered seriously in any study; features that discriminate males and females were found to be distributed across several different brain regions

Machine Learning Evidence for Sex Differences Consistently Influences Resting-State fMRI Fluctuations Across Multiple Independently-Acquired Datasets. Obada Al Zoubi et al. Brain Connectivity, Jul 16 2021. https://doi.org/10.1089/brain.2020.0878

Abstract

Background/Introduction: Sex classification using functional connectivity (FC) from resting-state fMRI (rs-fMRI) has shown promising results. This suggested that sex difference might also be embedded in the blood-oxygen-level-dependent (BOLD) properties like the amplitude of low-frequency fluctuation (ALFF) and the fraction of ALFF (fALFF). This study comprehensively investigates sex differences using a reliable and explainable machine learning (ML) pipeline. Five independent cohorts of resting-state fMRI with over than 5500 samples were used to assess sex classification performance and map the spatial distribution of the important brain regions.

Methods: Five rsfMRI samples were used to extract ALFF and fALFF features from predefined brain parcellations and then were fed into an unbiased and explainable ML pipeline with a wide range of methods. The pipeline comprehensively assessed unbiased performance for within-sample and across sample validation. Additionally, the parcellation effect, classifiers selection, scanning length, spatial distribution, reproducibility, and feature importance were analyzed and evaluated thoroughly in the study.

Results: The results demonstrated high sex classification accuracies from healthy adults (area under the curve (AUC) > 0.89) while degrading for non-healthy subjects. Sex classification showed moderate to good intraclass correlation coefficient (ICC) based on parcellation. Linear classifiers outperform non-linear classifiers. Sex differences could be detected even with a short rs-fMRI scan (e.g., 2 minutes). The spatial distribution of important features overlaps with previous results from Studies.

Discussion: Sex differences are consistent in rs-fMRI and should be considered seriously in any study design, analysis, or interpretation. Features that discriminate males and females were found to be distributed across several different brain regions, suggesting a complex mosaic for sex differences in resting-state fMRI.

The evidence is consistent with the possibility that urgent care centers—which are increasingly owned by or contract with hospital systems—induce greater spending on hospital care

Do Urgent Care Centers Reduce Medicare Spending? Janet Currie, Anastasia Karpova & Dan Zeltzer. NBER Working Paper 29047. Jul 2021. DOI 10.3386/w29047

Abstract: We examine the impact of the opening of a new urgent care center (UCC) on health care costs and the utilization of care among nearby Medicare beneficiaries. We focus on 2006–2016, a period of rapid UCC expansion. We find that total Medicare spending rises when residents of a zip code are first served by a UCC, relative to spending in yet-to-be-served zip codes, while mortality remains flat. We explore mechanisms by looking at categories of spending and by examining utilization. Increases in inpatient visits are the largest contributor to the overall increase in spending, rising by 6.65 percent within six years after UCC entry. The number of emergency room visits that result in a hospital admission also increases by 3.7 percent. In contrast, there is no change in the number of ER visits that do not result in admission to hospital, in visits to physicians outside a UCC, or in imaging and tests. Overall, these results provide little evidence that UCCs replace costly ER visits or that they crowd out visits to patients' regular doctors. Instead, the evidence is consistent with the possibility that UCCs—which are increasingly owned by or contract with hospital systems—induce greater spending on hospital care.

The Decline of Drudgery and the Paradox of Hard Work

The Decline of Drudgery and the Paradox of Hard Work. Brendan Epstein & Miles S. Kimball. NBER Working Paper, 29041, July 2021. DOI 10.3386/w29041

Abstract: We develop a theory that focuses on the general equilibrium and long-run macroeconomic consequences of trends in job utility—the process benefits and costs of work. Given secular increases in job utility, work hours per population can remain approximately constant over time even if the income effect of higher wages on labor supply exceeds the substitution effect. In addition, secular improvements in job utility can be substantial relative to welfare gains from ordinary technological progress. These two implications are connected by an equation flowing from optimal hours choices: improvements in job utility that have a significant effect on labor supply tend to have large welfare effects.

Persuading Investors: We show persuasion delivery works mainly through leading investors to form inaccurate beliefs

Persuading Investors: A Video-Based Study. Allen Hu & Song Ma. NBER Working Paper 29048, July 2021. DOI 10.3386/w29048

Abstract: Persuasive communication functions not only through content but also delivery, e.g., facial expression, tone of voice, and diction. This paper examines the persuasiveness of delivery in start-up pitches. Using machine learning (ML) algorithms to process full pitch videos, we quantify persuasion in visual, vocal, and verbal dimensions. Positive (i.e., passionate, warm) pitches increase funding probability. Yet conditional on funding, high-positivity startups underperform. Women are more heavily judged on delivery when evaluating single-gender teams, but they are neglected when co-pitching with men in mixed-gender teams. Using an experiment, we show persuasion delivery works mainly through leading investors to form inaccurate beliefs.

Origins of Values Differences: A Two-Level Analysis of Economic, Climatic and Parasite Stress Explanations

Origins of Values Differences: A Two-Level Analysis of Economic, Climatic and Parasite Stress Explanations in the Value Domain. Ronald Fischer. Cross-Cultural Research, July 12, 2021. https://doi.org/10.1177/10693971211031476

Abstract: What variables are associated with cross-cultural differences in values at the individual level? In this study, the statistical effect of variables associated with ecological demands and available economic and cognitive resources on self-reported values are investigated in two independent samples to test the replicability of effects. Values are operationalized using a 10-item version inspired by Schwartz’ value theory. The effects of national wealth, climatic demands, availability of cool water, and parasite stress at the national level are used to predict value scores of individuals within nations using nationally representative data from all inhabited continents (k = 49 and k = 58; Ns = 64,491 and 81,991). Using mixed-effect models, new insights into individual- and nation-level dynamics in value scores are provided. First, the paper extends previous cultural theories to the individual level by investigating the effects of education and personal income as individual-level resources. Both personal income and education have strong direct effects on value scores. Second, higher education acts as a cognitive resource which turns climatic demands into challenges, effectively unpackaging nation-level theorizing with individual level dynamics. Third, contrary to previous nation-level research, parasite stress was not a significant predictor of individual-level values. Forth, supporting recent theorizing, individuals located in cool water regions reported significantly higher self-transcendence values. Fifth, the effects of wealth on openness values were convergent and reinforcing across levels (higher wealth is associated with more openness values), but operated in opposing directions for self-transcendence values (national wealth is associated with self-transcendent values, individual wealth is associated with self-enhancing values). The current patterns suggest that cultural research needs to pay more attention to individual versus nation-level dynamics and increase replication efforts with independent samples.

Keywords: values, culture, climate-economic theory, parasite stress, wealth, multi-level, cross-cultural differences

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Having disposal income in a wealthy environment potentiates and unleashes an even faster drive toward greater emancipation of individual desires and actions

Across cultures, there are positive emotions that are more permissible to show, like gratitude, interest, and amusement, and other we not as permissible to display (sensory pleasure, feeling moved, and to some degree triumph)

Manokara, Kunalan, Agneta Fischer, and Disa Sauter. 2020. “Display Rules Differ Between Positive Emotions: Not All That Feels Good, Looks Good.” OSF Preprints. April 25. doi:10.31219/osf.io/4uaym

Abstract: People do not always show how they feel; norms often dictate when to display emotions and to whom. Norms about emotional expressions – known as display rules – are weaker for happiness than for negative emotions, suggesting that expressing positive emotions is generally seen as acceptable. But does it follow that all positive emotions can always be shown to everyone? To answer this question, we mapped out context-specific display rules for eight positive emotions: gratitude, admiration, interest, relief, amusement, feeling moved, sensory pleasure, and triumph. In four studies with participants from five countries (n = 1,181), two consistent findings emerged. First, display rules differed between positive emotions. Weaker display rules were found for gratitude, interest, and amusement, while stronger display rules were found for sensory pleasure, feeling moved, and to some degree triumph. Second, contextual features – such as expresser location and perceiver relationship – both substantially influenced display rules for positive emotions, with perceiver relationship having a greater impact on display rules than expresser location. Our findings demonstrate that not all positive emotions are equally acceptable to express, and highlight the central role of context in influencing display rules even for emotions that feel good. In so doing, we provide the first map of expression norms for specific positive emotions.

Does Transportation Mean Transplantation? Impact of New Airline Routes on Sharing of Cadaveric Kidneys

Does Transportation Mean Transplantation? Impact of New Airline Routes on Sharing of Cadaveric Kidneys. Guihua Wang , Ronghuo Zheng , Tinglong Dai. Management Science, Jul 9 2021. https://doi.org/10.1287/mnsc.2021.4103

Abstract: Every year, nearly 5,000 patients die while waiting for kidney transplants, and yet an estimated 3,500 procured kidneys are discarded. Such a polarized coexistence of dire scarcity and massive wastefulness has been mainly driven by insufficient pooling of cadaveric kidneys across geographic regions. Although numerous policy initiatives are aimed at broadening organ pooling, they rarely account for a key friction—efficient airline transportation, ideally direct flights, is necessary for long-distance sharing, because of the time-sensitive nature of kidney transplantation. Conceivably, transplant centers may be reluctant to accept kidney offers from far-off locations without direct flights. In this paper, we estimate the effect of the introduction of new airline routes on broader kidney sharing. By merging the U.S. airline transportation and kidney transplantation data sets, we create a unique sample tracking (1) the evolution of airline routes connecting all the U.S. airports and (2) kidney transplants between donors and recipients connected by these airports. We estimate the introduction of a new airline route increases the number of shared kidneys by 7.3%. We also find a net increase in the total number of kidney transplants and a decrease in the organ discard rate with the introduction of new routes. Notably, the posttransplant survival rate remains largely unchanged, although average travel distance increases after the introduction of new airline routes. Our results are robust to alternative empirical specifications and have important implications for improving access to the U.S. organ transplantation system.

Theoretically, wealthier people should buy less insurance & should self-insure through saving instead, as insurance entails monitoring costs; differential background risk by wealth levels & differential exposure to legal risk help explain the puzzle

Wealth and Insurance Choices: Evidence from US Households. Michael Gropper, Camelia M. Kuhnen. Jul 2021. http://public.kenan-flagler.unc.edu/faculty/kuhnenc/RESEARCH/gropper_kuhnen.pdf

Abstract: Theoretically, wealthier people should buy less insurance, and should self-insure through saving instead, as insurance entails monitoring costs. Here, we use administrative data for 63,000 individuals and, contrary to theory, find that the wealthier have better life and property insurance coverage. Wealth-related differences in background risk, legal risk, liquidity constraints, financial literacy, and pricing explain only a small fraction of the positive wealth-insurance correlation. This puzzling correlation persists in individual fixed-effects models estimated using 2,500,000 person-month observations. The fact that the less wealthy have less coverage, though intuitively they benefit more from insurance, might increase financial health disparities among households.

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From a seminar by Ms Kuhnen, Jun 2021. Wealth and Insurance Choices: Evidence from US Households – Tinbergen.nl

Abstract: Most individuals purchase insurance products, yet empirically we know little about this aspect of the financial portfolios of households. Theoretically, one of the most important factors that should influence insurance purchases is wealth. Specifically, classic economic models posit that wealthier individuals will purchase less insurance compared to their less well-off peers and will prefer to self-insure instead, as it is cheaper to do so given that insurance products come with monitoring and other costs. In the context of life and property insurance, there is scarce empirical evidence as to how wealth relates to insurance choices, and existing evidence is mainly based on survey data. Here we use administrative data covering more than 60,000 individuals to examine the relation between wealth and insurance coverage. We document that the prediction of classic theories of insurance choices is contradicted in the data. Specifically, we find that wealthier individuals have more extensive coverage in terms of life insurance, homeowners insurance, and other property-related insurance. We investigate which characteristics of individuals or insurance markets lead to this empirical pattern, to assess which features need to be accounted for by future theoretical models of households' insurance choices. Differential background risk by wealth levels, as well as differential exposure to legal risk help account for the puzzling relation we document between wealth and insurance coverage.

While siblings can be close allies, they can also be significant competitors; greater levels of conflict were reported by sisters, those closer in age, those who have co-resided longer, & full-siblings compared to half-siblings

Good Friends, Better Enemies? The Effects of Sibling Sex, Co-Residence, and Relatedness on Sibling Conflict and Cooperation. Catherine A. Salmon & Jessica A. Hehman. Evolutionary Psychological Science, Jul 19 2021. https://rd.springer.com/article/10.1007/s40806-021-00292-y

Abstract: While siblings can be close allies, they can also be significant competitors. They are also family members that are typically with us for most of our lives. Research has raised questions about the factors shaping sibling relationships, and an adaptationist perspective would predict a role for a number of factors including sex, genetic relatedness, and childhood co-residence. Recent work has highlighted sex differences with regard to conflict and emotional closeness, greater conflict among full-siblings than half-siblings, and a role for co-residence in increasing sibling altruism. This study examines levels of both sibling conflict and sibling cooperation as a function of respondent sex, sex of sibling, birth interval (or absolute age difference), co-residence, and relatedness. Results indicate that sibling conflict and cooperation may not be shaped by the same set of factors. Sibling conflict was predicted by own sex, sex of sibling, birth interval, duration of co-residence, and the degree of relatedness. Greater levels of conflict were reported by sisters, those closer in age, those who have co-resided longer, and full-siblings compared to half-siblings. However, sibling prosocialness was only predicted by sex and relatedness with females and full siblings reporting greater levels of sibling prosocialness. More research investigating patterns of conflict and cooperation within families using more ecologically valid cues are necessary to determine whether the two are operating under the same mechanism, sensitive to the same cues, or are, indeed, operating under different mechanisms.

Understanding the onset of hot streaks across artistic, cultural, and scientific careers

Understanding the onset of hot streaks across artistic, cultural, and scientific careers. Lu Liu, Nima Dehmamy, Jillian Chown, C. Lee Giles, Dashun Wang. arXiv Mar 2021. https://arxiv.org/abs/2103.01256

Hot streaks dominate the main impact of creative careers. Despite their ubiquitous nature across a wide range of creative domains, it remains unclear if there is any regularity underlying the beginning of hot streaks. Here, we develop computational methods using deep learning and network science and apply them to novel, large-scale datasets tracing the career outputs of artists, film directors, and scientists, allowing us to build high-dimensional representations of the artworks, films, and scientific publications they produce. By examining individuals' career trajectories within the underlying creative space, we find that across all three domains, individuals tend to explore diverse styles or topics before their hot streak, but become notably more focused in what they work on after the hot streak begins. Crucially, we find that hot streaks are associated with neither exploration nor exploitation behavior in isolation, but a particular sequence of exploration followed by exploitation, where the transition from exploration to exploitation closely traces the onset of a hot streak. Overall, these results unveil among the first identifiable regularity underlying the onset of hot streaks, which appears universal across diverse creative domains, suggesting that a sequential view of creative strategies that balances experimentation and implementation may be particularly powerful for producing long-lasting contributions, which may have broad implications for identifying and nurturing creative talents.

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Individual behavior At the individual level, the ‘essential tension’ hypothesis by Thomas Kuhn [60] illustrates the choice between exploiting existing ideas and exploring newyet risky opportunities. The sociology of science offers severalfundamentaltheoretical discussions [61,62]. Morerecently, empiricalanlaysishasbeenconductedtoquantitatively understand the ‘essential tension’ hypothesis. For example, Foster et al. [53] analyzed millions of abstracts from MEDLINE, and identified topics from the clusters on the chemical networkto trace the researchstrategy ofbiomedical researchers [63]. In addition,thePACS code in American Physical Society (APS) dataset has also been widely used to quantify exploration and exploitation for scientific careers [18, 52, 64].

Researchers have also studied various environmental, social and individualfactors that may influence one’s choice between exploration and exploitation [48]. Environmentalfactors include resource status of a local position [49, 65], cost and reward of exploration and exploitation [65, 66], available information on different options [67], and more. Discussions centered around how long individuals should stay in the exploitation/exploration phase and when to change their behaviors under different environmental settings. For example, the probability of exploration increases when the resource is depleted, when the cost of exploration decreases, or when individuals are uncertain about the options. The social factors are widely discussed in social learning strategies and collective intelligence [68–72], ranging fromtask complexity [73], to past success and failure [71, 73]tonetwork structures [74, 75]. Individuals can update their strategies like exploration, exploitation or copying others to increase theirpayoffsunderdifferent settings.Individual factors such as personalities [76], cognitive capacity [77], and aspiration level[78], also influence one’s propensity to explore or exploit.

In the literature of strategic management and organization theory, scholars have examined exploration and exploitation behaviors ofindividuals and firms, particularly focusing ontheeffects thishasonorganizationaloutcomes. Forexample,Singh&Agrawal[79]found that when scientists begin working within a new organization, the organization increases their use of the new recruit’s prior work and that the majority of the effect is due to the employee’s own exploitation of their prior work. Groysberg & Lee [80] found that when star security analysts were hired to explore (i.e., to initiate new activities for the organization), they experienced a drop in performance; whereas star security analysts hired to engage in exploitation (i.e., to reinforce the organization’s existing activities) experienced a boost in performance. Other research has looked at the antecedents of individuals’ exploration and exploitation behaviors. For example, Lee & Meyer-Doyle [81] examined how financialincentives shapedthebehavior of salespeopleandfoundthatindividuals engaged in more exploration when performance-based incentives were weakened but this increase wasdriven by the organization’s strongestperformers. Recent study on network oscillation for bankers [82] suggests that switching between exploration and exploitation has positive effects on the employee’s network advantage.

Organization learning, design and adaptation

At the macro level, another important line of research examines exploration and exploitation in the context of organization learning, organization design, and organizational adaptation [58]. This line of work builds on the canonical work by March [57], and suggests that both exploration and exploitation are critical for an organization’s performance, but they are inherently in tension and that this tension must be actively managed [83]. This tension reflects trade-offs between short vs. long-termperformance and stability vs. adaptability [57, 84–87]. Debates in this literature center onseveralfundamental questions: Do exploration and exploitation exist as twoends of a continuum (and so cannot coexist at the same time) or are they orthogonal discrete choices? Can organizations find a balance between exploration and exploitation activities or should they specialize in one or the other? It also explores the antecedents to organizations’decisions topursue exploration or exploitation [59, 88], examining environmental factors (e.g., exogenous shocks, competitive dynamics) as well as organizational factors (e.g., culture, resources, capabilities)thatinfluence that choice. This literaturealsouses the notion of organizational ambidexterity to describe the ability to do both exploration and exploitation simultaneously [89]. Finally, this research examines the performance implications for organizations of adopting different approaches to balancing this enduring trade-off between exploration and exploitation [90]. This line of research is performed using multiple different methodologies including empirical studies using quantitative and qualitative data from organizations, theoretical models [91], and agent-based simulations [59, 92, 93].

Idea formation

At a more micro level, the discussion of exploration and exploitation is particularly relevantto studies on idea formation and innovation process [94–96], which models themechanismofinnovationas randomwalksonthenetworkofideas/landscapeof solutions. In this setting, exploration and exploitation is usually defined as creating new path or reproducing existing ideas. For example, Iacopini et al [94] models the cognitive growthofknowledgeinscienceforover20yearsandvalidateprocesswithconceptnetworks curated from WoS abstracts. Studies have shown that both existing knowledge and novel combinations are essential for producing high-impact scientific papers [97]. The discussion goes beyond science to innovation and technology as well. For example, Youn et al.[98] analyzed technology codes used byUSPTO to quantify innovation strategy,finding a constant rate of exploration and exploitation in patent records. Overall, our results contribute to these three lines of literature in several ways. First, by documenting the relationship between exploration, exploitation and career hot streaks, our results demonstrate broader relevance ofthe concepts of exploration and exploitation, extendingbeyond existing individual ororganizational settings to theunderstanding ofhot streaks and individual creative careers. At root, our results suggest the important role of both exploration and exploitation in individual careers. Curiously, across a wide range of creative domains, a major turning point for individual careers appears most closely linked withneitherexplorationnorexploitationbehaviorinisolation,butratherwiththeparticular sequence of exploration followed by exploitation, which highlights our second contribution. Indeed, extantliteraturehasdocumentedthefundamental roleofexplorationandexploitation in creativity. Yet as creative behaviors, they have traditionally been considered either in isolation [53, 60] or in combination [58, 99] but rarely in succession. Our results suggest a sequential view of creative strategies that balance experimentation and implementation may be particularly powerful for producing long-lasting contributions.

From 2020... Less Sex, but More Sexual Diversity: Changes in Sexual Behavior during the COVID-19 Coronavirus Pandemic

From 2020... Less Sex, but More Sexual Diversity: Changes in Sexual Behavior during the COVID-19 Coronavirus Pandemic. Justin J. Lehmiller, Justin R. Garcia, Amanda N. Gesselman & Kristen P. Mark. Leisure Sciences Volume 43, 2021 - Issue 1-2, Pages 295-304. Jun 26 2020. https://doi.org/10.1080/01490400.2020.1774016

Abstract: Recreational sex is a popular form of leisure that has been redefined by the COVID-19 (coronavirus) pandemic. “Social distancing” rules have imposed limits on sex for leisure while also creating new opportunities. We discuss results from an online survey of 1,559 adults who were asked about the pandemic’s impact on their intimate lives. While nearly half of the sample reported a decline in their sex life, one in five participants reported expanding their sexual repertoire by incorporating new activities. Common additions included sexting, trying new sexual positions, and sharing sexual fantasies. Being younger, living alone, and feeling stressed and lonely were linked to trying new things. Participants making new additions were three times more likely to report improvements in their sex life. Even in the face of drastic changes to daily life, many adults are adapting their sexual lives in creative ways.

Keywords: coronavirusCOVID-19sexual behaviorsexual noveltysocial distancing

Implications

The COVID-19 pandemic is impacting people’s sexual lives. This is evidenced in our initial empirical multinational data on the impact of lockdowns and physical distancing restrictions on people’s intimate lives. These findings are consistent with a smaller simultaneous study demonstrating a decrease in sexual frequency among a sample of young adults in China (Li et al., 2020), but they differ from a report of married people in Southeast Asia who reported unspecified changes in their sexual life but not decreases in sexual frequency (Arafat et al., 2020). Although our sample is not representative and caution is warranted in generalizing broadly, these findings nonetheless make an important and novel contribution to the literature and to our collective understanding of the influence of the COVID-19 pandemic and physical distancing on sociality, leisure, and sex.

There are several important implications of this work. While a majority of our participants reported no new additions to their sex lives, a substantial minority did. This finding adds much-needed complexity and nuance to the popular media narrative surrounding sex during this unusual time. It is clear that many people’s sex lives are undergoing a revolution of sorts, in which they are expanding their sexual repertoires; however, this does not appear to be as widespread and as laser-focused on SexTech as the media suggest. In fact, the single most common new addition did not require any technology at all: trying a new sexual position. This suggests that the changes going on in people’s intimate lives are broader in scope than assumed.

We also found that more participants said their sex lives declined rather than improved—and while incorporating new activities into one’s sex life was linked to improvements, new additions did not eliminate declines. Generally, only partnered activities were linked to improvements, with few technology-based activities showing any association. The new additions most strongly correlated with sex life improvement were trying new positions, acting on fantasies, engaging in BDSM, and giving massages. By contrast, the most common technology-based additions (sexting, sending nudes) were unrelated to sexual improvements. This suggests that while incorporating more technology into one’s sex life was common, it did not appear to have been as gratifying as in-person activities.

Consequently, we caution against premature claims that the COVID-19 pandemic will necessarily usher in widespread SexTech use, recreationally and otherwise. It is possible that recent uptake of SexTech is a temporary coping strategy and that once the pandemic subsides, technology usage may decrease in favor of in-person, partnered interactions.

By understanding factors associated with sexual improvements during this unprecedented time, we are also able to identify factors that might help people better navigate their intimate lives and safely pursue leisure activities during future emergency situations. For example, encouraging more novel sexual pursuits with a partner may be a helpful and therapeutic strategy for persons in relationships, particularly those feeling stressed or lonely. Likewise, the fact that SexTech was largely unrelated to sexual improvements points to important areas for future research and education. Are there ways of making these interactions more satisfying? Can SexTech education make usage more fulfilling?

The widespread social restrictions put in place during the COVID-19 pandemic appear to have significantly disrupted sexual routines and the overall quality of people’s sex lives. However, even in the face of these drastic changes, it is apparent that many adults are finding creative ways to adapt their sexual lives, including in the pursuit of sex for leisure.