Seeing storms behind the clouds: Biases in the attribution of anger

Anger-prone individuals are volatile and frequently dangerous. Accordingly, inferring the presence of this personality trait in others was important in ancestral human populations. This inference, made under uncertainty, can result in two types of errors: underestimation or overestimation of trait anger. Averaged over evolutionary time, underestimation will have been the more costly error, as the fitness decrements resulting from physical harm or death due to insufficient vigilance are greater than those resulting from lost social opportunities due to excessive caution. We therefore hypothesized that selection has favored an upwards bias in the estimation of others' trait anger relative to estimations of other traits not characterized by such an error asymmetry. Moreover, we hypothesized that additional attributes that i) make the actor more dangerous, or ii) make the observer more vulnerable increase the error asymmetry with regard to inferring anger-proneness, and should therefore correspondingly increase this overestimation bias. In Study 1 (N = 161), a fictitious individual portrayed in a vignette was judged to have higher trait anger than trait disgust, and trait anger ratings were more responsive than trait disgust ratings to behavioral cues of emotionality. In Study 2 (N = 335), participants viewed images of angry or fearful faces. The interaction of factors indicating target's formidability (male sex), target's intent to harm (direct gaze), and perceiver's vulnerability (female sex or high belief in a dangerous world) increased ratings of the target's trait anger but not trait fear.     

EVOLVABILITY OF INDIVIDUAL TRAITS IN A MULTIVARIATE CONTEXT: PARTITIONING THE ADDITIVE GENETIC VARIANCE INTO COMMON AND SPECIFIC COMPONENTS

Genetic covariation among multiple traits will bias the direction of evolution. Although a trait's phenotypic context is crucial for understanding evolutionary constraints, the evolutionary potential of one (focal) trait, rather than the whole phenotype, is often of interest. The extent to which a focal trait can evolve independently depends on how much of the genetic variance in that trait is unique. Here, we present a hypothesis‐testing framework for estimating the genetic variance in a focal trait that is independent of variance in other traits. We illustrate our analytical approach using two Drosophila bunnanda trait sets: a contact pheromone system comprised of cuticular hydrocarbons (CHCs), and wing shape, characterized by relative warps of vein position coordinates. Only 9% of the additive genetic variation in CHCs was trait specific, suggesting individual traits are unlikely to evolve independently. In contrast, most (72%) of the additive genetic variance in wing shape was trait specific, suggesting relative warp representations of wing shape could evolve independently. The identification of genetic variance in focal traits that is independent of other traits provides a way of studying the evolvability of individual traits within the broader context of the multivariate phenotype.     

The emotion–valuation constellation: Multiple emotions are governed by a common grammar of social valuation

Social emotions are hypothesized to be adaptations designed by selection to solve adaptive problems pertaining to social valuation—the disposition to attend to, associate with, and aid a target individual based on her probable contributions to the fitness of the valuer. To steer between effectiveness and economy, social emotions need to activate in precise proportion to the local evaluations of the various acts and characteristics that dictate the social value of self and others. Supporting this hypothesis, experiments conducted in the United States and India indicate that five different social emotions all track a common set of valuations. The extent to which people value each of 25 positive characteristics in others predicts the intensities of: pride (if you had those characteristics), anger (if someone failed to acknowledge that you have those characteristics), gratitude (if someone convinced others that you have those characteristics), guilt (if you harmed someone who has those characteristics), and sadness (if someone died who had those characteristics). The five emotions track local valuations (mean r = +.72) and even foreign valuations (mean r = +.70). In addition, cultural differences in emotion are patterned: They follow cultural differences in valuation. These findings suggest that multiple social emotions are governed (in part) by a common architecture of social valuation, that the valuation architecture operates with a substantial degree of universality in its content, and that a unified theoretical framework may explain cross-cultural invariances and cultural differences in emotion.     

Darwin and sexual selection: One hundred years of misunderstanding

Darwin's book on the Descent of Man and Selection in Relation to Sex (1871) is often viewed as the continuation of TheOrigin of Species published 12 years earlier (1859), both because of the implicit parallelism between natural selection and sexual selection, and because Darwin himself presents the book as developing a subject (man) which he intentionally omitted in the Origin. But the Descent can also be viewed as the continuation of his book on Variation published three years earlier (1868). Firstly because Darwin's hypothesis of pangenesis links the selection process to the origin of variation through use and disuse, an idea underlying his speculations on the origin of moral sense in humans. Second because like the action of the horticulturist on his domestic crops, sexual selection exerted by one sex on the other sex can develop fancy traits that are not easily accounted for by their utility to the selected organism itself, such as artistic taste, pride, courage, and the morphological differences between human populations. These traits are difficult to reconcile with pangenesis. They add up to other contradictions of the book possibly resulting from Darwin's erroneous inference about the mechanism of inheritance, like those on the determination of sex-ratio, or the confusion between individual adaptation and the advantage to the species. These inconsistencies inaugurate a weakening of the Darwinian message, which will last 50 years after his death. They contributed to the neglect of sexual selection for a century. Darwin however maintained a logical distinction between evolutionary mechanisms and hereditary mechanisms, and an epistemological distinction between evolutionary theory and Pangenesis hypothesis. In the modern context of Mendelian genetics, Darwin's sexual selection retrospectively appears as luminous an idea in its pure principle as natural selection, even though the mechanisms governing the evolution of sexual choice in animals remain largely unresolved.     

Multicomponent shell traits are consistent with an individual recognition function of the appearance of common murre (Uria aalge) eggs: A biological replication study

In dense breeding colonies, and despite having no nest structure, common murres (or guillemots: Uria aalge) are still able to identify their own eggs. Each female murre''s egg is thought to be recognized individually by the shell''s avian‐perceivable traits. This is because the eggshells’ visible traits conform to expectations of the identity‐signaling hypothesis in that they show both high intraindividual repeatability and high interindividual variability. Identity signaling also predicts a lack of correlation between each of the putative multicomponent recognition traits, yielding no significant relationships between those eggshell traits that are generated by mutually exclusive physiological factors. Using a multivariate analysis across eggshell size and shape, avian‐perceivable background coloration, spot (maculation) shape, and spot density, we detected no unexpected statistical correlations between Icelandic common murre egg traits lacking known physiological or mathematical relationships with one another. These results biologically replicate the conclusions of a recent eggshell trait study of Canadian common murres using similar methodology. We also demonstrate the use of static correlations to infer identity signaling function without direct behavioral observations, which in turn may also be applied to rare or extinct species and provide valuable insight into otherwise unknown communicative and behavioral functions.     

Heterozygosity-based assortative mating in blue tits (Cyanistes caeruleus): implications for the evolution of mate choice

The general hypothesis of mate choice based on non-additive genetic traits suggests that individuals would gain important benefits by choosing genetically dissimilar mates (compatible mate hypothesis) and/or more heterozygous mates (heterozygous mate hypothesis). In this study, we test these hypotheses in a socially monogamous bird, the blue tit (Cyanistes caeruleus). We found no evidence for a relatedness-based mating pattern, but heterozygosity was positively correlated between social mates, suggesting that blue tits may base their mating preferences on partner''s heterozygosity. We found evidence that the observed heterozygosity-based assortative mating could be maintained by both direct and indirect benefits. Heterozygosity reflected individual quality in both sexes: egg production and quality increased with female heterozygosity while more heterozygous males showed higher feeding rates during the brood-rearing period. Further, estimated offspring heterozygosity correlated with both paternal and maternal heterozygosity, suggesting that mating with heterozygous individuals can increase offspring genetic quality. Finally, plumage crown coloration was associated with male heterozygosity, and this could explain unanimous mate preferences for highly heterozygous and more ornamented individuals. Overall, this study suggests that non-additive genetic traits may play an important role in the evolution of mating preferences and offers empirical support to the resolution of the lek paradox from the perspective of the heterozygous mate hypothesis.     

Value computation in humans

Things afford positive, neutral, or negative long-run effects on the replicative probability of the focal individual's genes. At the most general level, values are internal estimates of those effects. Value information steers physiology and behavior in the right direction: approach apple, avoid lion. Thus, value computation is of paramount biological importance. Task analysis suggests there are many prerequisites for valuing things aptly. Here, I focus on two: the need to compute value accurately, and the need to properly feed and integrate value information into the various systems that use value information (e.g., emotion systems). For example, the subjective food value imputed to an apple needs to reflect the nutrient content of the apple (accuracy); the intensity of gratitude aroused if someone gave you an apple needs to reflect the food value imputed to the apple (integration). Here, I evaluate these hypotheses with two preregistered studies. Consistent with the integration hypothesis, there are close correspondences between (i) the food values that participants impute to each of 40 food items (Study 1; goods) and (ii) the social values and the social emotions (including: gratitude, anger, shame, and pride) that result when those food items occur as constituents of broader social events. Similar correspondences are observed when participants evaluate each of 28 diseases and injuries (Study 2; bads). Consistent with the accuracy hypothesis, exploratory analyses indicate that the food values, the social values, and the social emotions elicited by the food items all track the nutrient content of those food items. Valuation is inherently a computational process. For this reason, a computational–functionalist perspective is distinctively suited to spur progress in our understanding of human values.     

TRAIT COMPENSATION AND SEX‐SPECIFIC AGING OF PERFORMANCE IN MALE AND FEMALE PROFESSIONAL BASKETBALL PLAYERS

Phenotypic traits are often influenced by dynamic resource allocation trade‐offs which, when occurring over the course of individual lifespan, may manifest as trait aging. Although aging is studied for a variety of traits that are closely tied to reproduction or reproductive effort, the aging of multiple traits related to fitness in other ways are less well understood. We took advantage of almost 30 years of data on human whole‐organism performance in the National Basketball Association (USA) to examine trends of aging in performance traits associated with scoring. Given that patterns of aging differ between sexes in other animal species, we also analyzed a smaller dataset on players in the Women's National Basketball Association to test for potential sex differences in the aging of comparable traits. We tested the hypothesis that age‐related changes in a specific aspect of overall performance can be compensated for by elevated expression of another, related aspect. Our analyses suggest that the aging of performance traits used in basketball is generally characterized by senescence in males, whereas age‐related changes in basketball performance are less evident in females. Our data also indicate a different rate of senescence of different performance traits associated with scoring over a male's lifetime.     

A multivariate approach to human mate preferences

Human mate choice is complicated, with various individual differences and contextual factors influencing preferences for numerous traits. However, focused studies on human mate choice often do not capture this multivariate complexity. Here, we consider multiple factors simultaneously to demonstrate the advantages of a multivariate approach to human mate preferences. Participants (N = 689) rated the attractiveness of opposite-sex online dating profiles that were independently manipulated on facial attractiveness, perceived facial masculinity/femininity, and intelligence. Participants were also randomly instructed to either consider short- or long-term relationships. Using fitness surfaces analyses, we assess the linear and nonlinear effects and interactions of the profiles' facial attractiveness, perceived facial masculinity/femininity, and perceived intelligence on participants' attractiveness ratings. Using hierarchical linear modeling, we were also able to consider the independent contribution of participants' individual differences on their revealed preferences for the manipulated traits. These individual differences included participants' age, socioeconomic status, education, disgust (moral, sexual, and pathogen), sociosexual orientation, personality variables, masculinity, and mate value. Together, our results illuminate various previously undetectable phenomena, including nonlinear preference functions and interactions with individual differences. More broadly, the study illustrates the value of considering both individual variation and population-level measures when addressing questions of sexual selection, and demonstrates the utility of multivariate approaches to complement focused studies.     

INTERPRETING REJECTIONS OF THE BENEFICIAL ACCLIMATION HYPOTHESIS: WHEN IS PHYSIOLOGICAL PLASTICITY ADAPTIVE?

Abstract.— Although many studies testing the beneficial acclimation hypothesis have rejected it, what these rejections imply about the adaptive value of physiological change remains unclear. Uncertainty arises because the hypothesis focuses on the relative performance of organisms exposed to one environment versus another, whereas the raw material available to evolution is variation in acclimation responses of individual traits. This mismatch is problematic when organisms are exposed to poor environments. In poor environments, the adaptive or maladaptive value of changes in individual traits may be obscured by long-term decrements in organismal condition. A better match between the evolutionary pressures shaping acclimation and the tests used to examine them can be achieved by focusing on the fitness consequences of acclimation changes in individual traits.     

Self-Relevance Appraisal Influences Facial Reactions to Emotional Body Expressions

People display facial reactions when exposed to others'' emotional expressions, but exactly what mechanism mediates these facial reactions remains a debated issue. In this study, we manipulated two critical perceptual features that contribute to determining the significance of others'' emotional expressions: the direction of attention (toward or away from the observer) and the intensity of the emotional display. Electromyographic activity over the corrugator muscle was recorded while participants observed videos of neutral to angry body expressions. Self-directed bodies induced greater corrugator activity than other-directed bodies; additionally corrugator activity was only influenced by the intensity of anger expresssed by self-directed bodies. These data support the hypothesis that rapid facial reactions are the outcome of self-relevant emotional processing.     

Morphological and genetic predictors of parental care in the North American barn swallow Hirundo rustica erythrogaster

Sexually dimorphic traits often signal the fitness benefits an individual can provide to potential mates. In species with altricial young, these signals may also predict the level of parental care an individual is expected to provide to shared offspring. In this study, we tested three hypotheses that traditionally relate sexually dimorphic traits to parental care in two populations of North American barn swallows Hirundo rustica erythrogaster. The good parent hypothesis predicts a positive relationship between an individual's ornamentation and his or her care whereas the differential allocation (more care given by individuals when paired to high quality mates) and reproductive compensation (more care given by individuals when paired to low quality mates) hypotheses predict that an individual's level of parental investment is relative to the quality of their mate. Male and female North American barn swallows have colorful ventral feathers and elongated tail streamers, but there is evidence that ventral color, not tail streamer length, predicts measures of seasonal reproductive success. Accounting for the positive correlation between within‐pair feeding rates and other potentially confounding variables in all of our models, we found no support for the good parent hypothesis because in both males and females, traits shown to be under sexual selection did not predict feeding rates in either sex. However, our data reveal that male coloration, and not streamer length, predicted a female's provisioning rate to shared offspring (females fed more when paired with darker individuals) in two separate populations, supporting the differential allocation, but not the reproductive compensation hypothesis. Because genetic traits have also been shown to affect parental investment, we evaluated this variable as well and found that a male's paternity did not have significant effects on either male or female feeding rates. Overall, our results suggest that females do not pair with darker males in order to gain direct benefits in terms of his expected levels of parental care to shared offspring, but do themselves invest greater levels of care when paired to darker males. Further, our results are consistent with previous studies which suggest that ventral feather color, not streamer length, is a target of sexual selection in North American populations of barn swallow because females invested more in their offspring when paired to darker mates.     

Observational evidence of herbivore‐specific associational effects between neighboring conspecifics in natural,dimorphic populations of Datura wrightii

Associational effects—in which the vulnerability of a plant to herbivores is influenced by its neighbors—have been widely implicated in mediating plant–herbivore interactions. Studies of associational effects typically focus on interspecific interactions or pest–crop dynamics. However, associational effects may also be important for species with intraspecific variation in defensive traits. In this study, we observed hundreds of Datura wrightii—which exhibits dimorphism in its trichome phenotype—from over 30 dimorphic populations across California. Our aim was to determine whether a relationship existed between the trichome phenotype of neighboring conspecifics and the likelihood of being damaged by four species of herbivorous insects. We visited plants at three timepoints to assess how these effects vary both within and between growing seasons. We hypothesized that the pattern of associational effects would provide rare morphs (i.e., focal plants that are a different morph than their neighbors) with an advantage in the form of reduced herbivory, thereby contributing to the negative frequency‐dependent selection previously documented in this system. We found the best predictor of herbivory/herbivore presence on focal plants was the phenotype of the focal plant. However, we also found some important neighborhood effects. The total number of plants near a focal individual predicted the likelihood and/or magnitude of herbivory by Tupiochoris notatus, Lema daturaphila, and Manduca sexta. We also found that velvety focal plants with primarily sticky neighbors are more susceptible to infestation by Tupiochoris notatus and Lema daturaphila. This does not align with the hypothesis that associational effects at the near‐neighbor scale contribute to a rare‐morph advantage in this system. Overall, the results of our study show that the number and trichome‐morph composition of neighboring conspecifics impact interactions between D. wrightii and insect herbivores.     

The relationship between the minor allele content and Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease. The genetic risk factors of AD remain better understood. Using previously published dataset of common single nucleotide polymorphisms (SNPs), we studied the association between the minor allele content (MAC) in an individual and AD. We found that AD patients have higher average MAC values than matched controls. We identified a risk prediction model that could predict 2.19% of AD cases. We also identified 49 genes whose expression levels correlated with both MAC and AD. By pathway and process enrichment analyses, these genes were found in pathways or processes closely related to AD. Our study suggests that AD may be linked with too many genetic variations over a threshold. The method of correlations with both MAC and traits appears to be effective in high efficiency identification of target genes for complex traits.     

The human anger face evolved to enhance cues of strength

Animals typically deploy their morphology during conflict to enhance competitors' assessments of their fighting ability (e.g. bared fangs, piloerection, dewlap inflation). Recent research has shown that humans assess others' fighting ability by monitoring cues of strength, and that the face itself contains such cues. We propose that the muscle movements that constitute the human facial expression of anger were selected because they increased others' assessments of the angry individual's strength, thereby increasing bargaining power. This runs contrary to the traditional theory that the anger face is an arbitrary set of features that evolved simply to signal aggressive intent. To test between these theories, the seven key muscle movements constituting the anger face were systematically manipulated one by one and in the absence of the others. Raters assessed faces containing any one of these muscle movements as physically stronger, supporting the hypothesis that the anger face evolved to enhance cues of strength.     

Hosts of avian brood parasites have evolved egg signatures with elevated information content

Hosts of brood-parasitic birds must distinguish their own eggs from parasitic mimics, or pay the cost of mistakenly raising a foreign chick. Egg discrimination is easier when different host females of the same species each lay visually distinctive eggs (egg ‘signatures’), which helps to foil mimicry by parasites. Here, we ask whether brood parasitism is associated with lower levels of correlation between different egg traits in hosts, making individual host signatures more distinctive and informative. We used entropy as an index of the potential information content encoded by nine aspects of colour, pattern and luminance of eggs of different species in two African bird families (Cisticolidae parasitized by cuckoo finches Anomalospiza imberbis, and Ploceidae by diederik cuckoos Chrysococcyx caprius). Parasitized species showed consistently higher entropy in egg traits than did related, unparasitized species. Decomposing entropy into two variation components revealed that this was mainly driven by parasitized species having lower levels of correlation between different egg traits, rather than higher overall levels of variation in each individual egg trait. This suggests that irrespective of the constraints that might operate on individual egg traits, hosts can further improve their defensive ‘signatures'' by arranging suites of egg traits into unpredictable combinations.     

The neighborhood matters: effects of neighbor number and sibling (or kin) competition on floral traits in Spergularia marina (Caryophyllaceae)

Abstract.— Effects of abiotic factors on the expression of floral and gender traits have been well documented in wild plant species; by contrast, little is known of the effect(s) on an individual's floral phenotype of the genetic composition of its neighboring conspecifics. Here we report the results of a greenhouse experiment conducted to detect the effects of genetic attributes of an individual's local environment on the expression of floral traits in the selfing annual, Spergularia marina (Caryophyllaceae). First, to test the hypothesis that negative effects of intraspecific competition are stronger when an individual competes with genetically similar individuals than when it competes with unrelated genotypes, we evaluated the effects of the number of nearest-neighbor kin (vs. unrelated individuals) on floral traits. Plants adjacent to two kin produced significantly fewer stamens per flower than plants adjacent to one or no siblings, indicating that kin competition reduced allocation to male function. Second, to test the hypothesis that the genetic diversity of a neighborhood influences the phenotype of a focal plant, we determined whether the number of maternal families represented among an individual's nearest neighbors influences its phenotype. The number of maternal families surrounding a focal plant did not affect floral trait expression. These results suggest that in S. marina , male function is more sensitive than female function to the genetic environment and that as an individual's genetic similarity to its neighbors increases, so do the negative effects of competition for limited resources.     

Understanding Others' Regret: A fMRI Study

Previous studies showed that the understanding of others'' basic emotional experiences is based on a “resonant” mechanism, i.e., on the reactivation, in the observer''s brain, of the cerebral areas associated with those experiences. The present study aimed to investigate whether the same neural mechanism is activated both when experiencing and attending complex, cognitively-generated, emotions. A gambling task and functional-Magnetic-Resonance-Imaging (fMRI) were used to test this hypothesis using regret, the negative cognitively-based emotion resulting from an unfavorable counterfactual comparison between the outcomes of chosen and discarded options. Do the same brain structures that mediate the experience of regret become active in the observation of situations eliciting regret in another individual? Here we show that observing the regretful outcomes of someone else''s choices activates the same regions that are activated during a first-person experience of regret, i.e. the ventromedial prefrontal cortex, anterior cingulate cortex and hippocampus. These results extend the possible role of a mirror-like mechanism beyond basic emotions.     

COMT but not serotonin‐related genes modulates the influence of childhood abuse on anger traits

Anger‐related traits are regulated by genes as well as early environmental factors. Both childhood maltreatment and genes underlie vulnerability to suicidal behaviors, possibly by affecting the constitution of intermediate phenotypes such as anger traits. The aim of this study was to test the interaction between nine candidate genes and childhood maltreatment in modulating anger‐related traits in 875 adult suicide attempters. The State‐Trait Anger Expression Inventory and the Childhood Trauma Questionnaire were used to examine anger traits and traumatic childhood experiences, respectively. The functional polymorphism of the catecholamine‐O‐methyl‐transferase (COMT) gene Val158Met significantly modulated the association between sexual abuse and anger‐trait level (P = 0.001). In the presence of sexual abuse, individuals carrying the Val high‐activity allele displayed greater disposition toward anger than individuals homozygous for the Met allele (P = 0.0003). Notably, none of the serotonin‐related genes influenced the effect of childhood abuse on anger traits. The results of the present study suggest that anger‐trait level is influenced by the interaction between childhood abuse and functional polymorphism in the COMT gene. This study was carried out in a population with a high frequency of childhood abuse and a high disposition toward anger, and replication in healthy subjects is needed.     

Investigation of individual heterozygosity correlated to growth traits in Tongshan Black-boned goat

Ten single nucleotide polymorphisms were used for genotyping of 176 Tongshan Black-boned goats, which are Chinese indigenous goat colony for meat production. The average individual heterozygosity was 0.292. To assess the correlations between individual heterozygosity and growth in Tongshan Black-boned goat individuals, and the potential of using individual heterozygosity as an indicator of growth, the data of growth traits, including body weight, height at withers, body length, chest girth and cannon circumference, were collected. Significant correlations were observed between individual heterozygosity and body weight, height at withers, body length, heart girth, cannon circumference (P < 0.05). All the significant regression showed positive slope with R square values ranged from 0.0251 to 0.0368. These data suggests that individual heterozygosity is positively correlated with growth traits in Tongshan Black-boned goat individuals and associative overdominance may affect Tongshan Black-boned goat growth significantly. Therefore it is possible to use individual heterozygosity as an indicator of growth. Our results also provide a strong support to the overdominance hypothesis.