Rowers' high: behavioural synchrony is correlated with elevated pain thresholds

Physical exercise is known to stimulate the release of endorphins, creating a mild sense of euphoria that has rewarding properties. Using pain tolerance (a conventional non-invasive assay for endorphin release), we show that synchronized training in a college rowing crew creates a heightened endorphin surge compared with a similar training regime carried out alone. This heightened effect from synchronized activity may explain the sense of euphoria experienced during other social activities (such as laughter, music-making and dancing) that are involved in social bonding in humans and possibly other vertebrates.     

Why Do People Laugh during Dog–Human Play Interactions?

Given that human laughter has been posited to signal playfulness to dogs, nonserious social incongruity, and positive affect, laughter should occur during incongruous contexts in an affectively positive, nonserious social activity such as dog–human play. A total of 116 laughs in relation to dogs were discerned on videotapes of 46 dog–human play interactions in the US, 23 with familiar and 23 with unfamiliar pairs. Laughter occurred during 61% of interactions, and always expressed positive affect. Contexts in which laughter occurred (in decreasing frequency) were failure of the dog during play, or to play at all or as the person wanted; exaggerated or unexpected engagement by the dog; excretion; unexpected success by the dog in obtaining an object; and, once, threat from the dog. Laughter never induced play, and usually occurred when a dog was not playing. Women laughed more than men, especially for a male audience when playing with their own dog. In all contexts, participants experienced incongruous events; contexts were nonserious, except for the dog's threat, where laughter signaled friendliness. These data are largely consistent with laughter signaling positive affect and awareness of (usually nonserious) social incongruity, and inconsistent with laughter signaling playfulness to dogs.     

The evolution and functions of laughter and humor: a synthetic approach

A number of recent hypotheses have attempted to explain the ultimate evolutionary origins of laughter and humor. However most of these have lacked breadth in their evolutionary frameworks while neglecting the empirical existence of two distinct types of laughter--Duchenne and non-Duchenne--and the implications of this distinction for the evolution of laughter as a signal. Most of these hypotheses have also been proposed in relative isolation of each other and remain disjointed from the relevant empirical literature. Here we attempt to remedy these shortcomings through a synthesis of previous laughter and humor research followed by (i) a reevaluation of this research in light of theory and data from several relevant disciplines, and (ii) the proposal of a synthetic evolutionary framework that takes into account phylogeny and history as well as proximate mechanisms and adaptive significance. We consider laughter to have been a preadaptation that was gradually elaborated and co-opted through both biological and cultural evolution. We hypothesize that Duchenne laughter became fully ritualized in early hominids between 4 and 2 mya as a medium for playful emotional contagion. This mechanism would have coupled the emotions of small hominid groups and promoted resource-building social play during the fleeting periods of safety and satiation that characterized early bipedal life. We further postulate that a generalized class of nonserious social incongruity would have been a reliable indicator of such safe times and thereby came to be a potent distal elicitor of laughter and playful emotion. This class of stimuli had its origins in primate social play and was the foundation for formal human humor. Within this framework, Duchenne laughter and protohumor were well established in the hominid biobehavioral repertoire when more cognitively sophisticated traits evolved in the hominid line between 2 mya and the present. The prior existence of laughter and humor allowed them to be co-opted for numerous novel functions, and it is from this process that non-Duchenne laughter and the "dark side" of laughter emerged. This perspective organizes the diversified forms and functions that characterize laughter and humor today and clarifies when and how laughter and humor evolved during the course of human evolution.     

Impoverished encoding of speaker identity in spontaneous laughter

Our ability to perceive person identity from other human voices has been described as prodigious. However, emerging evidence points to limitations in this skill. In this study, we investigated the recent and striking finding that identity perception from spontaneous laughter - a frequently occurring and important social signal in human vocal communication - is significantly impaired relative to identity perception from volitional (acted) laughter. We report the findings of an experiment in which listeners made speaker discrimination judgements from pairs of volitional and spontaneous laughter samples. The experimental design employed a range of different conditions, designed to disentangle the effects of laughter production mode versus perceptual features on the extraction of speaker identity. We find that the major driving factor of reduced accuracy for spontaneous laughter is not its perceived emotional quality but rather its distinct production mode, which is phylogenetically homologous with other primates. These results suggest that identity-related information is less successfully encoded in spontaneously produced (laughter) vocalisations. We therefore propose that claims for a limitless human capacity to process identity-related information from voices may be linked to the evolution of volitional vocal control and the emergence of articulate speech.     

The watching eyes effect in the Dictator Game: it's not how much you give,it's being seen to give something

In a classic study, Haley and Fessler showed that displaying subtle eye-like stimuli caused participants to behave more generously in the Dictator Game. Since their paper was published, there have been both successful replications and null results reported in the literature. However, it is important to clarify that two logically separable effects were found in their original experiment: watching eyes made the mean donation higher, and also increased the probability of donating something rather than nothing. Here, we report a replication study with 118 participants, in which we found that watching eyes significantly increased the probability of donating something, but did not increase the mean donation. Results did not depend on the sex of the participants or the sex of the eyes. We also present a meta-analysis of the seven studies of watching eye effects in the Dictator Game published to date. Combined, these studies total 887 participants, and show that although watching eyes do not reliably increase mean donations, they do reliably increase the probability of donating something rather than nothing (combined odds ratio 1.39). We conclude that the watching eyes effect in the Dictator Game is robust, but its interpretation may require refinement. Rather than making people directionally more generous, it may be that watching eyes reduce variation in social behavior.     

The ontogeny of human laughter

Human adult laughter is characterized by vocal bursts produced predominantly during exhalation, yet apes laugh while exhaling and inhaling. The current study investigated our hypothesis that laughter of human infants changes from laughter similar to that of apes to increasingly resemble that of human adults over early development. We further hypothesized that the more laughter is produced on the exhale, the more positively it is perceived. To test these predictions, novice (n = 102) and expert (phonetician, n = 15) listeners judged the extent to which human infant laughter (n = 44) was produced during inhalation or exhalation, and the extent to which they found the laughs pleasant and contagious. Support was found for both hypotheses, which were further confirmed in two pre-registered replication studies. Likely through social learning and the anatomical development of the vocal production system, infants'' initial ape-like laughter transforms into laughter similar to that of adult humans over the course of ontogeny.     

It's funny because we think it's true: laughter is augmented by implicit preferences

This study tests the folk psychological belief that we find things funny because we think they are true. Specifically, it addresses the relationship between implicit preferences and laughter. Fifty-nine undergraduate Rutgers University students (33 females and 26 males) from ethnically diverse backgrounds were videotaped while watching a white stand-up comedian for 30 min. Positive emotional expression associated with laughter was later scored using the facial action coding system (FACS). Computer-timed Implicit Association Tests (IATs) were used to measure a subject's implicit preferences for traditional gender roles and racial preferences (blacks vs. whites). Results show that participants laughed more in response to jokes that matched their implicit preferences (e.g., those with stronger implicit preferences for whites laughed more at racially charged material). Implications for the evolution of humor, and laughter as a hard-to-fake signal of preferences, are discussed.     

The Effect of Social Stress on Chronic Pain Perception in Female and Male Mice

The current investigations on social stress primarily point to the negative health consequences of being in a stressful social hierarchy. The repetitive nature of such stressors seems to affect behavioral response to pain both in rodents and humans. Moreover, a large discrepancy in the possibility of social stresses affecting pain perception in the two genders exists. The present study examined the effect of chronic social stress on nociceptive responses of both sexes by implementing of food deprivation, food intake inequality and unstable social status (cage-mate change every 3 days) for a period of 14 days in 96 Balb/c mice. In this regard we injected 20 µl formalin 2% into the plantar surface of hind paw at the end of stress period and scored pain behaviors of all subjects, then serum concentrations of proinflammatory cytokines were measured. Our results showed that there was significant difference in chronic phase of formalin test following implementation of food deprivation and inequality (P<0.05) as compared to control group, so that pain perception was decreased considerably and this decline in inequality exposed subjects was well above isolated ones (P<0.05); whereas unstable social situation did not affect pain perception. Moreover, IL-1 and IL-6 concentrations in serum of stressed mice of both genders were well above control group (p<0.05). Finally, despite chronic pain perception in control and unstable male subjects was larger than females; the decrease of chronic pain perception in male stressed animals (poverty and inequality experienced subjects) was much more than stressed females. These results revealed that although food deprivation and social inequality can induce hypoalgesia, some socioeconomic situations like social instability don''t affect pain sensation, whereas there were similar increases of proinflammatory cytokines level in all socially stressed subjects. In addition, males display larger hypoalgesic responses to inequality as compared with females.     

Sharing the joke: the size of natural laughter groups

Recent studies suggest that laughter plays an important role in social bonding. Human communities are much larger than those of other primates and hence require more time to be devoted to social maintenance activities. Yet, there is an upper limit on the amount of time that can be dedicated to social demands, and, in nonhuman primates, this sets an upper limit on social group size. It has been suggested that laughter provides the additional bonding capacity in humans by allowing an increase in the size of the “grooming group.” In this study of freely forming laughter groups, we show that laughter allows a threefold increase in the number of bonds that can be “groomed” at the same time. This would enable a very significant increase in the size of community that could be bonded.     

Catecholamine release from isolated guinea pig lungs during sympathetic stimulation with varied ventilation and perfusion.

This study was performed to elucidate catecholamine release in the pulmonary circulation of isolated lungs due to the sympathetic nerve stimulation and to assess the experimental conditions which can modify the release, i.e., stimulus intensity, ventilation state of the lung and flow rate of perfusion. In artificially ventilated lungs, electrical stimulation of stellate ganglions evoked large noradrenaline efflux from the lung, but adrenaline efflux was below the detection limit, and dopamine was not detected in any case. In the unventilated preparations, the lung parenchyma were not bleached and the arterial pressure was significantly higher than in ventilated preparations. Noradrenaline efflux from the unventilated group was significantly lower than that from the ventilated preparations. The effect of the perfusion flow rate was investigated under pressure-operated ventilation. The pulmonary arterial pressure (Pa) was not varied at 5-10 ml min-1, but it was increased significantly at 20 ml min-1. Noradrenaline efflux was also increased significantly at 20 ml min-1. These results indicate that noradrenaline was the catecholamine exclusively released from pulmonary vasculature due to the sympathetic nerve stimulation, and that both ventilation and the perfusion flow rate could affect the release. The concomitant increase in arterial pressure indicates that noradrenaline efflux would be affected by the alteration in resistive small arteries. Circulatory change in these arteries is supposed to be one of the factors that modify noradrenaline release from the lungs. The analysis of noradrenaline should be a useful method to evaluate the sympathetic effect on the pulmonary vasculature.     

Synchrony and exertion during dance independently raise pain threshold and encourage social bonding

Group dancing is a ubiquitous human activity that involves exertive synchronized movement to music. It is hypothesized to play a role in social bonding, potentially via the release of endorphins, which are analgesic and reward-inducing, and have been implicated in primate social bonding. We used a 2 × 2 experimental design to examine effects of exertion and synchrony on bonding. Both demonstrated significant independent positive effects on pain threshold (a proxy for endorphin activation) and in-group bonding. This suggests that dance which involves both exertive and synchronized movement may be an effective group bonding activity.     

Modulation of social behavior and dominance status by chronic pain in mice

The potential influence of pain on social behavior in laboratory animals has rarely been evaluated. Using a new assay of social behavior, the tube co‐occupancy test (TCOT), we assess propinquity—the tendency to maintain close physical proximity—in mice exposed to pain using subcutaneous zymosan or spared nerve injury as noxious stimuli. Our previous experience with the TCOT showed that outbred mouse sibling dyads show higher levels of tube co‐occupancy than stranger dyads. We find here that long‐lasting pain from spared nerve injury given to both mice in the dyad abolishes this effect of familiarity, such that strangers also display high levels of propinquity. We performed a separate experiment to assess the effect on dominance behavior of nerve injury to one or both mice of a dyad in which relative dominance status had been previously established via the confrontation tube test. We find that neuropathic pain given only to the dominant mouse reverses the relationship in male but not female mice, such that the previously subordinate mouse becomes dominant. These observations bolster the scant but growing evidence that pain can robustly affect social behavior in animals.     

The adaptive value of humor and laughter

Most explanations for humor neglect important types of humor, such as tickling and word play; or raise difficult evolutionary theoretical problems, such as group selection, dubious fitness benefits, and excessive complexity of design; or ignore the data on humor and laughter. The present theory was based on the following observations. Tickling entails a mock attack at vulnerable body spots, and may provide youngsters with practice in defending themselves. The child's laughter is pleasant and encourages the tickler to persist. Similarly, juvenile primates including children encourage roughhousing by laughter and other emotional expressions. We also laugh at humorous content that provides striking counter-examples (incongruities), as in word play, or that informs us about fitness-relevant topics such as sexual, aggressive, and social poise scenarios. The present theory is that the pleasure of humor motivates us to seek out poignant, fitness- enhancing input of this sort. Laughter evolved to allow us to continue to recieve amusement. Laughter is a pleasant social signal that prompts the humorist to persist in providing this edifying stimulation. In response to true wit, laughter conveys appreciation and gratitude—an intention to reciprocate for having received a stimulating idea. Thus, humor benefits both humorist and laughter. This theory and others are evaluated in the light of evolutionary principles and relevant data.     

Social Media Release Increases Dissemination of Original Articles in the Clinical Pain Sciences

A barrier to dissemination of research is that it depends on the end-user searching for or ‘pulling’ relevant knowledge from the literature base. Social media instead ‘pushes’ relevant knowledge straight to the end-user, via blogs and sites such as Facebook and Twitter. That social media is very effective at improving dissemination seems well accepted, but, remarkably, there is no evidence to support this claim. We aimed to quantify the impact of social media release on views and downloads of articles in the clinical pain sciences. Sixteen PLOS ONE articles were blogged and released via Facebook, Twitter, LinkedIn and ResearchBlogging.org on one of two randomly selected dates. The other date served as a control. The primary outcomes were the rate of HTML views and PDF downloads of the article, over a seven-day period. The critical result was an increase in both outcome variables in the week after the blog post and social media release. The mean ± SD rate of HTML views in the week after the social media release was 18±18 per day, whereas the rate during the other three weeks was no more than 6±3 per day. The mean ± SD rate of PDF downloads in the week after the social media release was 4±4 per day, whereas the rate during the other three weeks was less than 1±1 per day (p<0.05 for all comparisons). However, none of the recognized measures of social media reach, engagement or virality related to either outcome variable, nor to citation count one year later (p>0.3 for all). We conclude that social media release of a research article in the clinical pain sciences increases the number of people who view or download that article, but conventional social media metrics are unrelated to the effect.     

反复电针对慢性痛的累加治疗作用及其机制研究

本研究从基础和临床两方面观察了反复电针对慢性痛的累加治疗作用,并结合疼痛患者及慢性痛动物模型中几种神经肽的放射免疫测定及相应受体拮抗剂的药理学研究结果,探讨了产生累加效应的可能机制。结果表明,在临床脊髓损伤性痉挛患者,１００Ｈｚ穴位体表电刺激有效地缓解痉挛并有累加效应;在临床慢性痛患者,２／１５Ｈｚ变频ＴＥＮＳ刺激有效地治疗疼痛并具有累加效应。在关节炎模型大鼠,电针刺激能产生明显的镇痛并具有累加效     

The animal nature of spontaneous human laughter

Laughter is a universally produced vocal signal that plays an important role in human social interaction. Researchers have distinguished between spontaneous and volitional laughter, but no empirical work has explored possible acoustic and perceptual differences. If spontaneous laughter is an honest signal of cooperative intent (e.g., derived from play breathing patterns), then the ability to mimic these sounds volitionally could have shaped perceptual systems to be attuned to aspects of spontaneous laughs that are harder to fake—features associated with phylogenetically older vocal control mechanisms. We extracted spontaneous laughs from conversations between friends and volitional laughs elicited by instruction without other provocation. In three perception experiments we found that, 1) participants could distinguish between spontaneous and volitional laughter, 2) when laugh speed was increased (duration decreased 33% and pitch held constant), all laughs were judged as more “real,” with judgment accuracy increasing for spontaneous laughter and decreasing for volitional laughter, and 3) when the laughs were slowed down (duration increased 260% and pitch altered proportionally), participants could not distinguish spontaneous laughs from nonhuman vocalizations but could identify volitional laughs as human-made. These findings and acoustic data suggest that spontaneous and volitional laughs are produced by different vocal systems, and that spontaneous laughter might share features with nonhuman animal vocalizations that volitional laughter does not.     

Mechanisms of the stimulation of insulin release by arginine-vasopressin in normal mouse islets

The mechanisms by which arginine-vasopressin (AVP) affects pancreatic B-cell function were studied in normal mouse islets. AVP produced a dose-dependent (0.1-1000 nM; EC50 approximately 1-2 nM) amplification of glucose-induced insulin release. This amplification was of slow onset and reversibility. AVP was ineffective when the concentration of glucose was less than 7 mM, but was still very effective in 30 mM glucose. The increase in insulin release produced by AVP was accompanied by small accelerations of 86Rb and 45Ca efflux from islet cells. Omission of extracellular Ca2+ accentuated the effect of AVP on 86Rb efflux, attenuated that on 45Ca efflux, and abolished that on release. Under no condition did AVP inhibit 86Rb efflux. AVP did not significantly affect cAMP levels, but increased inositol phosphate levels in islet cells, even in the absence of extracellular Ca2+. AVP did not affect the membrane potential in unstimulated B-cells and augmented glucose-induced electrical activity only slightly. This was not due to a direct action on ATP-sensitive K+ channels as revealed by patch-clamp recordings (whole cell and outside-out patches). In conclusion, AVP is not an initiator of insulin release, but it potently amplifies glucose-induced insulin release in normal mouse B-cells. This effect involves a stimulation of phosphoinositide metabolism, and presumably an activation of protein kinase C, rather than a change in cAMP levels or a direct control of the membrane potential.     

Physical growth in a transitional economy: the aftermath of South African apartheid

The economic transition in developing countries is not always the result of the change from a centrally-planned to a free-market economy, but may be found within an already existing free-market economy as a result of profound political change, as in South Africa. The release of Nelson Mandela in February 1990 heralded an end both to the political system of apartheid and to the concomitant social, political, and economic disenfranchisement of 30 million non-White people in South Africa. The first freely elected non-White government came to power in 1994 and initiated a number of social and economic reforms aimed at alleviating the worst consequences of apartheid. This paper examines the effect of post-apartheid economic and social transition on the growth and development of urban children. Over 4000 children born in Soweto and Johannesburg were enrolled in the Birth to Ten (BTT) birth-cohort study in 1990. Whilst these children were born with lower birth weights than in developed countries, they did grow strongly in infancy, particularly in weight, to reflect normal reference values for body mass index (BMI) by 1 year of age. While post-apartheid social and economic changes were expected to take some time to affect child growth and development, the rate of change has been slower than expected. Data from the BTT study demonstrate that the growth of White children continues to be superior to that of their non-White peers and differences that existed at birth and during infancy have not diminished during childhood and early adolescence. Whatever factors are changed at the national or community levels during economic (and social) transition in South Africa appear not yet to have resulted in improved child physical growth.     

Testosterone and cortisol release among Spanish soccer fans watching the 2010 World Cup final

This field study investigated the release of testosterone and cortisol of a vicarious winning experience in Spanish fans watching the finals between Spain and the Netherlands in the 2010 FIFA World Cup Soccer. Spanish fans (n = 50) watched the match with friends or family in a public place or at home and also participated in a control condition. Consistent with hypotheses, results revealed that testosterone and cortisol levels were higher when watching the match than on a control day. However, neither testosterone nor cortisol levels increased after the victory of the Spanish team. Moreover, the increase in testosterone secretion was not related to participants' sex, age or soccer fandom, but the increase in total cortisol secretion during the match was higher among men than among women and among fans that were younger. Also, increases in cortisol secretion were greater to the degree that people were a stronger fan of soccer. Level of fandom further appeared to account for the sex effect, but not for the age effect. Generally, the testosterone data from this study are in line with the challenge hypothesis, as testosterone levels of watchers increased to prepare their organism to defend or enhance their social status. The cortisol data from this study are in line with social self-preservation theory, as higher cortisol secretion among young and greater soccer fans suggests that especially they perceived that a negative outcome of the match would threaten their own social esteem.     

Mu-calpain is functionally required for alpha-processing of Alzheimer's beta-amyloid precursor protein

Alzheimer's beta-amyloid precursor protein (APP) is normally processed by an unidentified alpha-secretase. A unique feature of this protease is its high sensitivity to phorbol esters, yet the mechanism involved is unclear. We have previously reported that phorbol 12,13-dibutyrate (PDBu) activates calpain, a Ca2+-dependent protease, and PDBu-induced release of APPs (secreted APP) is sensitive to calpain inhibitors, suggesting that calpain is involved in APP alpha-processing. In the present study, we found that PDBu markedly promoted the expression of both mu- and m-calpains in cultured fibroblasts. Dose-response and time course studies revealed that mu-calpain was more sensitive to PDBu than m-calpain and the temporal course of the mu-calpain change coincides better with that of APPs release. Moreover, the stimulatory effect of PDBu on mu-calpain was selectively blocked by mu-calpain-specific siRNA (small interference RNA) and the blockage was accompanied by a concomitant decrease in APPs release. In contrast, m-calpain siRNA did not affect APPs release significantly. Measurement of amyloid beta protein (Abeta) release in the mu-calpain siRNA-treated cells indicated that Abeta40 and Abeta42 levels inversely changed in relation to APPs, and the changes in Abeta42 were more prominent than in Abeta40. Together, these data suggest that calpain, particularly mu-calpain, is a potential candidate for alpha-secretase in the regulated APP alpha-processing, and that changes in this protease can affect the outcome of the overall APP processing.