Eiluned Pearce

Social laughter is correlated with an elevated pain threshold

Although laughter forms an important part of human non-verbal communication, it has received rather less attention than it deserves in both the experimental and the observational literatures. Relaxed social (Duchenne) laughter is associated with feelings of wellbeing and heightened affect, a proximate explanation for which might be the release of endorphins. We tested this hypothesis in a series of six experimental studies in both the laboratory (watching videos) and naturalistic contexts (watching stage performances), using change in pain threshold as an assay for endorphin release. The results show that pain thresholds are significantly higher after laughter than in the control condition. This pain-tolerance effect is due to laughter itself and not simply due to a change in positive affect. We suggest that laughter, through an endorphin-mediated opiate effect, may play a crucial role in social bonding.

New insights into differences in brain organization between Neanderthals and anatomically modern humans

Previous research has identified morphological differences between the brains of Neanderthals and anatomically modern humans (AMHs). However, studies using endocasts or the cranium itself are limited to investigating external surface features and the overall size and shape of the brain. A complementary approach uses comparative primate data to estimate the size of internal brain areas. Previous attempts to do this have generally assumed that identical total brain volumes imply identical internal organization. Here, we argue that, in the case of Neanderthals and AMHs, differences in the size of the body and visual system imply differences in organization between the same-sized brains of these two taxa. We show that Neanderthals had significantly larger visual systems than contemporary AMHs (indexed by orbital volume) and that when this, along with their greater body mass, is taken into account, Neanderthals have significantly smaller adjusted endocranial capacities than contemporary AMHs. We discuss possible implications of differing brain organization in terms of social cognition, and consider these in the context of differing abilities to cope with fluctuating resources and cultural maintenance.

The ice-breaker effect: singing mediates fast social bonding

It has been proposed that singing evolved to facilitate social cohesion. However, it remains unclear whether bonding arises out of properties intrinsic to singing or whether any social engagement can have a similar effect. Furthermore, previous research has used one-off singing sessions without exploring the emergence of social bonding over time. In this semi-naturalistic study, we followed newly formed singing and non-singing (crafts or creative writing) adult education classes over seven months. Participants rated their closeness to their group and their affect, and were given a proxy measure of endorphin release, before and after their class, at three timepoints (months 1, 3 and 7). We show that although singers and non-singers felt equally connected by timepoint 3, singers experienced much faster bonding: singers demonstrated a significantly greater increase in closeness at timepoint 1, but the more gradual increase shown by non-singers caught up over time. This represents the first evidence for an ‘ice-breaker effect’ of singing in promoting fast cohesion between unfamiliar individuals, which bypasses the need for personal knowledge of group members gained through prolonged interaction. We argue that singing may have evolved to quickly bond large human groups of relative strangers, potentially through encouraging willingness to coordinate by enhancing positive affect.

Latitudinal variation in light levels drives human visual system size

Ambient light levels influence visual system size in birds and primates. Here, we argue that the same is true for humans. Light levels, in terms of both the amount of light hitting the Earths surface and day length, decrease with increasing latitude. We demonstrate a significant positive relationship between absolute latitude and human orbital volume, an index of eyeball size. Owing to tight scaling between visual system components, this will translate into enlarged visual cortices at higher latitudes. We also show that visual acuity measured under full-daylight conditions is constant across latitudes, indicating that selection for larger visual systems has mitigated the effect of reduced ambient light levels. This provides, to our knowledge, the first support that light levels drive intraspecific variation in visual system size in the human population.

Variation in the β-endorphin, oxytocin, and dopamine receptor genes is associated with different dimensions of human sociality

Significance Social behavior in mammals is underpinned by a number of social neuropeptides. Most studies, however, focus on a single neuropeptide (often oxytocin), and invariably only in the context of reproductive relationships. Here, we examine the associations between the six main social neuropeptides (endorphins, oxytocin, vasopressin, dopamine, serotonin, and testosterone) and social indices in three separate social domains (disposition, dyadic/romantic relationships, and social network). We show that each neuropeptide is quite specific in its domain of influence, although endorphins and dopamine influence all three social domains. The results suggest that the social importance of endorphins may have been underestimated. There is growing evidence that the number and quality of social relationships have substantial impacts on health, well-being, and longevity, and, at least in animals, on reproductive fitness. Although it is widely recognized that these outcomes are mediated by a number of neuropeptides, the roles these play remain debated. We suggest that an overemphasis on one neuropeptide (oxytocin), combined with a failure to distinguish between different social domains, has obscured the complexity involved. We use variation in 33 SNPs for the receptor genes for six well-known social neuropeptides in relation to three separate domains of sociality (social disposition, dyadic relationships, and social networks) to show that three neuropeptides (β-endorphin, oxytocin, and dopamine) play particularly important roles, with each being associated predominantly with a different social domain. However, endorphins and dopamine have a much wider compass than oxytocin (whose effects are confined to romantic/reproductive relationships and often do not survive control for other neuropeptides). In contrast, vasopressin, serotonin, and testosterone play only limited roles.

Is orbital volume associated with eyeball and visual cortex volume in humans

Abstract Background: In humans orbital volume increases linearly with absolute latitude. Scaling across mammals between visual system components suggests that these larger orbits should translate into larger eyes and visual cortices in high latitude humans. Larger eyes at high latitudes may be required to maintain adequate visual acuity and enhance visual sensitivity under lower light levels. Aim: To test the assumption that orbital volume can accurately index eyeball and visual cortex volumes specifically in humans. Subjects and methods: Structural Magnetic Resonance Imaging (MRI) techniques are employed to measure eye and orbit (n = 88) and brain and visual cortex (n = 99) volumes in living humans. Facial dimensions and foramen magnum area (a proxy for body mass) were also measured. Results: A significant positive linear relationship was found between (i) orbital and eyeball volumes, (ii) eyeball and visual cortex grey matter volumes and (iii) different visual cortical areas, independently of overall brain volume. Conclusion: In humans the components of the visual system scale from orbit to eye to visual cortex volume independently of overall brain size. These findings indicate that orbit volume can index eye and visual cortex volume in humans, suggesting that larger high latitude orbits do translate into larger visual cortices.

Singing together or apart: The effect of competitive and cooperative singing on social bonding within and between sub-groups of a university Fraternity

Singing together seems to facilitate social bonding, but it is unclear whether this is true in all contexts. Here we examine the social bonding outcomes of naturalistic singing behaviour in a European university Fraternity composed of exclusive “Cliques”: recognised sub-groups of 5–20 friends who adopt a special name and identity. Singing occurs frequently in this Fraternity, both “competitively” (contests between Cliques) and “cooperatively” (multiple Cliques singing together). Both situations were recreated experimentally in order to explore how competitive and cooperative singing affects feelings of closeness towards others. Participants were assigned to teams of four and were asked to sing together with another team either from the same Clique or from a different Clique. Participants (N = 88) felt significantly closer to teams from different Cliques after singing with them compared to before, regardless of whether they cooperated with (singing loudly together) or competed against (trying to singing louder than) the other team. In contrast, participants reported reduced closeness with other teams from their own Clique after competing with them. These results indicate that group singing can increase closeness to less familiar individuals regardless of whether they share a common motivation, but that singing competitively may reduce closeness within a very tight-knit group.

Tuning in to others: Exploring relational and collective bonding in singing and non-singing groups over time

Although it has been shown that singing together encourages faster social bonding to a group compared with other activities, it is unknown whether this group-level “collective” bonding is associated with differences in the ties formed between individual singers and individuals engaging in other activities (“relational” bonding). Here we present self-report questionnaire data collected at three time points over the course of seven months from weekly singing and non-singing (creative writing and crafts) adult education classes. We compare the proportion of classmates with whom participants were connected and the social network structure between the singing and non-singing classes. Both singers and creative writers show a steeper increase over time in relational bonding measured by social network density and the proportion of their classmates that they could name, felt connected with, and talked to during class compared to crafters, but only the singers show rapid collective bonding to the class-group as a whole. Together, these findings indicate that the process of creating a unitary social group does not necessarily rely on the creation of personal relationships between its individual members. We discuss these findings in the light of social cohesion theory and social identity theory.

Participants’ perspectives on the social bonding and well-being effects of creative arts adult education classes

Abstract Background: Evidence suggests that adult education classes have a positive impact on well-being, but whether this is true for all course activities is unknown. Methods: A UK adult education charity ran four singing classes, two craft classes and a creative writing class for the purpose of this study. Written responses to open questions about health, well-being and social lives were collected from participants at the end of the 7-month courses. Results: The classes enhanced well-being by improving mood and providing a sense of belonging. The classes helped participants develop self-confidence, create and strengthen relationships, and encouraged more active lives. Participants valued meeting people from their community and used these ties to access information about local opportunities. However, some participants reported negative experiences linked to unfavourable self–other comparison. Conclusions: These results highlight how regular adult education classes involving creativity can enhance well-being and help community integration regardless of the subject studied.

Functional Benefits of (Modest) Alcohol Consumption

Alcohol use has a long and ubiquitous history. Despite considerable research on the misuse of alcohol, no one has ever asked why it might have become universally adopted, although the conventional view assumes that its only benefit is hedonic. In contrast, we suggest that alcohol consumption was adopted because it has social benefits that relate both to health and social bonding. We combine data from a national survey with data from more detailed behavioural and observational studies to show that social drinkers have more friends on whom they can depend for emotional and other support, and feel more engaged with, and trusting of, their local community. Alcohol is known to trigger the endorphin system, and the social consumption of alcohol may thus have the same effect as the many other social activities such as laughter, singing and dancing that we use as a means of servicing and reinforcing social bonds.