Group-living offers both benefits (protection against predators, access to resources) and costs (increased ecological competition, the impact of group size on fertility). Here, we use cluster analysis to detect natural patternings in a comprehensive sample of baboon groups, and identify a geometric sequence with peaks at approximately 20, 40, 80 and 160. We suggest (i) that these form a set of demographic oscillators that set habitat-specific limits to group size and (ii) that the oscillator arises from a trade-off between female fertility and predation risk.

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.

Dancing is a universal human activity that involves exertive rhythmic movement to music. It is often conducted in a social environment and often involves synchronization. It has been found to cause dancers to bond socially. Like conversation, it has been suggested that dancing may be an inexpensive form of social bonding, in that both activities facilitate efficient group bonding by allowing multiple individuals to bond simultaneously. However, no previous study has systematically observed the size of naturally occurring dance groups. During unobtrusive observation of natural dance and conversation behavior, we found that the cumulative number of dance partners (cumulative group) was greater than the number of partners at any one moment (instantaneous group), whereas no such difference was found for conversation. Additionally, the length of uninterrupted engagement (bout) was negatively predicted by group size in conversation but not dance groups, and it was significantly longer in conversation groups than dance groups. Finally, instantaneous group size was significantly larger in dance than conversation groups, and also positively related to time spent synchronizing in dance groups. Together, these results suggest that dance may allow a larger number of individuals to simultaneously engage with each other than conversation does because (i) more rapid partner switching increases cumulative broadcast group; and (ii) synchrony facilitates simultaneous interaction with multiple individuals, allowing for larger instantaneous groups. We conclude that the capacity for information transfer provided by language comes at a cost in terms of social bonding, and that dance may have played an important role in bonding large hominin social groups.

Why are some people interested in complex literature and others not? This study experimentally investigated this question by assessing what cognitive traits moderated responses to literary and less-literary fictional vignettes. Specifically, participants were exposed to two variants of a celebrated literary text, one altered so as to remove overtly literary elements. A moderation analysis was performed on responses with respect to three variables: need for cognition (NC); meaning in life (measured in two subscales, search for meaning (SM) and presence of meaning (PM)); and intentionality/mentalising ability (IM). Results showed that SM moderated interpretive response to the textual variation, such that those with increasing scores on the SM scale were increasingly more likely to rate the literary vignettes as worthy of appreciation. This result, in turn, gave grounds for a second study that investigated the role played by cloze values in identifying a text as 'literary'. The latter study showed that the literary and less literary vignettes exhibited significant differences in cloze values. Taken together, these studies suggest that differences in responsiveness to literary materials may well be driven by pre-existing cognitive factors.

Does reading fiction improve mental health and well-being? We present the results of five studies that evaluated the impact of five forms of exposure to fiction. These included the effects of recalling reading fiction, of being prescribed fiction, of discussing fiction relative to non-fiction, and of discussing literary fiction relative to best-seller fiction. The first three studies directly recruited participants; the final two relied on scraped social media data from Reddit and Twitter. Results show that fiction can have a positive impact on measures of mood and emotion, but that a process of mnemonic or cognitive consolidation is required first: exposure to fiction does not, on its own, have an immediate impact on well-being.