Letters in 2018

Brain networks are characterized by nodes and hubs that determine information flow within and between areas. Bertolero et al. show that task-driven changes to hub and node connectivity increase modularity and improve cognitive performance.

Camerer et al. carried out replications of 21 Science and Nature social science experiments, successfully replicating 13 out of 21 (62%). Effect sizes of replications were about half of the size of the originals.

Akbarzadeh and Estrada mathematically characterize the properties of traffic flow and find that, in four different cities, there is more traffic not through the shortest paths, but through the communicability shortest paths, which assume an ‘all-routes’ flow.

A study of intimate partner violence among the Tsimané forager-horticulturalists of Bolivia finds evidence that male aggression is leveraged to increase marital fertility and a man’s individual fitness when spouses differ in preferred family size.

Humans can recognize emotions from facial expressions. Brooks and Freeman investigate the link between conceptual representation and visual perception of emotions and show that emotions that are represented as conceptually similar are perceived as similar.

Theories about the spread of Christianity are tested using comparative cross-cultural methods and historical data on 70 Austronesian cultures. Conversion was fastest in small and politically organized societies, but not impacted by social inequality.

Shortly after retrieval, memory undergoes a labile period during which it can be modified. This study shows that this reconsolidation phase shows the same behavioural and neural characteristics as the initial learning phase.

Experiments using economic games and hypothetical infectious disease scenarios show that uncertainty about a decision’s outcome reduces prosocial actions, but when the impact on others is made uncertain, prosociality increases.

Analyses of twin and genomic data show a significant influence of genetic factors on the co-development of conduct and emotional problems from childhood to adolescence. Those with co-developing symptoms may represent a clinical subgroup with higher genetic risk.

Category learning has been traditionally viewed as a high-level cognitive process independent of sensory systems. Rosedahl and colleagues demonstrate that procedural category learning is in fact dependent on low-level visual representations.

Through mathematical analysis, simulations and examples from real-world social networks, Fotouhi et al. demonstrate how establishing sparse interconnections between previously segregated, uncooperative societies can support the evolution of cooperation globally.

Analysing high-resolution mobility traces from almost 40,000 individuals reveals that people typically revisit a set of 25 familiar locations day-to-day, but that this set evolves over time and is proportional to the size of their social sphere.

Kaplan and colleagues find that, in virtual foraging environments in which resource availability is variable, over time, tolerated theft of the resources of others declines, as participants endogenously develop reciprocal exchange relationships to buffer risk.

Kavanagh and colleagues model global human population densities between 21,000 and 4,000 years ago and find that improved environmental conditions and increased potential for population growth facilitated the emergence of agricultural domestication.

By analysing the language of tweets around protests in Baltimore in 2015 and through behavioural laboratory experiments, Dehghani and colleagues find that moralization of protest issues leads to greater support for violence and increased incidence of violent protest.

Aral and Dhillon specify a class of empirically motivated influence maximization models that incorporate more realistic features of real-world social networks and predict substantially greater influence propagation compared with traditional models.

A personalized letter intervention that corrected parents’ misbeliefs about their child’s absences reduced chronic absenteeism by 10% and is significantly more cost effective than alternative current best practices.

Contest experiments among natural groups demonstrate that unequal sharing of contest spoils can override the effects of preexisting intergroup relations, prompting privileged individuals to choose considerably more offensive strategies, whereas disadvantaged group members resort to defensive strategies.

In the United States and India, people's folk conceptions of nationality are flexible, seeing it as more biological and fixed at birth or cultural and fluid, depending on the scenario. Belief in fluidity predicts positive attitudes to immigration.

An analysis of genetic influences on educational attainment and occupation in pre- versus post-Soviet-era Estonia shows that genetics has a much greater influence on social outcomes in a meritocratic society.