The cultural evolution of love in literary history.

Since the late nineteenth century, cultural historians have noted that the importance of love increased during the Medieval and Early Modern European period (a phenomenon that was once referred to as the emergence of 'courtly love'). However, more recent works have shown a similar increase in Chinese, Arabic, Persian, Indian and Japanese cultures. Why such a convergent evolution in very different cultures? Using qualitative and quantitative approaches, we leverage literary history and build a database of ancient literary fiction for 19 geographical areas and 77 historical periods covering 3,800 years, from the Middle Bronze Age to the Early Modern period. We first confirm that romantic elements have increased in Eurasian literary fiction over the past millennium, and that similar increases also occurred earlier, in Ancient Greece, Rome and Classical India. We then explore the ecological determinants of this increase. Consistent with hypotheses from cultural history and behavioural ecology, we show that a higher level of economic development is strongly associated with a greater incidence of love in narrative fiction (our proxy for the importance of love in a culture). To further test the causal role of economic development, we used a difference-in-difference method that exploits exogenous regional variations in economic development resulting from the adoption of the heavy plough in medieval Europe. Finally, we used probabilistic generative models to reconstruct the latent evolution of love and to assess the respective role of cultural diffusion and economic development.

Simple questionnaires outperform behavioral tasks to measure socio-emotional skills in students.

Recent empirical research has shown that improving socio-emotional skills such as grit, conscientiousness and self-control leads to higher academic achievement and better life outcomes. However, both theoretical and empirical works have raised concerns about the reliability of the different methods used to measure socio-emotional skills. We compared the reliability and validity of the three leading measurements methods-a student-reported questionnaire, a teacher-reported questionnaire, and a behavioral task-in a sample of 3997 French students. Before analyzing the data, we polled 114 international researchers in cognitive development and education economics; most researchers in both fields predicted that the behavioral task would be the best method. We found instead that the teacher questionnaire was more predictive of students' behavioral outcomes and of their grade progression, while the behavioral task was the least predictive. This work suggests that researchers may not be using optimal tools to measure socio-emotional skills in children.