Saturday, November 16, 2013

On Correlations of Cultural Traits

Via someone on Facebook,
Linguistic Diversity and Traffic Accidents: Lessons from Statistical Studies of Cultural Traits


The recent proliferation of digital databases of cultural and linguistic data, together with new statistical techniques becoming available has lead to a rise in so-called nomothetic studies [1–8]. These seek relationships between demographic variables and cultural traits from large, cross-cultural datasets. The insights from these studies are important for understanding how cultural traits evolve. While these studies are fascinating and are good at generating testable hypotheses, they may underestimate the probability of finding spurious correlations between cultural traits. Here we show that this kind of approach can find links between such unlikely cultural traits as traffic accidents, levels of extra-martial sex, political collectivism and linguistic diversity. This suggests that spurious correlations, due to historical descent, geographic diffusion or increased noise-to-signal ratios in large datasets, are much more likely than some studies admit. We suggest some criteria for the evaluation of nomothetic studies and some practical solutions to the problems. Since some of these studies are receiving media attention without a widespread understanding of the complexities of the issue, there is a risk that poorly controlled studies could affect policy. We hope to contribute towards a general skepticism for correlational studies by demonstrating the ease of finding apparently rigorous correlations between cultural traits. Despite this, we see well-controlled nomothetic studies as useful tools for the development of theories

A diagram from the paper (available for free at the web page linked above)

A quote:

Furthermore, it is possible to demonstrate a chain of relationships between cultural variables (see figure 3): Linguistic diversity is linked with climate [73]. Climate affects the likelihood of cultural siestas [74]. Cultures that take siestas tend to have languages with less morphological complexity (t = 3.47, p = 0.001, see methods). Morphological complexity is linked with group size [1]. Group sizeis linked to the levels of extra-marital sex in a community (r = 20.54, p = 0.001, see methods). Levels of extra-marital sex have been linked to a language’s phoneme inventory [6]. Phoneme inventories have been linked to patterns of migration [3]. Migration patterns are linked to the level of political collectivism in a culture (r = 0.42, p = 0.004, see methods). Collectivism is
predicted by genetic factors [4,5]. There are also genetic correlates of linguistic tone [7]. Tonal languages co-occur with acacia trees
(t = 3.77, p = 0.0002, see methods). To bring the chain full-circle, the presence of Acacia nilotica also predicts a greater number of traffic accident fatalities, controlling for linguistic diversity, length of road network, GDP, distance from the equator, population size and population density (t = 3.26, p = 0.0014, see methods)