Progress Daily

Matthew Hertenstein asked alumni of his university to answer questions about their current sexual relationships and whether they had ever been divorced (”Smile intensity in photographs predicts divorce later in life”; .pdf file here).
His team then looked up pictures of their volunteers in the university’s yearbooks and graded the degree of their smiles. The less a person smiled the more likely he or she was to have been divorced over the course of a lifetime.

The study looked at over 600 alumni & a group of 55 non-alumni (the latter were asked to send in photos of themselves, but were not told that the study was about smiling). The researchers rated the photos of the subjects on a scale of 2 to 10.

The relationship between smiling and divorce even held up among the non-alumni who sent in photographs of themselves as children.

The never-divorced had their smiles rated on average at 5.9 for alumni and 5.2 for non-alumni, while the divorced scored about 5.1 and 4.4, respectively. The lowest-scoring people were 3 times more likely than the biggest smilers to divorce.

“Life in thin slices, The Economist

Just over 25% of the world’s population (1.4B people), lived in extreme poverty in 2005, according to a report released this month from the World Bank (”Global Economic Prospects 2009: Long-term prospects and poverty forecasts“). This has fallen from 42% in 1990, when the bank first published its global poverty estimates. All regions of the world have seen gains. Rapid economic growth east Asia in particular has led to a dramatic decline in global poverty. In China the share of the population getting by on $1.25 a day, or less, fell from 60% to 16%.

“Falling back again?,” The Economist

A new study by Andrew Leigh (”Does Size Matter in Australia?” — .pdf file here) examined health and income data from almost 20,000 Australians and found that for men each additional 20 centimeters (4 inches) of height was correlated with an additional 3% in hourly wages.

The “height premium” was 2% per 10 cms for women.

For men, every 5 cms (2 inches) above the average height of 178cms (5 feet 10 inches) was correlated with an increase equivalent to that of an extra year’s experience in the labor force.

This result held constant across factors such as age, race, family background, experience and education. In contrast to other studies, being overweight did not appear to decrease earnings.

“Study finds tall people at top of wages ladder”

Income is very heritable.

A study by Samuel Bowles & Herbert Gintis (”The Inheritance of Inequality,” 2002) found that identical twins’ incomes have a correlation of .56, versus .36 for fraternal twins. Using standard formulae, this implies that genetic factors explain 40% of the variance of income, family environment 16%, and non-shared environment 44%.

Using different data, David Cesarini gets income correlations of .54 for identicals versus .27 for fraternals, implying that genes explain 56% of the variance, shared environment -1%, and non-shared environment 45%.

“Is Greed in the Genes?,” by Bryan Caplan

Nicos Nicolaou’s research team used quantitative genetics techniques to compare the entrepreneurial activity of 870 pairs of monozygotic (MZ) and 857 pairs of same-sex dizygotic (DZ) twins from the UK, and found relatively high heritability for entrepreneurship, with little effect of family environment and upbringing.

Because MZ twins share all of their genetic composition and DZ twins share half of their genetic material on average, differences in the concordance between entrepreneurial activity of MZ and DZ twins can be attributed to genetic factors.

Studies of MZ and DZ twins raised together and apart have shown that the MZ twins raised apart are consistently more similar than DZ twins raised together.

Many parents are misinformed or make erroneous evaluations about the zygosity of their twins, leading some parents to raise their DZ twins as MZ twins and other parents to treat their MZ twins as DZ twins. Studies have shown that in cases where parents made erroneous conclusions about the zygosity of their twins, it was actual, rather than perceived zygosity that predicted similarity between twins.

The researchers estimate that 48% of the variance in the propensity to become self-employed is explained by genetic factors. None of the variance in self-employment can be attributed to shared environmental factors, while 52% can be attributed to non-shared environmental factors plus measurement error.

The researchers re-ran the analysis adjusting the model for potential confounders - income, education, marriage, age, race, and immigrant status - that have been shown to be associated with entrepreneurship. The heritability estimates for self-employment, drop only to 41% when these variables are included.

To identify the mechanism through which genetic factors operate, the researchers examined the respondents attitude toward entrepreneurship through an item that asked them to indicate, on a scale from one (a very good career) to five (a very bad career), their view of entrepreneurship as a career. The best fitting model to explain the variance in attitudes included shared and unshared environmental factors. None of the variance was explained by genetic factors, indicating that the mechanism through which these factors affect the tendency to become an entrepreneur is not through attitudes toward the vocation.

“Is the Tendency to Engage in Self-employment Genetic?” (.pdf file here), by Nicos Nicolaou, Scott Shane, Tim D. Spector, and others

Genome sequencing equipment has been improving even faster than microprocessor performance, which doubles roughly every 18 months (”Moore’s law“).

“Getting personal,” The Economist

According to research by Ivan Arreguín-Toft, in asymmetric military conflicts (those where one party possessed, on average, ten times the population and armed forces of their adversary) during the past two centuries the weak actors won nearly a third of the time.

When divided into four 50-year periods, strong actors lost to the weak more and more often. By the final 50-year period, the weak won a majority of engagements.

Strong powers excel at large, mechanized, combined-arms militaries in relatively open terrain. But small powers have increasingly used an indirect strategy that trades the protection of population for time.

Of the 202 lopsided conflicts in Arreguín-Toft’s database, the underdog fought conventionally 152 times — and lost 119 of those times. When they used an unconventional strategy they won almost two-thirds of the time. (”How David Beats Goliath,” by Malcolm Gladwell)

“How a superpower can end up losing to the little guys“