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Reducing pollution has many benefits, but here’s one that’s surprising: It could help more baby boys to make it to term. Previous research has found that mothers in poor health are less likely to produce male offspring, with male fetuses more likely to be lost after conception; the theory is that this improves the mother’s Darwinian prospects because, under poor health conditions, female offspring tend to out-reproduce male offspring. Two economists used this relationship between maternal health and the sex ratio of her babies to infer the prenatal impact of the Clean Air Act. The estimates suggest that the Clean Air Act increased the probability of a baby boy by half a percentage point in counties subject to pollution reductions, especially for uneducated, young, single mothers. This implies that thousands of babies survived to term because of the Clean Air Act.

Sanders, N. & Stoecker, C., “Where Have All the Young Men Gone? Using Sex Ratios to Measure Fetal Death Rates,” Journal of Health Economics (forthcoming).

To teach tool-making, try language

How would you teach a child to tie his shoelaces? You wouldn’t just hand him a shoe that’s already laced and expect him to reverse-engineer it. You also wouldn’t just tie the shoe in silence as he watched. You’d want to actively teach him, by communicating with him. And there lies one key to the evolution of language, according to new research. In an experiment, participants were randomly assigned to learn via these different methods how to knap stone, as people had to do in making prehistoric stone tools. They learned much better when they were actively taught, especially with verbal communication, than when they were asked to learn via reverse engineering or passive observation. This suggests a way that the challenges—and benefits—of passing on tool-making skills could have driven the evolution of language as early as 2 million years ago, when hominins first became stone knappers.

Morgan, T. et al., “Experimental Evidence for the Co-Evolution of Hominin Tool-Making Teaching and Language,” Nature Communications (January 2015).

Hierarchy means victory! And death

Hierarchical teams get things done, but at a steep price. An analysis of thousands of Himalaya mountain-climbing expeditions revealed that climbing groups from countries that placed more value on hierarchy were more likely to get climbers to the summit. But they were also more likely to experience deaths, even controlling for other characteristics of the expedition and the home country. There were no such associations among solo expeditions (i.e., only one nonhired climber). The authors of the study—and experienced climbers—figure that hierarchical culture improves coordination but also suppresses dissent and disclosure.

Anicich, E. et al., “Hierarchical Cultural Values Predict Success and Mortality in High-Stakes Teams,” Proceedings of the National Academy of Sciences (forthcoming).

Skip the ‘responsible drinking’ ads

Many alcohol ads note that the viewer should drink “responsibly.” However, new research from psychologists in Britain suggests that these responsible-drinking messages may backfire. When young adults were offered what they believed to be alcoholic drinks, they drank more if there were responsible-drinking posters—compared to academic or health posters—on the wall in front of them.

Moss, A. et al., “The Effects of Responsible Drinking Messages on Attentional Allocation and Drinking Behavior,” Addictive Behaviors (forthcoming).

Richer people are less blue

Money can’t buy you love or happiness, but it may be able to buy you less sadness. A survey of Americans revealed that those with higher household income reported feeling less sad—but not necessarily happier—while doing various daily activities, whether watching TV, commuting, eating/drinking, or doing housework. The association between higher income and less sadness was not explained by differences in reported stress, time use, age, sex, ethnicity, family situation, education, or employment.

Kushlev, K. et al., “Higher Income Is Associated with Less Daily Sadness but Not More Daily Happiness,” Social Psychological and Personality Science (forthcoming).


Kevin Lewis is an Ideas columnist.
He can be reached at kevin.lewis.ideas@gmail.com.