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Uncommon Knowledge

Sorry, population control is not an environmental cure-all

And more surprising insights from the social sciences


Some environmentalists argue that having large families is irresponsible, given the demands that modern-day people place on the environment. But a new study by environmental scientists in Australia suggests that population control is not a near-term solution. Their models indicate that even major reductions in fertility would not make a big dent in population by the year 2100. You’d have to enforce a global one-child policy by mid-century—and assume no improvements in longevity—to cut population in half by 2100. Otherwise, even a war or pandemic that kills 2 billion people mid-century would still leave over 8 billion people by 2100. The scientists conclude that this suggests our sustainability efforts would be better spent by “rapidly reducing our footprint as much as possible through technological and social innovation, devising cleverer ways to conserve remaining species and ecosystems, encouraging per capita reductions in consumption of irreplaceable goods, and treating population as a long-term planning goal.”

 Bradshaw, C. & Brook, B., “Human Population Reduction Is Not a Quick Fix for Environmental Problems,” Proceedings of the National Academy of Sciences (forthcoming).

$0.99, the rationalist’s price

The 99-cent store might be fine for practical necessities, but it seems consumers would rather spend an even dollar when they’re buying with their hearts. That’s the lesson from a series of experiments on how people react to round-number prices for products with different purposes. When considering a bottle of champagne, for example, people were more interested in buying it when it had a round-number price, but when considering a calculator, people were less interested in buying it when it had a round-number price. This was true even for the same product: People were more impressed with a camera—and its pictures—at a round-number price when it was to be used on a family vacation, but were less impressed when it was to be used for a class project. Even when just asked to consider their own feelings, people were more interested in buying a product when it had a round-number price, whereas asking people to think deliberately caused them to be more interested in buying a product when it had a non-round-number price.

 Wadhwa, M. & Zhang, K., “This Number Just Feels Right: The Impact of Roundedness of Price Numbers on Product Evaluations,” Journal of Consumer Research (forthcoming).

I see gender equality in your hands

The length of the index finger relative to the length of the ring finger—known as the 2D:4D ratio—has been associated with levels of prenatal testosterone, such that people with lower 2D:4D ratios are presumed to have been exposed to more testosterone in the womb. Researchers are now claiming that this trait varies not only at the individual level, but also at the national one. Data from thousands of white individuals in predominantly white countries (to control for ethnic differences in 2D:4D) revealed that countries where women had relatively lower 2D:4D ratios also had relatively more women in politics and the workforce, even controlling for gross national income per capita.

 Manning, J. et al., “Digit Ratio (2D:4D) and Gender Inequalities across Nations,” Evolutionary Psychology (August 2014).

You’re not my type, but sure

Have you ever found yourself on a date with someone who, on paper, isn’t what you were looking for at all? It turns out that daters’ preferences in principle can get blindsided by another factor: compassion. In an experiment, single, heterosexual college students were shown dating profiles of other students. The researchers told some of the participants that these profiles represented actually available fellow students, while other participants were told that these profiles represented unavailable students. The participants then picked their favorite profile. Researchers then presented the participants with an unattractive picture or “deal-breaker” traits that were also supposedly from the profile. When participants thought the profile represented a potentially real date, they were significantly more willing to give out contact information—despite the negative details—than when they thought the profile was hypothetical, because they were worried about hurting the other student’s feelings. In other words, a lot of singles are too nice to say no.

 Joel, S. et al., “People Overestimate Their Willingness to Reject Potential Romantic Partners by Overlooking Their Concern for Other People,” Psychological Science (forthcoming).


Powerlust: it’s a class thing

People from disadvantaged backgrounds may have a harder time reaching the top for all sorts of practical reasons, but what if some of what’s holding them back is cultural? New research reveals that people from lower-class backgrounds are more reluctant to be Machiavellian in climbing the organizational ladder. Even at a top business school, students who had a lower-class childhood were less interested in taking a class on power. This reluctance wasn’t explained by a lower desire for power or a belief that their efforts wouldn’t be rewarded. Instead, they considered power-hungry behavior to be more distasteful. When they thought about power as a means for helping loved ones—rather than just for personal gain—the class-based differences disappeared.

Belmi, P., “Who Wants to Get to the Top? Class and Lay Theories about Power,” Stanford University (June 2014).

Kevin Lewis is an Ideas columnist.
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