James O’Brien

Beauty by numbers

Art historians have been using statistical methods to classify ancient works since the 1970s, when computers were introduced to the field. By measuring the physical dimensions of clay pots and stoneware items whose origins are well established, for instance, scholars can identify the variables that link the pieces to specific cultures. That information, in turn, helps historians identify the provenance of newly discovered works.

This kind of quantitative approach is useful for studying simple objects like pottery, which can be characterized by a few variables, but it’s not typically used to examine sculpture or visual art. How could you quantify, say, the subtle iconographic elements that distinguish an ancient Phoenician ivory carving from one produced in nearby North Syria?

Art historian Amy Gansell ’98BC has done just that, and her solution involves one of the most sophisticated tricks of number crunching ever attempted in her field. As part of her Harvard dissertation, she recently scrutinized female figures depicted in hundreds of decorative ivories from first-millennial BCE Mesopotamia, recording the shapes of eyes, noses, and chins, whether hair is curly or if the women wear jewelry, and dozens of other details. Gansell then recruited Chris Wiggins, a Columbia associate professor of applied mathematics and applied physics, to examine the 32,000 resulting pieces of data. Wiggins employed a new, high-powered type of statistical analysis called “machine learning,” which can reveal hidden patterns and associations amid huge data sets. (Biologists use machine learning to untangle the human genome, and political scientists use it to comb election results for voting trends.)

Gansell used the technology to brush off what had become a dusty topic for art historians, revealing previously unobserved differences in how Phoenician and North Syrian artisans plied their trade. She discovered that among ivory carvings whose female forms have well-defined eyelids and nostrils that are delicately scooped out (rather than drilled straight through), 95 percent are from North Syria, as determined by previous studies. “No one would have noticed the association between those variables and the North Syrian origin simply by looking at the carvings,” says Gansell, who will defend her dissertation at Harvard this spring. “It provides one more tool for determining the provenance of ivories whose origins are unclear.”

Joanna Smith, a Columbia art history professor who uses quantitative methods to study Bronze Age ceramics and wasn’t involved in the study, says that Gansell’s methodology could be influential, especially if she can convince other scholars that her findings advance their understanding of ancient aesthetics. Adds Gansell, “Some art historians, I suspect, will dismiss my approach because research in the field typically isn’t data driven. But there’s a drawback to relying solely on impressionistic visual analysis: You can end up with entrenched ideas about what a particular culture’s art is supposed to look like. My methods can reveal new information, new ways of looking at these pieces.” —DJC

James O’Brien  

Pay for peace

Do UN peacekeepers really help countries experiencing internal conflict? Or, as military strategist Edward N. Luttwak and other scholars have argued, do they cause more violence in the long run by preventing civil wars from ending decisively?

Page Fortna, a Columbia political science associate professor, has conducted one of the first quantitative studies of UN peacekeeping missions and finds that they are, in fact, overwhelmingly successful. While the news media have focused on peacekeeping disasters, such as occurred in Somalia, the data on the ground tell another story: UN peacekeepers since the end of the Cold War reduced by 50 to 80 percent the chances of resumed fighting within five years of a cease-fire. That’s true, Fortna says, both for well-armed UN military operations with license to forcibly uphold a peace settlement, such as is under way now in Darfur, and for more pussyfooted missions invited to observe disarmament, elections, and political reforms.

The findings, reported in Fortna’s forthcoming book, Does Peacekeeping Work? (Princeton University Press), are based on her analysis of 60 civil wars whose parties reached a cease-fire or had one imposed by the UN between 1989 and 2000; UN peacekeepers intervened in about half the conflicts. Fortna accounts for variables such as the length of fighting, if neighboring nations stoked the flames, and whether the country had democratic governance before or after the war. She says that among the most important factors in maintaining peace is one considered distasteful by many policymakers: cash handouts.

“Mozambique became peaceful in the 1990s partly because the UN paid rebel leaders not to go back to war,” says Fortna, who has done extensive fieldwork in the country. “It was blatant co-option, and it worked. Meanwhile, Mozambican government officials benefited from having thousands of peacekeepers and aid workers pouring into the country, renting homes, and spending money. That provided a major boost for a bad economy. Everybody knew that if war returned, the money would be gone.” —DJC

  James O’Brien

Fiscal discipline

Congress is expected soon to draft tough new regulations for the mortgage industry, partly to ensure that lenders stop pushing complicated home loans on people who don’t understand them. Lawmakers have even discussed banning a subprime loan called the “option-ARM” (for adjustablerate mortgage), which can send borrowers deeper into debt by letting them pay less than what they owe in interest, adding the excess to their principal.

But a new study by Tomasz Piskorski, a Columbia Business School finance and economics professor, and Alexei Tchistyi, a New York University finance professor, finds that the option-ARM is actually the best mortgage available — albeit only in an ideal world where borrowers show perfect discipline in making payments.

How could a mortgage aimed at people with shaky finances be the best? What makes the option-ARM dangerous, the researchers say, should be a big advantage: Its low monthly payments give borrowers maximum flexibility managing their debt so they’re able to keep up with payments after losing a job, going through a divorce, or incurring unexpected medical bills. The trick to making an option-ARM work, they say, is to pay more toward the note whenever you can afford to, just as you’d pay off a credit card. The problem is that’s not the way many Americans have used the option-ARM. Instead, they’ve chosen to pay only the minimum due every month, according to news reports. Then, the principal mushrooms, higher rates kick in, and foreclosure often looms.

Piskorski and Tchistyi demonstrate through mathematical modeling that the flexibility of the option-ARM should more than offset the costs of special stipulations lenders typically place on the loans — linking minimum payments to the federal interest rate, for instance, or including stiff prepayment penalties. (Their study assumes that borrowers, except in times of hardship, will make monthly payments large enough to pay off their mortgage in typical fashion.)

The current mortgage crisis, Piskorski said in a recent interview with Columbia, occurred partly because banks and lending agencies issued alternative home loans like the option-ARM to borrowers who simply couldn’t afford them. Lenders hoped housing appreciation would enable borrowers eventually to pay off their debts by flipping their homes or by refinancing, he says.

But Piskorski insists that the federal government, rather than strictly regulate or eradicate option-ARMs, should instead require Americans to take training seminars and pass tests proving that they understand how the loans work before they obtain one. “Alternative mortgages have pumped tens of billions of dollars into our economy by extending credit to people who otherwise couldn’t get a home loan,” he said. “Anything we can do to keep borrowing restraints relaxed will be enormously beneficial.” —DJC