Many Americans went into personal debt before the economic recession hit the country in 2008. Why? For some men, the biggest factor may have been intense competition to find a spouse.That’s the suggestion of a new study co-authored by an MIT professor that analyzes the ways social settings can affect people’s propensity to save or spend money. Geographic areas with unusually high ratios of men to women, as the study notes, are correlated with high levels of personal debt; in follow-up lab experiments, the researchers found that men are more willing to spend money quickly in social settings with marked gender imbalances.“There is reason to believe that men are making financial decisions in a way that reflects the influence of the ratios of men and women,” says Joshua Ackerman, an assistant professor of marketing at the MIT Sloan School of Management and one of the researchers who performed the study. “Seeing more men around them in these environments activates a competitive mindset, which leads to a short-term, spend-now approach.”The study examined 134 cities across the United States, looking at gender ratios as well as the number of credit cards owned and the amount of consumer debt in each place. In some regions, these things vary widely.Consider the case of Macon and Columbus, two Georgia cities located within 100 miles of each other. In Columbus, there are 1.18 single men for every single woman, while in Macon, there are 0.78 single men for every single woman. As it happens, the average consumer debt in Columbus is $3,479 higher, per capita, than it is in Macon.To see if this could be related to gender issues, the researchers then set up a series of three experiments involving 205 people, who were presented with a series of photos on computer screens and asked to make a set of 20 financial choices; in one of the experiments, subjects were asked questions about how much they would be willing to spend on what the study calls “mating-related expenditures,” such as a Valentine’s Day gift, a dinner date and an engagement ring.When shown images with many more men than women, men in the study were willing to reduce their savings by 42 percent, and were willing to assume 84 percent more debt. “When men see more men than women in these photograph arrays, they become more likely to want to spend money more quickly, even to the point of going into debt,” Ackerman observes.The results are presented in a new paper, “The Financial Consequences of Too Many Men: Sex Ratio Effects on Saving, Borrowing, and Spending,” appearing in the January issue of the Journal of Personality and Social Psychology.The lead author of the paper is Vladas Griskevicius of the University of Minnesota’s Carlson School of Management; in addition to Ackerman, other co-authors of the paper are Joshua M. Tybur of the Netherlands’ VU University Amsterdam, Andrew W. Delton and Theresa E. Robertson of the University of California at Santa Barbara, and Andrew E. White of Arizona State University.Douglas Kenrick, a professor of psychology at Arizona State who is familiar with the study, calls it “important” and says that its conclusions “elegantly link to a broad set of findings on humans and other species” involving the effects of mating competition on decision making. “Some of our complicated mental decisions are actually manifestations of simpler, more biologically general processes,” Kenrick suggests.As Ackerman acknowledges, the study’s results are one piece of a larger puzzle about consumer habits during the credit-fueled spending boom that just ended. “The studies do show in direct ways how [these] ratios can affect people’s decision making, but I don’t think it’s the last chapter in this kind of research,” Ackerman says.For one thing, people in many types of social circumstances — not just in locations with imbalanced gender ratios — went into debt during the credit-fueled spending boom that preceded the recession, so spending in search of the ideal partner is just one of the reasons people live beyond their means.Ackerman and his colleagues also say they would like to study cross-cultural spending habits in future research — perhaps in China, which has a significant gender imbalance, but unlike the United States, has traditionally had high savings rates.“If competition is what’s really underlying this kind of spending, that should be fairly consistent across cultures,” Ackerman says. “But how those decisions get expressed might be much more culturally tinged. In China there’s a stronger norm toward giving gifts to a bride’s family. In that situation, spending money quickly isn’t necessarily going to lead to the best outcome. Instead, saving so that the amount of money you spend is worthwhile would make more sense.”