Connections

Social Dependence and Independence

Does a spoon full of sugar make aggression go down?

Does a spoon full of sugar make aggression go down?

     The potential for conflict pervades modern life. Drivers pound their horns, co-workers criticize, and close relationship partners snub attempts for closeness. Yet, most confrontations do not result in aggression. Why? Sugar may be a sweet substitute for aggression. Lemonade
     Ever wondered why people talk about aggression so much? Sure, aggression and violence might sell your video game, record, or movie. But most people spend most of their days in peace and, when confrontation occurs, in reconciliation.
     This isn't true of everyone. In fact, most, if not all, people have been in a fight. Yes, you've been in a fight. It's okay, so have all of the other people you know. The main catch, however, is that the fight occurred when you were around two years old. The eminent psychologist Richard Tremblay has shown that the most aggressive people on this planet are toddlers. Yes, toddlers are more aggressive than prison inmates and gang members. They just don't cause as much physical damage with their aggressive blows.
     What keeps our aggressive urges at bay? Self-control. As we mature, we learn to control our aggressive impulses. And the costs of aggression are immense. Kids who behave aggressively are rejected by their peers. Adults who behave aggressively are rejected by society through imprisonment. Brain development plays a role, and so does metabolic energy. Energy is needed to control one's impulses. Hence, giving people a boost of energy should reduce their aggression. And people who have problems breaking down glucose into energy (i.e., amino acids) should be at risk for behaving aggressively.
     In a paper that is "in press" at the journal Aggressive Behavior, my colleagues and I decided to put this idea to the test. In one study, we brought men and women to a laboratory and had them drink a glass of lemonade. By the flip of a coin, half of the participants drank lemonade sweetened with sugar. Yummy. The other half drank lemonade sweetened with a sugar substitute. After that, participants played a game where they could behave aggressively toward a stranger by blasting the stranger with intense noise.
     What do you think happened? Yep, people who drank the sugary lemonade behaved less aggressively compared to people who drank the lemonade with fake sugar. So, we had some promising results. But we wanted to do more.
Next, we wanted to see whether people who had metabolic problems were also at risk for behaving aggressively. My student, Tim Deckman, had people report their diabetic symptoms, their self-control, and their aggressive personality. The more diabetic symptoms people had, the worse self-control they had. Diabetic symptoms also related to having a more aggressive personality.
     It doesn't stop there. In a third study, we harvested information about how many people in each U.S. state had diabetes and correlated that with the murder rate in each state. The higher number of people with diabetes, the higher the murder rate.
     Finally, we went global. We obtained information about the number of people in over 100 countries had a glucose deficiency disorder-glucose-6-phosphate dehydrogenase deficiency-and the number of killings in each country. Like the U.S. data, the more people in country who had this metabolic disorder, the more killings there were in that country.
     To be sure, a lot of these data are correlational, which means that we can't be sure what causes what. But this work makes a consistent point: metabolic energy plays a role in predicting aggressive behavior. Although having a box of Hot Tamales certainly won't cure the world of aggression and violence, think carefully about the next time you let your blood sugar drop.

C. Nathan DeWall is an assistant professor of psychology at the University of Kentucky.

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