Brad Bushman has a drawer full of Clif bars in his desk, just in case. It’s not a diabetes quick-fix, but it does have to do with blood-sugar. It’s about aggression and self-control. It’s about not wanting to be hangry. It’s about marshmallows, voodoo dolls, and violent crime.
In the early 1960s, Stanford psychologist Walter Mischel performed his famous Marshmallow Test—he gave children a marshmallow to eat now, or two if they waited alone for 20 minutes. He followed up with the children years later and found that those who waited for the second marshmallow had generally been more successful. They had more activity in the prefrontal cortex of their brain, the region that controls so-called executive functions—thinking, reasoning, self-control.
In 1990, two criminologists published a book titled “A General Theory of Crime” in which they suggested that lack of self-control is the main driving force behind violent behavior, more significant than any other single cause.
“Aggression is really complex and is caused by a number of factors, but I really think aggression often starts when self-control stops.”
“Self-control can be strengthened just like muscles,” Bushman says from his place on the big red dot. He’s a professor of communication and psychology at Ohio State and a member of President Obama’s taskforce on gun violence. He has spent the last 25 years studying human aggression. “Aggression is really complex and is caused by a number of factors, but I really think aggression often starts when self-control stops.”
So Bushman, in his quest for insight into aggression and ways to curb it, conducted his own experiment, adding to the likes of the Marshmallow Test and “A General Theory of Crime.” He focused on the phenomenon of “hangriness,” the modern term for growing so hungry that you become angry. Since the brain uses 20 percent of our calories and self-control requires a lot of energy, he theorized that low blood-glucose levels would adversely affect the brain and cause an increase in aggressive behavior.
He and his fellow researchers asked 62 college students to take a taste-test in which half of the participants received lemonade with sugar, which has calories, and the other half got the drink with Splenda, which doesn’t. The students fasted for three hours before the study so their blood-glucose levels would be lower. After the taste-test, they were told to play a computerized game with an unseen opponent, and whoever lost got a sonic assault of noises people hate. The volume was set by the opponent beforehand, from level one (60 decibels) to level 10 (105 decibels)—the equivalent of a fire alarm going off in your headphones. Sure enough, the students who drank the lemonade with Splenda subjected their opponents to noises more than one full level louder on average than those who drank the sugary blend.
Bushman stops his talk and asks if the audience would like to hear a sample. He emits a 93-decibel blast, which sounds like a banshee getting sucked into a jet engine.
To see if the results carried over to people who aren’t strangers, the research team devised another experiment in which 107 married couples were given a voodoo doll, 51 pins, and devices to measure their blood-sugar levels. For 23 days, they were asked to calculate their blood-glucose and stab the voodoo dolls with pins based on how angry they were with their spouses before bed. Just like the previous experiment, those with lower glucose were more likely to display angry feelings, using nearly three times more pins than those with higher levels. The couples were then brought into the lab, and those with low glucose also gave their spouses louder and longer noise blasts that those with higher levels, replicating the findings of the study with college students.
The takeaway from Bushman’s work? His advice isn’t to curb aggressive urges with doses of sugar—in fact, that type of diet can lead to diabetes, and people suffering from the disease tend to be more aggressive. Instead, people should provide their brains with the fuel necessary to maintain self-control by eating a healthy diet.
And keep a Clif bar handy. Just in case.