Aggressive urges crop up, even for the most saintly people. What helps keep our aggressive urges at bay? Self-control. We can override our aggressive urges and do something more constructive.
But what makes self-control possible? Most of us struggle with self-control failure when we’re hungry. We might get angrier than usual, a term called ‘hangry.’
In a recent study published in the Proceedings of the National Academy of Sciences, my colleagues and I argue that glucose helps people control their aggressive urges. Glucose fuels the brain, and it takes brainpower to quiet our anger. If people have less brain fuel, they should behave more aggressively.
To test the idea, we recruited married couples, asked them to prick their fingers every day to measure their blood sugar levels, and then gave them a chance to express their aggression. Each day, people could stab a voodoo doll that represented their spouse with between 0 and 51 pins. On the last day of the study, people also completed a competitive reaction-time game against their partner, in which they could blast their partner with intense and prolonged noise. (Don’t worry, the game was rigged so that people never actually blasted their spouses.)
Low blood glucose related to greater aggression. The lower amount of sugar floated in people’s blood, the more pins they stuck into the voodoo doll and the more their blasted their spouse.