The scientists worked with rats who were “mildly food deprived.” The rats were injected with ghrelin, which the stomach produces prior to food intake. The rats were also injected with angiotensin, a chemical that narrows blood vessels. The rats were already trained in multiple tasks that required them to demonstrate restraint in order to receive a food reward.
In one task, the rats learned to wait for a flashing light before they pressed on a lever and received a food pellet. If a rat didn’t wait for the light to flash and pressed the lever too soon, then it was penalized and missed the next chance to press for a pellet. After the ghrelin injection, the rats couldn’t resist their urge to press before the light, even though they understood they’d miss the pellet opportunity.
In another task, the rats learned the longer they waited to press the lever, the more treats they received. After the ghrelin injection, the rats wanted their pellets promptly and weren’t willing to wait to receive a reward. The authors concluded that ghrelin increases impulsivity and reduces self-control. For rats, being hungry was a physical state that led to an emotional response.
Grumpy Goat
Rats aren’t the only creatures to not be themselves when they are hungry. A 2021 study in Animal Behavior found that male fruit flies get more aggressive when food-deprived. The authors concluded that [...] dietary stress increases aggression, suggesting flies get ‘hangry.’
Similarly, another study looked at two groups of Apennines chamois, a horned goat-antelope that lives in the mountains of Spain, France and Italy. The scientists compared a herd that lived in a nutrient-rich area with a herd that lived in a sparser area. They found the herd that was more food-deprived had higher levels of aggression and stress response.
The hangry herd showed more aggression while foraging, which the authors concluded was likely an evolutionary strategy meant to help them secure needed nutrients and survive. Herd members were also more vigilant while grazing, and more likely to lift their heads to see if there was a threat from predators or other grass-loving chamois.
Hangry Humans,
But do humans get hangry? Studies find that hunger is linked to a wide range of self-control issues.
A 2013 paper in Psychology looked at the behavior of hungry people in 10 studies. Hungry people made more errors in tasks, and like the rats, they were more apt to have less self-control when their tummies were rumbling.
Most concerning, the authors also looked at data from war zones and found that societal hunger predicted war killings, which they attributed to a lack of self-control for their aggression. The authors also found that hungry people were more likely to think negative thoughts about racial minorities and have increased thoughts about death.
When trying to make sense of the results, the authors suggested that hormones like ghrelin might influence a person’s mood. They also thought a failure of self-control can be an emotional relief. Another idea was that negative attitudes or aggression was a type of self-preservation that kicks in when the body senses energy resources are low.
Not all scientists agree, however, that hanger is a thing. In a 2019 article published in Emotion, two psychologists suggested that hunger is a physiological state and that people give meaning to it when they perceive it as negative.
They recommended labeling the emotion in order to put feelings into words. It’s a process called affect labeling, and it can lessen the intensity, and perhaps even mute the feeling. Thus, identifying ‘I’m not myself because I’m hungry’ might just stop a person from having the hungrier.
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