Hunger is a complex thing. We've all heard of the term 'hangry' - when something as simple as skipping a meal can change your mood from pleasant into irrationally cranky.
But, as new research shows, 'hanger' might be more complicated than just a drop in blood sugar, and according to the researchers, it appears to be a complicated emotional response between biology, personality and environmental cues.
"We all know that hunger can sometimes affect our emotions and perceptions of the world around us, but it's only recently that the expression hangry, meaning bad-tempered or irritable because of hunger, was accepted by the Oxford Dictionary," said first author Jennifer MacCormack, from the University of North Carolina.
"The purpose of our research is to better understand the psychological mechanisms of hunger-induced emotional states - in this case, how someone becomes hangry."
First, the team conducted two online experiments with over 400 Americans to determine how hunger affected their emotions.
After determining how hungry the participants were through self-reflective surveys, they were shown images designed to induce a positive, negative, or neutral feeling. Then they were asked to rate an ambiguous image of a Chinese pictograph on a seven point scale from pleasant to unpleasant.
What the researchers found is that the hungry participants primed with a negative image were more likely to find the ambiguous Chinese pictograph unpleasant.
"The idea here is that the negative images provided a context for people to interpret their hunger feelings as meaning the pictographs were unpleasant," said MacCormack.
"So there seems to be something special about unpleasant situations that makes people draw on their hunger feelings more than, say, in pleasant or neutral situations."
In a third experiment, the researchers undertook a particularly gruelling laboratory experiment with nearly 250 university students.
"Psych 101 students, bless their heart," MacCormack told NPR's Angus Chen. "They didn't know this was a study about feeling hangry."
This time, 118 of the students were told to fast for 5 hours, and 118 were told to eat before the experiment.
When they got there, half the students in both groups were asked to write an essay focussing on their emotions, while the others just had to write an essay on a 'neutral, unemotional day'.
Then, in what sounds like the student equivalent of hell, all of them were put through a tedious computer exercise which was programmed to crash right near the end.
"I designed this fake task with coloured circles. The colours are really glaring and bright and hard to look at, and it's a hard task with a hundred trials," she said to NPR.
As if that wasn't enough, the researchers were then instructed to come into the room and blame the student for the computer crash.
"Oh, what buttons did you press? You must have caused the crash," MacCormack says. "Then we let them stew for two minutes. Nobody blew up at me, but some people looked nervous and upset. A lot of eye rolls. People crossed their arms."
Unsurprisingly, when the participants were asked to fill out questionnaires on their emotions and the quality of the experiment, it was pretty negative.
But the researchers found that the hungry participants felt much greater unpleasant emotions like stress and hate. (To be honest, we don't really blame them.)
However, those differences disappeared in the group that focused on their emotions beforehand, showing that by thinking about your emotions, you might be able to remove the edge off hanger.
"Simply [by] taking a step back from the present situation and recognising how you're feeling, you can still be you even when hungry," MacCormack said.
There are obviously a few limitations to this study. For one, it only looked at Americans, so we can't tell if these 'hangry' issues exist across the world.
Secondly, at least in the online component, people self-reported their hunger, and you might be more likely to report that you're really hungry if you are also prone to full-on hanger.
However, despite this, it is an interesting look at how our environment and personality might be more likely to make us hangry.
"Our bodies play a powerful role in shaping our moment-to-moment experiences, perceptions and behaviors - whether we are hungry versus full, tired versus rested or sick versus healthy," says MacCormack.
And if you are feeling a little grumpy, take a step back and think about your emotions for a bit - it might help you from turning into a hangry mess.
The research has been published in Emotion.